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thesis entitled

GAIT CHARACTERISTICS EXHIBITED BY SUBJECTS
WITH UNINJURED AND INJURED KNEES
UNDER UNFATIGUED AND FATIGUED CONDITIONS

presented by

Claudia Alejandra Angeli

has been accepted towards fulfillment
of the requirements for

Master of Science Jegreein Physical Education
and Exercise Science

 

 

Major professor

Date 11/27/1996

 

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

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MSU IsAn Affirmative AettonlEqual OppOI‘IIMIIV trunnion
Wt

GAIT CHARACTERISTICS EXHIBITED BY SUBJECTS
WITH UNINJURED AND INJURED KNEES
UNDER UNFATIGUED AND FATIGUED CONDITIONS
By

Claudia Alejandra Angeli

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Physical Education and Exercise Science

1996

ABSTRACT
GAIT CHARACTERISTICS EXHIBITED BY SUBJECTS
WITH UNINJURED AND INJURED KNEES
UNDER UNFATIGUED AND FATIGUED CONDITIONS
By

Claudia Alejandra Angeli

The purpose of the study was to perform a three dimensional kinematic analysis
to examine the effects of muscle fatigue on gait characteristics of individuals with ACL
reconstruction, compared to uninjured individuals. Subjects were tested under unfatigued
and fatigued conditions. Fatigue was produced utilizing a submaximal bicycle ergometer
test. In addition, electromyographic patterns of quadriceps and hamstrings firings were
analyzed.

The ACL group exhibited greater muscular activity when unfatigued and
fluctuated between lower and higher magnitudes of measured linear and angular
parameters when fatigued, than did the control group. Under fatigue, changes in gait
characteristics were found for all subjects in the study, with higher magnitudes in angular

parameters, when compared to the unfatigued condition.

COPyright by
Claudia A. Angeli
1 996

To my parents, Jorge and Mirna Angeli for believing in my dreams, and for all the
sacrifices and constant support.

iv

ACKNOWLEDGMENTS

Special thanks to my major professor, Dr. Ulibarri for all the good advise, unconditional
support and belief in my ability to succeed. Thanks for taking the time to listen and for
all the encouragement during hard times.

Thanks to my committee members for all the good advise.

Thanks to family and friends for the constant support and encouragement.

Thanks to Dan Wilson for letting me borrow the EMG surface electrodes.

TABLE OF CONTENTS

LIST OF FIGURES

INTRODUCTION .................................................................................

II. GAIT SEQUENCE AND TIMING ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
III. MUSCLE FATIGUE

ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
.............................................................................
oooooooooooooooooooooooooooo
ooooooooooooooooooooooooooooo

ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

A. Normal Angular Displacement Data ,,,,,,,,,,,,,,,,,,,,,,

B. Control Group ..........................................................

C. ACL Reconstructed Group ......................................
II. LINEAR MOTION

B. Control Group ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
C. ACL Reconstructed Group ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

vi

HI. SUGGESTIONS FOR FUTURE STUDIES 110

LIST OF REFERENCES ...................................................................... 113
APPENDIX A- Informed Consent Form ............................................. 117
APPENDIX B- Anthropometric Data Sheet ........................................ 119
APPENDIX C- F atiguing Protocol ....................................................... 120
APPENDD( D- User’s Guide to the Ariel Performance Analysis

System .................................................................................................... 122
APPENDIX E- Subject’s Data Sheet ................................................... 131
APPENDIX F- Angular Motion ........................................................... 134

vii

LIST OF FIGURES

Figure l. Gait Cycle Components ......................................................... 10
Figure 2. Anatomy of theRight Knee Joint __________________________________________ 15
Figure 3. Temporal Gait Cycle Components ....................................... 19
Figure 4. Testing Setup .......................................................................... 40
Figure 5. Calibration Structure ............................................................. 41
Figure 6. Digitization Order .................................................................. 43

Figure 7. Knee Flexion/Extension Angular Displacement. Normal
Pattern ..................................................................................... 48
Figure 8. Knee Abduction/Adduction Angular Displacement.
Normal Pattern ....................................................................... 49
Figure 9. Muscular Activity Patterns for the Quadriceps and
Hamstrings Muscle Groups. Normal Data ............................ 51

Figure 10. Knee Flexion/Extension Angular Displacement under
the Unfatigued Condition. Control Group .......................... 53

Figure 11. Knee Flexion/Extension Angular Velocity under the
Unfatigued Condition. Control Group ................................ 54

Figure 12. Knee Flexion/Extension Angular Acceleration under
the Unfatigued Condition. Control Group .......................... 55

Figure 13. Knee Abduction/Adduction Angular Displacement under
the Unfatigued Condition. Control Group .......................... 56

Figure 14. Knee Abduction/Adduction Angular Velocity under
the Unfatigued Condition. (a) Subject 1 (b) Subject 3 57

viii

Figure 15.

Figure 16.

Figure 17.

Figure 18.

Figure 19.

Figure 20.

Figure 21.

Figure 22.

Figure 23.

Figure 24.

Figure 25.

Figure 26.

Figure 27.

Figure 28.

Knee Abduction/Adduction Angular Acceleration under
the Unfatigued Condition. (a) Subject 1 (b) Subject 3.... 57

Knee Flexion/Extension Angular Displacement under

the F atigued Condition. Control Group .............................. 59
Knee Flexion/Extension Angular Velocity under the
Fatigued Condition. Control Group .................................... 6O
Knee Flexion/Extension Angular Acceleration under

the Fatigued Condition. Control Group .............................. 61
Knee Abduction/Adduction Angular Displacement under
the Fatigued Condition. Control Group .............................. 62

Knee Abduction/Adduction Angular Velocity under
the Fatigued Condition. (a) Subject 1 (b) Subject 3. ........ 63

Knee Abduction/Adduction Angular Acceleration under
the Fatigued Condition. (a) Subject 1 (b) Subject 3. ________ 64

Muscular Activity Patterns for the Quadriceps and
Hamstrings Muscle Groups under the Unfatigued
Condition. (a) Subject 2 (b) Subject 3. .............................. 65

Muscular Activity Patterns for the Quadriceps and
Hamstrings Muscle Groups under the F atigued
Condition. (a) Subject 2 (b) Subject 3. .............................. 66

Knee F lexion/Extension Angular Displacement under
the Unfatigued Condition. ACL-reconstructed Group ...... 68

Knee Flexion/Extension Angular Velocity under the
Unfatigued Condition. (3) Subject 4 (b) Subject 5. __________ 69

Knee Flexion/Extension Angular Acceleration under
the Unfatigued Condition. (a) Subject 4 (b) Subject 5.__" 7O

Knee Abduction/Adduction Angular Displacement under
the Unfatigued Condition. ACL-reconstructed Group ...... 71

Knee Abduction/Adduction Angular Velocity under
the Unfatigued Condition. (a) Subject 4 (b) Subject 5-.... 72

ix

Figure 29. Knee Abduction/Adduction Angular Acceleration under
the Unfatigued Condition. (a) Subject 4 (b) Subject 5.... 73

Figure 30. Knee F lexion/Extension Angular Displacement under
the Fatigued Condition. ACL-reconstructed Group .......... 74

Figure 31. Knee Flexion/Extension Angular Velocity under the
Fatigued Condition. (a) Subject 4 (b) Subject 5. .............. 75

Figure 32. Knee F lexion/Extension Angular Acceleration under
the Fatigued Condition. (a) Subject 4 (b) Subject 5. ________ 76

Figure 33. Knee Abduction/Adduction Angular Displacement under
the Fatigued Condition. ACL-reconstructed Group .......... 77

Figure 34. Knee Abduction/Adduction Angular Velocity under
the Fatigued Condition. (a) Subject 4 (b) Subject 5 _________ 78

Figure 35. Knee Abduction/Adduction Angular Acceleration under
the F atigued Condition. (a) Subject 4 (b) Subject 5 ......... 78

Figure 36. Muscular Activity Patterns for the Quadriceps and
Hamstrings Muscle Groups under the Unfatigued
Condition. Subject 4. (a) Trial 1 (b) Trial 2 ...................... 79

Figure 37. Muscular Activity Patterns for the Quadriceps and
Hamstrings Muscle Groups under the F atigued
Condition. Subject 4. ........................................................... 80
Figure 38. Joint Alignment ____________________________________________________________________ 82

Figure 39. Linear Displacement under the Unfatigued Condition.
(a) Control Group (b) Subject 2 ......................................... 84

Figure 40. Linear Velocity under the Unfatigued Condition.
Control GIOUP ...................................................................... 35

Figure 41. Linear Acceleration under the Unfatigued Condition.
Control Group ...................................................................... 86

Figure 42. Linear Displacement under the Fatigued Condition.
(a) Control Group (b) Knee-hip Comparison under the
F atigued Condition (c) Knee-hip Comparison under the
Unfatigued Condition .......................................................... 87

Figure 43. Linear Velocity under the F atigued and Unfatigued
Conditions. Control Group. (a) Fatigued (b) Unfatigued__ 89

Figure 44. Linear Acceleration under the Fatigued and Unfatigued
Conditions. Control Group. (a) F atigued (b) Unfatigued" 89

Figure 45. Linear Displacement under the Unfatigued Condition.
(3) Subject 4 (b) Subject 2 - Control Group (c) Subject 5
(c) Control Group ................................................................. 91

Figure 46. Linear Velocity under the Unfatigued Condition.
(a) Subject 4 (b) Subject 5 (c) Control Group ................... 94

Figure 47. Linear Acceleration under the Unfatigued Condition.
(a) Subject 4 (b) Subject 5 (c) Control Group ................... 95

Figure 48. Linear Displacement under the Fatigued and Unfatigued
Conditions. (21) Subject 4 - F atigued (b) Subject 4 -
Unfatigued (c) Subject 5 - F atigued (d) Subject 5 -
Unfatigued ____________________________________________________________________________ 97

Figure 49. Linear Velocity under the Fatigued and Unfatigued
Conditions. (a) Subject 4 - Fatigued (b) Subject 4 -
Unfatigued (c) Subject 5 - Fatigued ((1) Subject 5 -
Unfatigued ............................................................................ 98

Figure 50. Linear Acceleration under the Fatigued and Unfatigued
Conditions. (a) Subject 4 - F atigued (b) Subject 4 -
Unfatigued (c) Subject 5 - Fatigued (d) Subject 5 -

Unfatigued ............................................................................ 100
Figure 51. Placement of Targets Using Triads .................................... 111
Figure 52. Suggested Testing Setting Using Three Cameras .............. 112

Figure 1E: Knee Flexion/Extension Angular Displacement.
Subject 1 (a) Unfatigued Trials (b) Fatigued Trials 134

.........

xi

Figure 2E: Knee Flexion/Extension Angular Displacement.

Subject 2 (a) Unfatigued Trials (b) Fatigued Trials _________ 134
Figure 3E: Knee Flexion/Extension Angular Displacement.

Subject 3 (a) Unfatigued Trials (b) Fatigued Trials ......... 135
Figure 4E: Knee Flexion/Extension Angular Displacement.

Subject 4 (a) Unfatigued Trials (b) Fatigued Trials ......... 135
Figure 5E: Knee Flexion/Extension Angular Displacement.

Subject 5 (a) Unfatigued Trials (b) Fatigued Trials _________ 135

Figure 6E: Knee F lexion/Extension Angular Velocity. Subject 1
(a) Unfatigued Trials (b) Fatigued Trials ........................... 136

Figure 7E: Knee Flexion/Extension Angular Velocity. Subject 2
(a) Unfatigued Trials (b) Fatigued Trials ........................... 136

Figure 8E: Knee Flexion/Extension Angular Velocity. Subject 3
(a) Unfatigued Trials (b) Fatigued Trials ___________________________ 136

Figure 9E: Knee Flexion/Extension Angular Velocity. Subject 4
(a) Unfatigued Trials (b) F atigued Trials ........................... 137

Figure 10E: Knee Flexion/Extension Angular Velocity. Subject 5
(a) Unfatigued Trials (b) F atigued Trials ___________________________ 137

Figure 11E: Knee Flexion/Extension Angular Acceleration.
Subject 1 (a) Unfatigued Trials (b) Fatigued Trials ....... 137

Figure 12E: Knee Flexion/Extension Angular Acceleration.
Subject 2 (a) Unfatigued Trials (b) Fatigued Trials _______ 138

Figure 13E: Knee Flexion/Extension Angular Acceleration.
Subject 3 (a) Unfatigued Trials (b) Fatigued Trials ....... 138

Figure 14E: Knee F lexion/Extension Angular Acceleration.
Subject 4 (a) Unfatigued Trials (b) Fatigued Trials ....... 138

Figure 15E: Knee Flexion/Extension Angular Acceleration.
Subject 5 (a) Unfatigued Trials (b) Fatigued Trials ....... 139

xii

Figure 16E:

Figure 17E:

Figure 18E:

Figure 19E:

Figure 20E:

Figure 21E:

Figure 22E:

Figure 23E:

Figure 24E:

Figure 25E:

Figure 26E):

Figure 27E:

Figure 28E:

Figure 29E:

Knee Abduction/Adduction Angular Displacement.
Subject 1 (a) Unfatigued Trials (b) Fatigued Trialsm

Knee Abduction/Adduction Angular Displacement.
Subject 2 (a) Unfatigued Trials (b) Fatigued Trials."

Knee Abduction/Adduction Angular Displacement.
Subject 3 (a) Unfatigued Trials (b) F atigued Trials."-

Knee Abduction/Adduction Angular Displacement.
Subject 4 (a) Unfatigued Trials (b) Fatigued Trials".

Knee Abduction/Adduction Angular Displacement.
Subject 5 (a) Unfatigued Trials (b) Fatigued Trialsw

Knee Abduction/Adduction Angular Velocity.

Subject 1 (a) Unfatigued Trials (b) Fatigued Trials”.

Knee Abduction/Adduction Angular Velocity.

Subject 2 (a) Unfatigued Trials (b) Fatigued Trials”.

Knee Abduction/Adduction Angular Velocity.

Subject 3 (a) Unfatigued Trials (b) Fatigued Trials."

Knee Abduction/Adduction Angular Velocity.

Subject 4 (a) Unfatigued Trials (b) F atigued Trials____

Knee Abduction/Adduction Angular Velocity.

Subject 5 (a) Unfatigued Trials (b) Fatigued Trials".

Knee Abduction/Adduction Angular Acceleration.

Subject 1 (a) Unfatigued Trials (b) Fatigued Trials“.

Knee Abduction/Adduction Angular Acceleration.

Subject 2 (a) Unfatigued Trials (b) Fatigued Trials".

Knee Abduction/Adduction Angular Acceleration.

Subject 3 (a) Unfatigued Trials (b) F atig'ued Trials"-

Knee Abduction/Adduction Angular Acceleration.

Subject 4 (a) Unfatigued Trials (b) Fatigued Trials".

xiii

139

139

140

140

140

141

141

141

142

142

142

143

143

143

Figure 30E: Knee Abduction/Adduction Angular Acceleration.
Subject 5 (a) Unfatigued Trials (b) Fatigued Trials ....... 144

xiv

CHAPTER I

INTRODUCTION

Interest in healthy lifestyles has caused an increase in the number of physically
active individuals in the United States. Along with a greater level of activity, there has
been an increase in the number of injuries reported. The leading cause of sports injuries
is overuse (Pecina and Bojainc, 1993). Statistics show that soccer, tennis and football are
the sports in which the majority of all the knee injuries occur (Nicholas and Hershman,
1995). Within the broad category of knee injuries, the anterior cruciate ligament (ACL)
and the medial colateral ligamnet (MCL) are the most commonly injured tissue of the
joint, responsible for over 50% of the injuries reported. Because of the anatomy of the
knee, an injury to the anterior cruciate ligament is often accompanied by an injury to
other soft tissues of the joint. Most injuries to the knee ligaments occur due to some type
of contact or force which produces an abnormal movement at the joint. Non contact
injuries to the ACL are produced by abnormal loading of the knee joint during landing in
an unbalanced position (Nicholas et al., 1995).

While the cruciate ligaments guide and restrict the tibia and femur to a gliding

and sliding motion, the anterior cruciate ligament is the primary stabilizer of the knee

2
joint (Jackson and Drez, 1987). An injury to the anterior cruciate ligament negates

normal function, and jeopardizes joint stability. Ligament sprains are classified into three
categories: first degree, in which the ligament fibers are injured at the microscopic level,
and no stability is lost in the joint; second degree, a partial tear of the ligament fibers
occurs, and some joint stability is compromised; and third degree, in which the ligament
fibers are completely torn, accompanied by a complete loss of stability (Macnicol, 1986).
Several factors will determine the treatment following the injury: severity of the tear, age
of the patient, level of activity of the patient, and desire to continue an active lifestyle.
Reconstruction of the ACL is usually recommended for second and third degree tears,
and for individuals who plan to continue a high level of activity. Rehabilitation without
surgical intervention is often sought by individuals who do not plan to engage in high
levels of activity, or have experienced a first degree sprain to the ACL, without any
damage to other knee structures (Jackson and Drez, 1987).

Further consideration should be given to the issue of ACL reconstruction versus
rehabilitation. The consequences of an injury to the ACL include loss of knee stability as
well as modifications to the knee mechanics. Considering these factors, ACL
reconstruction should focus on restoring knee stability, maintaining the normal
mechanics of the knee joint, and preventing the premature degeneration of the joint. The
surgical procedure for reconstruction is beyond the scope of this paper. However, it is
important to understand that replacement for the anterior cruciate ligament must exhibit
similar mechanical characteristics as the original ACL in order to allow for the same joint

kinematics.

3
Chronic ACL deficiency may result from untreated injuries to the ACL. If the

patient decides only to rehabilitate the knee after the injury, chronic knee laxity can
become a factor. Jackson and Drez (1987), identified most chronic ACL deficient
patients as having laxity greater than 7.5 millimeters in the injured knee and a difference
greater than 2 millimeters between both lower limbs. The authors also reported that
repairs of acute ACL injuries surgically treated soon after the incident had a 6% better
outcome than repairs performed on chronically deficient knees. As a result of frequent
subluxation of the joint in the ACL deficient knee, other tissues may become damaged; if
surgery is desired at this point, the results may not be as successful since degeneration of
the tissue has already began.

The knee kinematics are compromised as a consequence of an injury to the
anterior cruciate ligament. In addition, muscle action is altered to compensate for
abnormal movements (Shiavi, Zhang, Limbird, and Edmondstone, 1992). The topic of
injuries to the anterior cruciate ligament has been of interest to several investigators
Andriacchi (1990 and 1993); Timoney, Inman, Quesada, Sharkey, Barack, Skinner and
Alexander (1993); Berchuck, Andriacchi, Bach, and Reider (1990), who all used gait
analysis to examine the adaptations caused by an ACL injury. The general results of
these studies showed differences in angular displacement at the knee joint. Other research
has focused on change in muscle action due to the injury (Shiavi, Zhang, Limbird, and
Edmondstone, 1992; Schipplein and Andriacchi, 1991; Solomonow, Baratta, Zhou,

Shoji, Bose, Beck, and D’Ambrosia, 1987; Hirokawa, Solomonow, Lu, Lou, and

4
D’Ambrosia, 1992; Renstrom, Arms, Stanwyck, Johnson, and Pope, 1986; and

O’Connor, 1993).

Even though the topic of anterior cruciate ligament injuries has been very popular
in the past two decades, little, if any, importance has been given to the issue of fatigue in
relation to an ACL injury. Muscle fatigue can play an important role in the reoccurrence
of any type of injury. In the case of an ACL injury, muscle involvement becomes a
critical factor in the early stages of the rehabilitation process. When a second degree
injury occurs, the anterior cruciate ligament has an 86% reduction in its capacity to
restrain joint movements (Jackson and Drez, 1987). With a reduction in knee stability
produced by the injured ACL, the muscles assume a more important role in knee function

(McNair and Wood, 1993).

I. NEED FOR THE STUDY

Research in the area of muscular fatigue as it relates to gait characteristics is rare.
Studies in which the effects of fatigue on the function of muscles as primary stabilizers
of the knee after an injury to the anterior cruciate ligament are scarce. When the anterior
cruciate ligament is injured, knee stability is jeopardized. In combination with the
kinematic adaptations present at the knee joint, muscles of the lower extremity become
joint stabilizers, restricting excessive movement of the bones (Jackson and Drez, 1987).
After a period of approximately six to nine months, the individual is usually ready to

return to preinjury activity level. However, gait analysis studies have shown that

5
adaptations in the patients’ walking characteristics are still present after one year of the

injury (Andriacchi, 1990; Andriacchi, 1993; Berchuck et al., 1990).

Return to physical activity prior to full restoration of the mechanical properties of
the injured ligament can increase the chances of reinjury. Noyes, Torvik, Hyde, and
DeLucas, (1976) reported a 39% decline in the maximum failure load of the ligament
after an eight week period of immobilization. There were no additional benefits of
isometric exercises during the immobilization period. Afier 20 weeks of rehabilitation
exercises, the ligament showed almost normal stiffness properties, but strength properties
were incomplete. Athletes and coaches must be sensitive to the results obtained by Noyes
et a1. (1976), as these results have implications for preventing ligament reinjury and
further damage to the joint itself.

There has been little research performed on the effects of fatigue on reinjury of
the anterior cruciate ligament. Injury to the anterior cruciate ligament is one of the most
common injuries to the lower extremity in competitive sports. Muscle fatigue becomes a
concern due to the role of the muscles of the lower extremity as primary stabilizers of the
joint. The athletes’ training styles do not typically change after returning from a
rehabilitation period (S. Nogle, personal communication, March 21, 1996). Long hours
of intense workout have always been a characteristic of training, and have not been
thought as a situation in which the athlete is at risk of injury.

The lack of studies in which fatigue is considered as a variable to the kinematic
analysis of an injury related situation, can be due to the controversy of the topic. Fatigue

has been a very poorly undersde topic, due to its complexity in physiological

6
characteristics, as well as the lack of understanding of the psychological effects at its

onset. Most of the research done on fatigue is to gain a better understanding from a
physiological point of view. Research conducted on the effects of fatigue on the
kinematic characteristics of uninjured and injured individuals can assist in the
development of safer training practices for injured individuals. This study will focus on
the kinematic characteristics of individuals with an anterior cruciate ligament
reconstruction not older than 15 months, under fatigued and unfatigued states of the
muscles of the lower extremity. The same kinematic characteristics and the adaptations

due to fatigue will be analyzed in uninjured individuals.

H. PURPOSE OF TIDE STUDY

Kinematic adaptations during gait of individuals with ACL deficiency or recent
reconstruction have been well documented (Andriacchi, 1990 and 1993; Timoney et al.,
1993; Tibone, Antich, Fanton, Moynes and Perry, 1986; and Berchuck et al., 1990).
Functional changes in the knee joint as a result of the injury to the ACL, are exhibited in
gait analysis data as well as electromyographical (EMG) data. The purpose of this study
was to perform a three dimensional kinematic analysis utilizing EMG in order to
examine the effects of muscle fatigue on the gait characteristics of individuals with a
reconstructed anterior cruciate ligament, and compare the changes to those experienced
by uninjured individuals. The following hypotheses were formed on the basis of previous

research:

7
Hypothesis 1: individuals with ACL reconstruction will exhibit greater muscular

activity during the stance phase under normal conditions than the control subjects.
Hypothesis 2: under the fatigued state, individuals with ACL reconstruction will
have lower angular and linear displacements, velocities and accelerations
occurring at the knee joint, than under normal conditions.

Hypothesis 3: subjects with ACL reconstruction will experience adaptations of
greater magnitudes occurring at the knee joint under the fatigued state than the

control group.

IH. ASSUMPTIONS AND LIMITATIONS

It will be assumed that each individual reaches muscle fatigue prior to each trial
under the fatigued condition, and the fatigued state is maintained throughout the trial.
Fatigue will be assumed to be present when the subject cannot maintain the
predetermined mechanical output on the bicycle ergometer, the EMG pattern decreases in
frequency and in amplitude, and the subject reaches 8 on the Borg’s 10 point perceived
exertion scale.

Due to the short duration, high intensity characteristic of the fatiguing protocol,
muscle fatigue will occur due to depletion of energy sources in the muscle. Different
factors may contribute to the onset of fatigue after long duration, moderate intensity
exercise. For this study, it will be assumed that the type of fatigue does not affect the

adaptations in gait characteristics.

IV. SIGNIFICANCE OF THE STUDY

The findings of this study will contribute to the field of injury prevention. The
study will provide information for coaches, trainers, and athletes on how the knee joint
specifically adapts to the factors of muscle fatigue after an injury to the ACL.
Understanding the changes in kinematic characteristics during gait as a consequence of
fatigue of the muscles of the lower extremity, in an individual with recent ACL
reconstruction, can help in the development of safer training practices for the injured
athlete. Understanding the effects of muscular fatigue in a healthy individual will also

allow for the planning of safer practices for prevention of injuries.

V. DEFINITIONS

Anterior cruciate ligament deficiency: a condition experienced after a partial or complete
tear of the anterior cruciate ligament. The knee joint demonstrates instability during
clinical examinations, Lachman and anterior drawer tests. Normal knee mechanics may
only be reinstated through reconstruction.

Anterior cruciate remnstruction: replacement of the injured anterior cruciate ligament
through surgical procedure, allowing a close reproduction of normal knee mechanics.
Cocontraction: simultaneous contraction of two or more muscle groups.

Concentric contraction: shortening of muscle fibers when tension is produced.
Eccentric contraction: lengthening of muscle fibers when tension is produced.
Electrgmyoggaphy: (EMG) method use for measuring electrical signals during muscle

activity. Surface electrodes will be used as sensing devices.

9
Fatigpe: inability of the muscle to maintain a constant mechanical output at

approximately 75% of maximum workload.
Gait cycle: cycle which refers to the period between heelstrike of one limb to heelstrike
of the same limb. Each cycle is composed of the following events (see Figure 1):
Heelstrike (HS): beginning of the stance phase, when the foot first makes contact
with the ground.
Midstance: point at which deceleration changes to acceleration. The position of the
shank is at 90 degrees to the surface.
Mpg (TO): end of the stance phase, when the foot leaves the contact surface as it
enters the swing phase.
Stance phase: period during the gait cycle in which the limb is in contact with the
ground. This period starts with heelstrike of either foot and ends with toe off of the
same foot. The stance phase can be divided into two events:
Single suppprt phase: period during the gait cycle in which one limb is in
contact with the ground and the opposite limb is in the swing phase.
Double support phase: period during the gait cycle in which both limbs are in
contact with the ground.
Swing phase: period during the gait cycle in which the limb is advancing free of

contact with the ground. This period starts at toe ofi’ and ends at heelstrike.

AAAJMMA

 

 

 

Right Stance Right Swing
II I L
Left Stance Left Swing Left Stance
Double Support Double Support

Figure 1: Gait Cycle Components

Knee stability: restriction of excessive joint motion. The values of laxity tests are within
the normal range.

Ligament tear: injury to the ligamentous tissue. The following classification specifies the
severity of the injury:

First degree tear: injury to the ligament fibers at the microscopic level. No joint

instability is detected during clinical examinations.

Second degzee t_e_ar,_: partial injury to the ligament fibers. Increased instability may be

detected during clinical examinations.

Third deggee tear: complete tear of the ligament fibers. All joint stability is lost.
Normal gait: walking pattern kinematics within normal ranges and demonstrating no
characteristics and signs of injury.

Stride lengmz distance between heel contact of one foot to heel contact of the same foot

after a complete cycle. The distance is measured in the sagittal plane.

1 1
Valg1_1_s deformity: medial opening at the knee joint.

Varus deformity: lateral opening at the knee joint.

CHAPTER H

REVIEW OF LITERATURE

Walking is one of the most common locomotive activities performed by humans.
Analysis of the components of gait of the lower extremity can assist in the identification
of pathological conditions. A kinematic gait analysis provides information about linear
and angular displacements, velocities, and accelerations, which can be used in the
detection of variations in walking. Kinetic data can complement the kinematic analysis
by providing information about forces, moments, and power. Aside from individual
differences in the gait data, adaptations made because of a pathological condition can be
identified by the discrepancies in the kinematic values when compared to range values
of data from non pathological subjects. From the digitization of markers placed over the
specific joint, a biomechanical model can be developed. Angular and linear calculations
can be made from the data collected, with body position being determined first, followed
in order by velocity and acceleration calculations. The kinematic data can be combined
with data from force plates, electromyographs, and electrogoniometers, which enrich the
analysis (Harris and Wertsch, 1994).

Patterns of walking have not been found to be mechanically predetermined,

suggesting that the step length and frequency during walking can be changed if desired.

12

13
As these changes are made, the walking pattern must always meet the prerequisites of

equilibrium, body stability, and strength to maintain a coordinated movement. Another
characteristic of normal gait is the symmetry of movement with right and left steps being
approximately the same length. After the age of four, the actions involved in walking
start to become automatic and the movements are controlled by the central nervous
system. The central nervous system produces a basic locomotion pattern which is
intended to propel the body in a specific direction, controls the balance of the body and
adapts the gait pattern to different environmental demands. Changes in the environment
as well as changes within the locomotive system result in adaptations to the gait pattern.
Adaptations of any of the components of the gait pattern are made to maintain both body
balance and gait mechanics close to the normal range for that individual (Zatsiorky,
Werner, and Kaimin, 1994).
I. KNEE ANATOMY

A brief review of the structure of the knee joint will be provided to facilitate the
understanding of the studies reviewed in this chapter. The femur and the tibia articulate
in a hinge joint, which has as part of the supportive structure, dense connective tissue
called the cruciate ligaments. The ACL is attached to the posterior aspect of the medial
surface of the lateral femoral epicondyle. At the tibia, it attaches to a fossa, anterior and
lateral to the anterior tibial spine. As it attaches to the tibia, the ACL passes under the
transverse meniscal ligament, and a few fascicles of the ligament may blend with the
anterior part of the lateral meniscus. This blending of tissues is often the reason for injury

to the ACL. The posterior cruciate ligament (PCL) is attached to the posterior aspect of

14
the lateral surface of the medial femoral epicondyle. At the tibia, the PCL attaches to the

depression found posteriorly on the articular surface of the tibia. The cruciate ligaments
cross each other anteriorly and posteriorly, as they extend from the femur to the tibia.
This orientation in space is critical to the firnction of the cruciate ligaments as they serve
to constrain anterior/posterior joint motion. The anterior cruciate ligament extends
anteriorly, medially, and distally as it crosses from the femur to the tibia. The ACL also
turns into a small outward spiral, due to the attachment sites. The posterior cruciate
ligament, extends posteriorly, laterally, and distally through the joint, as shown in
Figures 2a, 2b and 2c. The orientation of the femoral attachments is responsible for the
ligament’s tension throughout the range of motion. Both ligaments act to limit extension,
and prevent hyperextension at the knee joint. If the knee reaches a hyperextended
position, the ligament that is most exposed to an injury is the anterior cruciate (F eagin,
1988). The menisci rest on the head of the tibia, and articulate with the epicondyles of
the femur, as shown in Figure 2c. Each cartilage is attached to the inside aspect of the
capsule in the knee. Each meniscus covers the outer two-thirds of the articulating surface
of the tibia. The medial meniscus is semicircular; its anterior aspect is attached to the
depression on the anterior margin of the head of the tibia. Its posterior aspect is attached
to the depression behind the spine of the tibia. The lateral meniscus is almost a full circle,
and covers a larger surface than the medial meniscus. The anterior portion of the lateral
meniscus is attached anteriorly to the spine of the tibia, and the posterior aspect of the

lateral meniscus is attached behind the spine (Gray, 1974).

 

LAnterior Cmciate Ligament

 

 

Posterior Cruciate Ligament |

 

 

L Fig. 2a: Right Knee - Medial view of Sagittal View J

 

  
   
 
  

 

 

I Posterior Cruciate Ligament ]

 

Anterior Cruciate Ligament]

 

 

 

Anterior Cnlciate Ligament

Medial Meniscus

 

lPosterior Cruciate Ligament l

 

 

I Fig. 3c: Right Knee - Transverse View of Tibial Plateau |
Figure 2: Anatomy of the Right Knee Joint

 

16
One of the principal issues that needs to be addressed when analyzing gait of

individuals with ACL deficiency, is the functional level of the knee joint. The role of the
anterior cruciate ligament is to stabilize the knee joint. The ACL is the main ligament
responsible for the prevention of anterior displacement of the tibia over the femur, and it
also aids in restricting hyperextension. As a result of an injury to this major stabilizer,
the knee joint is subject to rotational and shear moments which can further jeopardize the
joint’s functional capabilities (Shiavi, Zhang, Limbird, and Edmondstone, 1992). An
injury to soft tissue in the joint results in mechanical adaptations to compensate for
functional losses (Peltier, 1985).

An injury to the anterior cruciate ligament produces adaptations in the function of
the knee joint. To be able to isolate these adaptations, the normal behavior of the
ligament must be observed under different conditions. The following measurements were
obtained during a study done on cadavers, with the purpose to measure strain in the
anterior cruciate ligament during different positions of the knee joint. The tool used for
this purpose was a Hall effect transducer. Full extension was defined as a flexion angle of
0 degrees. The minimum strain of the anterior cruciate ligament during a normal
flexion/extension pattern was found at 30 to 35 degrees; under a passive motion, the
strain level decreased. Flexion greater than 35 up to 120 degrees, increased the strain
level. At about 15 to 45 degrees of flexion, the anterior cruciate ligament showed its
greatest strain during a passive varus moment, defined as a rotation towards the midline
of the body. The passive valgus moment, causing a rotation of the tibia away from the

midline of the body, also produced increased levels of anterior cruciate ligament strain,

17

except during full knee extension. When passive internal and external rotations were
compared for the anterior cruciate ligament strain increase, the internal rotation was more
significant, maximizing at 10 to 15 degrees of flexion and showing its minimum effect at
60 to 65 degrees. When an isometric quadriceps contraCtion was simulated, the anterior
cruciate ligament strain increased significantly over the first 45 degrees of flexion and
the strain decreased when the angle of flexion was more than 60 degrees. An eccentric
contraction of the quadriceps also showed a significant strain increase for the first 45
degrees of flexion, and appeared to be similar to the normal pattern when the angle was
greater than 7 0 degrees. When movement of external rotation combined with an eccentric
contraction which lowered the leg, decreased levels of anterior cruciate ligament strain
were demonstrated. The measurements show that the ACL tightens when the knee is in
maximum flexion to approximately 35 degrees of flexion, and relaxes from 35 degrees of
flexion to full extension (Arms, Pope, Johnson, Fischer, Arvidsson, and Eriksson, 1984).
In addition to the information on knee structure, the fundamental characteristics
of knee mechanics also need to be included in the discussion. When the body is resting in
a supine position, the only stress on the knees is produced by the generation of muscular
force. On the other hand, when the body is in a standing position, the knee joint is
supporting a large percentage of the body weight. Ifthe line of action of this force does
not pass directly through the center of the knee, the muscle forces must compensate to
keep the body balanced. As the subject engages in walking, the center of gravity is rarely
over the supporting foot during the single support phase of the gait cycle. To overcome

this imbalance, dynamic equilibrium is achieved through the forces of inertia generated

18
by accelerations and decelerations of the body (Maquet, 1984). The muscles of the three

joints of the lower extremity act to maintain the body balance during the support phase.
When one joint opposes the supporting action of the limb, the other two joints perform

compensating actions to maintain stability and support (Winter, 1980).

II. GAIT SEQUENCE AND TIMING

Understanding the sequence and timing of the gait phases is critical for a correct
analysis. Walking is characterized by a series of repetitive actions which constitute the
gait cycle. A cycle starts with heel contact of one limb and ends with heel contact of the
same limb (see Figure 3). The gait cycle can be divided into two major phases: the stance
and the swing phases. The stance phase begins with heel strike, then the body weight
progressively shifts over the support limb until the end of stance phase at toe off. The
stance phase lasts for approximately 60% of the gait cycle. During both the initial and
final portions of the stance phase there is a period of double support, in which both limbs
are in contact with the ground. The swing phase begins at toe off and continues until heel
contact. The swing phase makes up the other 40% of the gait cycle (Harris and Wertsch,

1994; Valmassy, 1995).

AMMMM}

 

 

RightStance ' Right swing
II | I
Left Stance Lefi Swing Lefi Stance
Double Support Double Support

Figure 3: Temporal Gait Cycle Components

The period in which the limb is in contact with the ground is the most important
for gait analysis because of the variability in gait patterns observed during this phase.
Valmassy (1995) further subdivided the stance phase into four functional phases. The
first phase, defined as the contact phase, is initiated as the heel contacts the ground and
continues until the opposite limb’s toe off. The midstance phase, starts with toe off of the
opposite limb and continues until the heel lifts from the support limb. The third phase is
the active propulsion phase, in which the opposite limb completes the stride by
contacting the ground. And the last phase is passive lift off, which starts from heel
contact of the opposite limb until toe off of the support foot. Both the first and fourth
phases are double support phases. The contact phase is a period of deceleration, as the
limb completes the swing phase and prepares to support the body. During the passive lift
off, the body decelerates transferring the weight to the opposite limb which has made

contact with the ground.

20
As the heel makes contact with the ground and throughout the contact phase,

specific actions occur in the lower extremity which are characteristic of normal walking.
During this period the hip extends, while the knee flexes and the ankle rapidly plantar
flexes. The ankle plantar flexion results in a rapid forward displacement of the tibia and
a slower movement of the femur, creating knee flexion. At heel contact, the knee is fully
extended and it progressively flexes approximately 15 to 18 degrees throughout this
phase. Both the actions at the knee and ankle joints are responsible for most of the shock
absorption that occurs at contact. The quadriceps and hamstrings are active during this
period to aid in knee stability. The quadriceps act to prevent excessive and rapid flexion,
while the hamstrings resist hyperextension (V almassy, 1995).

The functional changes observed during the contact phase due to an injured ACL
were explained by Andriacchi (1993) and Ciccotti, Kerlan, Perry, and Pink (1994).
Quadriceps avoidance gait was found to be a common adaptation during the initial part of
the stance phase among individuals with ACL reconstruction and ACL deficiency.
Quadriceps avoidance gait is initially observed during the contact phase when knee
flexion is absent. Since knee extension is predominant throughout the support phase of
the gait cycle, the demand on the quadriceps is reduced by the lack of knee flexion.
Under normal circumstances, the quadriceps eccentrically contract during the contact
phase, to balance gravitational forces at the knee. With the loss of the normal function of
the ACL, a quadriceps contraction when the knee is near full extension would cause an

anterior displacement of the tibia over the femur. Due to the prolonged knee extension

21

observed in the injured knee group, the quadriceps produced a lower than normal net
moment, to prevent the tibia from displacing anteriorly (Andriacchi, 1993).

A similar comparison of the gait patterns of subjects with an injury to the ACL,
and a control group was performed by Timoney, Inman, Quesada, Sharkey, Barrack,
Skinner, and Alexander (1993). The objective of the study was to identify the adaptations
which resulted from the injury and subsequent reconstruction. The injured group
demonstrated an external flexion moment during the contact and midstance phases of the
gait cycle. This external flexion moment would lead to an internal extension moment
produced by the quadriceps, conflicting with the theory of quadriceps avoidance gait
mentioned earlier. The external flexion moment was found to be lower when compared
to the control group, which still demonstrated an adaptation during the contact phase of
the gait cycle. Another change experienced by the injured group was a slower loading
rate during heel strike. This adaptation was interpreted by the authors as the care taken by
the patient when stress was applied to the knee.

Similar adaptations were found in a study performed by Schipplein and
Andriacchi (1991), in which they analyzed the interaction of the passive and active
stabilizers during walking. The population which took part in this study consisted of
patients with varus deformity. The authors calculated joint reaction forces, soft tissue
tension, and muscle forces using a mathematical model. Dynamic lateral stability was
observed during walking. Stability during walking was assisted by antagonistic muscle
action, which helped maintain balance and prevent lateral opening of the joint. The

patient group demonstrated a period of either complete flexion or extension during the

22
stance phase, as opposed to two clear periods of flexion demonstrated in the control

group. Pretension of the lateral ligaments of the knee was observed during the stance
phase in the patient population. The stance phase was shorter in the patient population
than in the control group, as the soft tissue maintained joint stability through tension
increasing the strain in the soft tissues. The results of this study showed that a minimum
muscle force, without antagonistic action, was not enough to stabilize the knee joint
during walking. The joint needed to be stabilized dynamically by cocontraction of
antagonistic muscles, and or pretension of the lateral soft tissues.

When the single support phase is initiated, the swing leg advances from a
posterior to an anterior position relative to the support limb, requiring an increase in
stability of the contact leg as well as the trunk. During the midstance phase, extension at
the hip is continued from the previous phase, while the knee starts to extend. Extension
at the knee is produced by the slower forward displacement of the proximal tibia in
comparison to the more rapidly advancing femur. The quadriceps remain active for the
initial portion of the midstance, as they prevent flexion at the knee joint and assist in the
extension action. Extension of the leg is also assisted by eccentric contractions of the
gastrocnemius and soleus muscles (V almassy, 1995).

Active propulsion is the second portion of the single support period. During this
phase the body advances beyond the supporting limb. An external rotation of the lower
extremity is produced as the swing leg advances beyond the support leg. The knee and
hip are externally rotated during this period. As the weight of the body shifts forward, the

hip continues its extending action until hyperextension is reached. Knee extension

23

initiated during midstance is continued until near full extension prior to toe off. This
action of extension at the knee controls the lowering of the body’s center of gravity and
the stride length (V almassy, 1995).

The second period of double support starts with the opposite limb’s heel strike,
which initiates the passive lift off phase. As the support limb prepares to enter in the
swing phase, momentum of the opposite limb assists in forward advancement.
Maximum external rotation of the knee and hip are observed during this phase, as both
joints continue the rotation initiated during the active propulsion phase. The hip flexes
during this period, reaching a neutral position at toe off. The knee flexes in preparation
for leg swing. The quadriceps and hamstrings are active during this period (V almassy,
1995)

Instability in the knee joint leads to adaptations throughout functional activities.
The adaptations made during walking maintain a symmetrical gait pattern (Tibone,
Antich, Fanton, Moynes, and Perry, 1986). However, when electromyographic (EMG)
data were analyzed, different firing responses were evident in the involved and
uninvolved limbs. Electromyographic data complement the kinematic analysis and allow
further understanding of the changes in muscle activity as a result of the injury. Muscle
contractions can be very important to the stabilization of the knee joint after an ACL
injury. Muscles can actively stabilize the knee, and similarly protect it from the shear and
rotational forces that can be experienced as a result of the injury.

The use of EMG can assist in the understanding of gait characteristics. A major

concern with this procedure is the limited knowledge in the interpretation of the signals.

24

Basmajian and Deluca (1985), made an effort to explain the neurophysiological
components which relate to the field of electromyography. The authors defined the
electromyographic signal as “the electrical manifestation of the neuromuscular activation
associated with a contracting muscle” (p. 65). The signal is influenced by a set of
components from muscle properties and characteristics, to the instrumentation used for
recording and reading. An electrode located in the vicinity of the muscle fiber will
capture the action potential generated by the movement of ions and depolarization of the
post-synaptic membrane.

Several factors are important in the reading and interpretation of an
electromyographic signal. The action potential amplitude demonstrates a correlation with
the diameter of the muscle fiber, as well as a dependency on position of the recording
electrode in relation to the active muscle fiber. A greater amplitude is due to a larger
radius of the muscle fiber, and a shorter distance between the recording site and the
active muscle fiber. The tissue present between the recording site and the active muscle
fiber will create a filter effect, this phenomenon is more obvious for surface electrodes
than for indwelling electrodes. Another important factor is the action potential duration,
which demonstrates a negative correlation with the conduction velocity of the muscle
fiber. Since the recording electrode cannot detect the action potential of one muscle
fiber, the signal is a result of combined individual action potentials, commonly defined as
the motor unit action potential (Basmajian and Deluca, 1985).

One of the most difficult tasks in any biomechanical analysis is being able to

determine if movement falls outside the normal range pattern. A typical pattern will have

25

to be defined in order to highlight the differences observed as a consequence of an
external factor; in this case, an ACL injury. Researchers have made an effort to clearly
differentiate between typical and atypical gait patterns. Studies conducted by Ciccotti,
Kerlan, Perry, and Pink (1994a); Shiavi, Zhang, Limbird, and Edmondstone (1992),
described a normal pattern of muscular activity prior to the analysis of the experimental
population.

A typical kinematic gait analysis was synchronized with EMG data of the lower
leg muscles. Fine wire electrodes were used to test the vastus lateralis, vastus medialis
oblique, rectus femoris, semimembranosus, biceps femoris, tibialis anterior,
gastrocnemius, and soleus. Subjects were asked to performed seven different everyday
activities. Onset time of contraction and peak activity were described for each of the
muscles studied. Differences in muscle activities were explained, as they related to the
specific demands of the task (Ciccotti, et al., 1994a). Only the results of the walking
portion of the study will be discussed in this review. Knee extension, thigh deceleration,
and knee hyperextension prevention were all controlled by the combined action of the
hamstrings and quadriceps during the terminal part of the swing phase. The quadriceps
contracted only during the latter portion of knee extension, since the initial movement of
the swing phase is passive. The onset of hamstrings contraction occurred earlier than the
quadriceps contraction during the gait cycle. During the terminal part of the swing phase,
the tibialis anterior caused the foot to dorsiflexe in order to clear the ground. Basmajian
and Deluca (1985) described the muscular activity of the quadriceps and hamstrings as

they are synchronized with the gait phases. The quadriceps continued to contract through

26

the contact and midstance phases, as the knee is flexed and extended again. To overcome
a tendency to flex the knee during the passive lift off phase, the quadriceps increase in
activity. The hamstrings group also contracts during the passive lift off phase, to
facilitate the translation of the body over the support leg.

The results of this first study were used by Ciccotti et al. (1994b) as a control
group for the second part, in which the subjects participating in the analysis had an ACL
deficiency or had undergone ACL reconstruction. Two groups were formed for the study,
the first group underwent rehabilitation after the injury, without any surgical
intervention; and the second group underwent reconstruction of the joint and
rehabilitation afier the reconstruction. Results of this study showed that the rehabilitation
only group experienced an increase in muscular activity of the vastus lateralis. The
increased activity of the vastus lateralis was in response to a protective mechanism to
reduce the internal rotation of the tibia, which can be accentuated due to the ACL injury.
During the passive lift off phase, the rehabilitation only group, had greater activity in the
rectus femoris. The increase of activity of the rectus femoris was a result of a lesser
degree of knee flexion attempting to reduce the stress caused by anterior shear forces. In
the contact phase of the gait cycle, the first group demonstrated an increase in hamstrings
activity. This increase in hamstrings activity is a mechanism to prevent anterior
translation of the tibia caused by the contraction of the quadriceps. The longer extension
period of the knee during the stance phase acted to prevent the anterior shear of the tibia
caused by knee flexion. Greater activity of the soleus is present as a result of a longer

extension period of the knee joint. The authors concluded that the differences in muscle

27
activity were most significant in the group that had had rehabilitation only. This

conclusion was reached since the EMG profiles of the group that had reconstruction and
rehabilitation of the knee joint were similar to the normal population profiles.

With an injured ACL, a contraction of the quadriceps during a position of full
extension of the knee would produce an anterior tibial displacement over the femur
(Andriacchi, 1993). The anterior tibial translation as a result of an injury to the anterior
- cruciate ligament was studied by Yack, Riley and Whieldon (1994). The authors tested
weight bearing and nonweight bearing isometric exercises, to determine the amount of
anterior tibial translation at a 20 degree angle of knee flexion, and at three different force
levels. At 50, 75, and 100 percent of body weight, the nonweight bearing exercises
demonstrated a greater translation than weight bearing exercises. During the gait cycle,
the only time the knee reached an angle of 20 degrees was during the contact phase as it
flexed after heel strike (V almassy, 1995). With a deficient ACL, the anterior tibial
translation is limited by secondary structures. In the nonweight bearing conditions, the
strain is applied to the primary and secondary structures that control tibial translation. In
the case of an injured ACL, the hamstrings control the tibial translation. This increased
activity in the hamstrings group was evident in the contact phase, as observed by Ciccotti
et al. (1994b). In the study performed by Yack et al. (1994), the hamstrings activity was
maintained at less than 10% of its maximum. This restriction in the hamstrings activity
allowed the anterior tibial translation to be measured, as it was not being restricted by

primary or secondary structures.

28
Shiavi et al. (1992), employed the method of pattern analysis to determine the

differences in muscular activity between two groups of subjects: those with knee injuries
and a control group. Electromyography and foot switches were used to determine the
temporal variables in the gait cycle. The data from the subjects were combined into
clusters as they demonstrated similarities in muscular activity. A template was developed
to identify the normal pattern of activity for each muscle studied. The greater number of
atypical patterns were found among the injured population. The templates developed
from the data of the rectus femoris, vastus lateralis, and vastus medialis, demonstrated a
biphasic pattern. For the uninjured group, both the vastus lateralis and vastus medialis
had a stronger second phase of activity. Within the injured population, the quadricep
muscles lacked a second phase of activity during the end of the stance phase. For this
same group, a decrease in magnitude was experienced in the activity of the rectus femoris
and vastus lateralis during the contact phase. The injured group also experienced less
activity associated with the hamstrings during single leg support. A delay in the onset of
activity of the biceps femoris and semitendinosus from the end of the swing phase to the
beginning of the stance phase was observed, as well as irregularities in the activity
pattern of both muscles. The deviations experienced from the typical pattern by the
injured group, were usually characterized by less muscular activity, delay in onset time,
and less intense activity during the gait cycle phases.

The analysis of muscular activity done by Shiavi et a1. (1992) provided an
understanding of how muscles behave during different phases of the gait cycle. With this

information in mind, it is important to review how muscular contractions affect the ACL

29
throughout the range of motion. The ACL undergoes significant stress as a result of

quadriceps and hamstrings contraction during parts of the flexion-extension range
(Renstrom, Arms, Stanwyck, Johnson, and Pope, 1986). The stress applied to the ACL is
of particular interest in the rehabilitation phase that takes place after the repair of the
ligament. A simultaneous contraction of the flexor and extensor muscle groups may
reduce the stress on the ligament (O’Connor, 1993). In an effort to identify the safe zones
in which muscle contraction would not put excessive strain on the ACL (Aune,
Nordsletten, Skjeldal, Madsen, and Ekeland, 1995; Draganich, Jaeger, and Kralj, 1989), a
combination of agonist and antagonist muscle groups have been studied. In addition,
flexion angle is of great importance to the load of the ligament due to the biomechanical
advantage in the contraction of specific muscles.

To measure the strain transmitted to the ACL by muscle contraction, a strain
transducer was attached to the ACL of cadaver specimens and the joint was left to move
freely in response to the load applied to the muscle. Renstrom et al. (1986) tested the
effect of quadriceps contraction, hamstrings contraction, and simultaneous contraction of
both groups. The testing protocol consisted of isometric contractions at 15 degree
intervals from full extension to 120 degrees of flexion. The load of the hamstrings was
set at 250 N, and the load of the quadriceps was set at 400 N. For the simultaneous
contraction test, the quadriceps were set to be in equilibrium with 250 N of load applied
to the hamstrings. The results of the study showed the lower strain level range, at a
passive state, between 30 and 40 degrees of flexion; with the highest levels found at 105

to 120 degrees, full extension was shown by 0 degrees of flexion. During the quadriceps

30

contraction, the ACL strain was increased 5 % over the passive normal, between 0 and
45 degrees of flexion. Quadriceps contraction decreased the strain on the ACL when the
joint position exceeded 75 degrees of flexion. The only significant difference found
during the hamstrings contraction, was a lower strain on the ACL produced between the
angles of 75 to 105 degrees. A simultaneous contraction produced a higher strain
between full extension and 50 degrees of flexion. Simultaneous contraction of the
quadriceps and hamstrings becomes a factor during the first 20 percent of the gait cycle,
as well as for a short period before and after toe off. Over 50 degrees of flexion, the
strain decreased below the passive normal, with a significant difference found at 90 to
120 degrees of flexion. A synergistic contraction of the quadriceps and hamstrings
muscles significantly reduced the strain produced by the quadriceps alone by an average
of 2 %, with knee flexion ocurring over 30 degrees.

Similar results were found by O’Connor (1993), as he tested the effects of
cocontraction of ACL loading. A knee model was develop to facilitate the analysis for
the study. When the extensor and flexor muscles contract simultaneously, the joint does
not move. However, the muscle forces applied are not necessarily equal and opposite,
which implies that the difference has to be made up by ligament forces. Ifthe resultant
muscle force acts forward in relation to the tibia, the ACL is placed in tension, and if the
resultant force pulls back, the posterior ligament will balance the pull. O’Connor (1993)
identified the 22 degree angle of flexion as the critical angle at which the two muscle
forces are balanced without any ligament intervention. A simultaneous contraction of the

quadriceps and gastrocnemius produces a forward pull, which puts the ACL in tension.

3 l
The addition of hamstrings contraction to the contraction of the quadriceps and

gastrocnemius unloads the ACL and PCL, especially beyond the critical flexion angle.

Renstrom et al. (1986) concluded that simultaneous contraction of the quadriceps
and the hamstrings reduced the load on the ACL. However, the question remained as to
the occurrence of simultaneous contraction during flexion and extension. The existence
of coactivation of the hamstrings and quadriceps was tested using electromyography. The
researchers found that a cocontraction existed between the flexor and extensor groups
(Draganich et al., 1989). In agreement with previous studies (Renstrom et al., 1986;
O’Connor, 1993 ), it was shown that the cocontraction of the hamstrings and quadriceps
groups reduced the strain on the anterior cruciate ligament and stabilized the knee.

The analysis of muscle activation during different activities gives an indication
of synergistic action of muscles during different conditions (McNair and Wood, 1993).
In the case of an injured ACL, the cocontraction and antagonistic actions of specific
muscles become critical to the understanding of functional stability in the knee joint. The
comparison of injured and uninjured ACL’s and how the muscle function changes was
studied by Solomonow, Baratta, Zhou, Shoji, Bose, Beck and D’Ambrosia (1987), as
they investigated the stability component of the joint during flexion and extension
exercises. Surface electrodes were used to measure the activity of the quadriceps and
hamstrings during maximum voluntary contractions. The pattern found in the ACL
deficient group, demonstrated the occurrence of subluxation at about 46 degrees of
flexion. This subluxation could be seen by the temporary failure in the torque curve, and

the decrease in quadriceps activity which was accompanied by an increase in hamstrings

32

activity. This pattern was observed in most of the patients who did not have any post
injury muscle rehabilitation. The authors concluded that muscular strength contributed to
the stabilization of the knee joint. The importance of muscular strength could be
explained in that two of the patients who had maintained a high level of physical activity
after the injury, did not demonstrate a torque failure, but exhibited the same EMG
patterns as the injured group.

Contraction of the quadriceps produces an anterior displacement and rotation of
the tibia which results in subluxation of the knee joint when the ACL is not able to
stabilize the joint (Hirokawa, Solomonow, Lu, Lou, and D’Ambrosia, 1992). The stress
transmitted to the ACL by quadriceps contraction depends on the angle of knee flexion
. (Draganich et al., 1989). A load by the quadriceps between full extension and 80 degrees
of flexion produced a significant anterior displacement of the tibia. As the angle of
flexion exceeded 80 degrees, the displacement became posterior. The maximum anterior
displacement was observed at 30 degrees of flexion. The posterior tibial displacement
reflected a minimal strain to the ACL during flexion angles of 80 to 120 degrees

(Hirokawa et al., 1992). Similar conclusions were reached by Renstrom et a1. (1986).

III. MUSCLE FATIGUE

To this point, the importance of muscular activity in the role of knee stabilization
has been explained in relation to injured and uninjured conditions. One factor that can
affect the ability of the muscle to stabilize the knee, in the absence of the ACL, is muscle

fatigue. Muscle fatigue has neither been studied in relation to injury, nor how it may

33
further aflect the functionality of the knee joint. Gerdle and Karlsson (1994), conducted a

study to find the relationship between torque levels and the perception of fatigue, and the
mean frequency of the extensors of the knee. The test consisted of contraction of the knee
extensors at 70%, 25% and 10% of each individual’s maximum voluntary contraction.
The subjects were instructed to perform the contractions until exhaustion. A rating scale
was used to determine the level of muscle fatigue, as it was perceived by the subject. A
negative correlation was found between endurance time and torque. The mean frequency
of the vastus lateralis and rectus femoris decreased at a greater rate than the vastus
medialis with increasing torque levels throughout the endurance time. After the analysis
of the results, Gerdle et a1. (1994) concluded that mean frequency values were not
adequate to determine peripheral fatigue, when working with low torque levels. The
detection of muscle fatigue can be a very complicated task, as many factors influence its
onset.

Muscle fatigue is believed to be controlled and reduced during learned endurance
activities. Repetitive contractions are required to sustain an endurance activity for long
periods of time. However, the neuromuscular system reduces the load on the muscles by
sharing contraction time with different muscles to delay the onset of fatigue by any single
muscle. This sharing of contraction time is true for endurance activities in which
relatively slow and sustain contractions take place. Dul, Johnson, Shiavi, and Townsend
(1984) defined fatigue as “a continuous process during muscular contractions that
culminates in failure to maintain the required mechanical output” (p. 676). As muscle

force requirements increase, the endurance time of the muscle contractions decrease.

34
During muscular load sharing, the fiber type composition plays an important role.

Muscles with slow twitch fiber dominance generate more force during the synergistic
muscle action, delaying fatigue (Dul et al., 1984). i

The information presented in this chapter can be categorized by its relevance to
the main topic. Understanding the range of normal characteristics of gait is the first
crucial issue. With this basic information, the adaptations due to the anterior cruciate
ligament injury can be recognized. A comprehensive examination of cinematographical
data, as well as data derived from the use of electromyographic analyses, were necessary
to develop a more complete understanding of the subject. The topic of fatigue was
introduced, but information which relates to the current study is limited. Due to the lack
of understanding of the phenomenon of muscle fatigue by those in the field, as well as its
complexity, muscular fatigue has not been widely studied. Due to an injury to the ACL,
the muscles of the lower extremity become responsible for joint stabilization. Muscle
fatigue can limit the ability to fully stabilize the joint. The combined limitations of the
ACL and of the muscles of the lower extremity under a fatigued state may lead to
adaptations in the gait pattern. A set of hypotheses were formulated based on results of
studies mentioned in this chapter:

Hypothesis 1: individuals with ACL reconstruction will exhibit increased

muscular activity during the stance phase of the gait cycle, when compared with

the control group.

35
Hypothesis 2: under a fatigued state, individuals with ACL reconstruction will

have lower angular and linear displacements, velocities and accelerations
occurring at the knee joint.

Hypothesis 3: subjects with ACL reconstruction will experience adaptations of
greater magnitudes at the knee joint under the fatigued state when compared to

the control group.

CHAPTER III

METHODS

The purpose of this study was to perform a three dimensional kinematic analysis
utilizing EMG in order to examine the effects of muscle fatigue on gait characteristics of
individuals with a reconstructed anterior cruciate ligament, compared to uninjured
individuals. Subjects were tested under unfatigued and fatigued conditions. The muscles

of the lower extremity were fatigued utilizing a submaximal bicycle ergometer test.

I. SUBJECTS

Four male and one female volunteers (mean age of 26.6 years) took part in the
study. All subjects were involved in physical activity at the recreational level, at least
once a week, at the time of the study. Subject’s activity level was taken into
consideration during the selection process. Similar levels of activity among subjects were
preferred, to reduce variability within groups. Two subjects were part of the treatment
(ACL injured) group, while three subjects were in the control (non injured) group.
Selection of the injured subjects was based on the following prerequisites: (1) a
diagnosed isolated injury of the anterior cruciate ligament, (2) similar ACL

reconstructions within 15 months prior to the study’s testing date (3) similar strength test

36

37
results in each knee, and (4) subjects demonstrating results of laxity tests within the

normal range (+/- 1 on the Lachman’s scale) in the non injured extremity. Subjects in the
treatment group were tested for leg strength in both legs prior to the acceptance into the
study. Leg strength was tested using a Cybex H dynamometer, to determine the percent
of strength recovery as compared with the contralateral leg. A right vs. left strength
percentage greater than 15 would excuse the subject from the study. Subjects with no
previous history of lower extremity injuries formed the control group. Laxity was tested
using the Lachman test, which was performed by a certified athletic trainer. The laxity
test was performed on the control group to assure normal range (+/- 1 on the Lachman
test) in both knees. All subjects were required to sign an informed consent form (see
Appendix A1) and complete a personal data sheet (see Appendix E) prior to their
participation in the study. Subjects being considered for the ACL group signed an
additional informed consent form (see Appendix A2) to allow strength test screening
prior to the actual kinematic data analysis.

Anthropometric measurements were taken by the investigator prior to the first
trial, the protocol followed guidelines by Lohman, Roche, and Martorell (1988). These
measurements allowed for a quantitative description of the segments of the lower
extremity and to check for asymmetries of leg segments. The measurements consisted of
weight, standing height, leg length, upper thigh girth, calf girth, and femur breadth;
measurements were taken from both right and left sides (see Appendix B). The subjects
was asked to identify their dominant side defined as their preferred kicking leg. The

subjects were marked with spherical reflective joint markers to facilitate the

38

identification of the joint during the digitization process. Subjects were asked to wear
tight fitting dark shorts to allow for a better contrast of the markers. The joints were first
marked with water resistant ink markers, to allow for consistant placement of reflective
joint markers in case they fell off. Markers were placed over the following bony
landmarks on the injured limb: fifth metatarsal, calcaneus, lateral malleolus, lateral
femoral epicondyle, greater trochanter, and anterior superior illiac spine (ASIS). For the
uninjured side, markers were placed over the fifth metatarsal, calcaneus, medial
malleolus, and medial femoral epicondyle. The marked joints were used for the input of
position data for analysis of displacement, and calculation and analysis of velocity and
acceleration parameters.

Subject preparation for electromyographic data collection consisted of shaving
the area over the belly of the biceps femoris and the rectus femoris muscles, cleaning and
slightly abrading the skin with a dry wash cloth to reduce resistance to signal uptake. A
water based gel was applied to the electrodes to reduce electrical resistance.
Hypoallergenic tape was used to adhere the electrodes to the skin. Electromyographic
data were collected during all trials, as well as during the fatiguing period.

Each subject was asked to complete three successful trials of walking in both the
unfatigued and fatigued states. A trial was considered successful when a complete stance
phase of the injured side was within the confmements of the calibrated space. Walking
under the unfatigued condition was filmed first, followed by a procedure to induce
muscle fatigue. The subjects were then filmed while under a fatigued state. Subjects were

given three practice trials in the filming area prior to the initiation of testing. Subjects

39
were asked to walk at what they considered a normal, comfortable speed. All subjects

walked with the injured side closer to the cameras, while subjects in the control group
walked with their right side closer to the cameras. During the practice trials, the
researcher observed if the stance phase occured in the calibrated space. The starting point
was marked for each subject, to allow consistency in obtaining the stance phase in the
center of the calibrated space. Subjects performed all trials barefooted, to allow for
natural movements of the joints during walking.

After the subjects had completed the first three trials, they proceeded to the
second phase of the test: fatigue of the lower extremity muscles. To reach a fatigued
state, the subjects rode a bicycle ergometer. The resistance was increased every two
minutes following the protocol for the submaximal bicycle ergometer test, until the onset
of fatigue (see Appendix C for complete protocol). The subjects were asked to rate their
perceived muscular fatigue every two minutes prior to the increase in work load. Muscle
fatigue was determined by each subject’s rating of perceived exertion (RPE). A rating of
8 on Borg’s 10 point RPE scale indicated a fatigued state, and the conclusion of the
fatiguing process. In conjunction with the Borg scale, electromyographic signals were
used to aid in the detection of fatigue. When the integrated EMG signal demonstrated an
increase of ZOO-300% in activity level, muscle fatigue was assumed. After the detection
of fatigue by either the perceived exertion scale or electromyographic data, the subjects
repeated the three gait collection trials, following the same protocol as was described
earlier. After the completion of each trial, the subjects were asked to rate their perceived

muscular fatigue. If their rating of perceived exertion dropped more than two points they

40
were asked to ride on the bicycle ergometer starting at the workload at which fatigue was

previously detected.

11. DATA COLLECTION PROCEDURES

Testing took place in the Intramural (1M) Sports Circle, at Michigan State
University. Instrumentation and equipment were owned by the Department of Physical
Education and Exercise Science. Surface electrodes were borrowed from the University
of Missouri. Two S-VHS video cameras were used to film the subjects as they walked
along a five meter walkway. The cameras were placed at a 60 degree angle to each other,
allowing the best view of all markers as the subjects moved in the sagittal plane along the
field of view (see Figure 4). The cameras filmed at a speed of 60 frames per second and
the shutter speed was set at 1/3 00 second. Prior to subject filming, a calibration structure
was filmed to define the volume over the walkway. The calibration structure consisted of
16 control points, four points at each corner of the rectangular volume. The structure
defined a volume of 3 meters long by 1 meter wide by 1.125 meters high. The four
corners defining the volume had a symmetrical point distribution; these points were
placed at 13.5 centimeters, 47.25 centimeters, 81 centimeters, and 112.5 centimeters

from the floor (see Figure 5).

41

 

 

 

 

 

Figure 4: Testing Setup

.................................................

1.125 meters

 

 

 

 

Figure 5: Calibration Structure

Timing lights were placed in the field of view of both cameras to allow
synchronization of frames during data reduction. A line was drawn perpendicular to the
walkway and EMG data collection was initiated manually as the subject crossed the line.
These procedures allowed EMG data to be matched with the kinematic values during
data analysis. Surface electrodes were placed over the belly of the rectus femoris and
biceps femoris of the injured limb and the leg closest to the cameras of subjects in the

control group. The surface electrodes transmited the muscles’ signals directly to the

42
analog module of the Ariel Performance Analysis System. Electromyographic data were

recorded for three seconds during each trial of gait analysis. During the fatiguing process,
EMG signals were recorded every two minutes to monitor muscular activity, prior to
each increase of resistance, for a period of three seconds. The investigator read the
electromyographic data, if a ZOO-300% increase in the integrated EMG signal was

observed and the subject indicated a rating of 8 on the RPE scale, fatigue was assumed.

IH. DATA REDUCTION PROCEDURES

The film data from both cameras was analyzed using the Ariel Performance
Analysis System (APAS). The calibrated volume was defined following APAS’s
requirements, refer to Angeli (1995) (see Appendix D). For the purpose of error
reduction, the same fixed point was used for all trials and the first digitized calibration
structure frame was used for all trials. In the case of subjects with injuries to the left
knee, the calibration coefficients needed to be rotated due to a limitation in the APAS
analysis software. APAS software does not allow the changes to be made post
digitization. This rotation allowed for the (0,0,0) point in the coordinate system to be the
same for all subjects, as they walked in a positive direction according to the defined X
axis. This procedure was used to facilitate the comparison of results.

All trials were previewed prior to the initiation of the analysis. The best two trials
for each subject under each condition were analyzed. The best trials were selected on the

basis of visibility of the markers and location of full stance within the calibrated volume.

43

Under the grabbing module of the APAS system, the parameters were set to grab frame,

starting ten frames prior to heelstrike of the injured limb, through the complete cycle, and

ending ten frames following the heelstrike marking the completion of the cycle. The

order of joint digitization was the same for all subjects whose right side was closer to the

camera: right toe, right heel, right ankle, right knee, right hip, lefi toe, left heel, left

ankle, left knee, left hip, and A818 (see Figure 6). For subjects whose left side was closer

to the cameras, the process started on the left leg, followed by the right leg and A818.

The transforming module (utilizing the direct linear transformation procedure) combined

the two digitized views into three dimensional. The cubic spline technique was used to

smooth the data.

Right

Figure 6: Digitization Order

IV. DATA ANALYSIS

 

}

 

7

10

6

Left

The two best trials for each subject were included in the data analysis. The trials

were chosen based on location of the stance phase in the calibrated volume, and the

44

ability to see all the joint markers throughout most of the gait cycle. Linear and angular
displacements, velocities and accelerations were calculated and analyzed for each joint
digitized. Electromyographic data were synchronized with kinematic data, using
temporal parameters, for completion of the analysis. Results were compared between the
unfatigued and fatigued conditions for both the injured and uninjured groups. A
quantitative description was performed to highlight differences observed within one
group under the two different conditions. These observed differences were then
compared against the other group. A descriptive analysis best served the purposes of the
study, as the adaptations may not be significant to be detected through statistical analyses

or the data collection system (APAS).

CHAPTER IV

RESULTS AND DISCUSSION

The results of the three dimensional gait analysis consisted of a comparison of
linear and angular parameters under unfatigued and fatigued conditions. Linear and
angular displacements, velocities, and accelerations were calculated for three control
subjects, and two subjects with ACL reconstruction. Electromyographic (EMG) data
were used to determine muscular activity patterns for the quadriceps and hamstrings
muscle groups during the walk.

All the data were normalized to percent gait cycle. Angular parameters were
expressed as the rotation of the distal segment relative to the proximal segment. Linear
and angular parameters were calculated for the side closer to the camera. Angular
analysis of the data were presented for sagittal and frontal planes of motion; rotations
about the X and Z axes, respectively.

EMG data were analyzed under the unfatigued and fatigued conditions to
determine muscle activity characteristics. EMG data were collected for the involved side
in subjects of the ACL reconstructed group and on the primarily targeted side for the
subjects in the control group. The EMG signal was full wave rectified, and filtered using

a 0.3 sec window envelop. The data were synchronized with the kinematic parameters to

45

46

determine muscular activity throughout the complete gait cycle. Synchronization was
performed by identifying foot contact for both EMG and kinematic data. All the signals
were amplified and filtered under the same conditions. EMG data for Subject 1 of the
control group and Subject 5 of the injured group were not included in the description due
to equipment failure during data collection.

The data analysis consisted of a general description of gait patterns observed
during two trials for both tested conditions. The results are grouped in two main parts.
First, results from angular parameters and muscular activity data for the control group
under both unfatigued and fatigued conditions are presented, followed by angular
parameters and muscular activity data for the treatment group under these same
conditions. A description of normal angular characteristics will precede the report of the
results obtained in the study. Secondly, results of linear parameters for the control
group under unfatigued and fatigued states, followed by the results of linear parameters
for the treatment group under both tested conditions are presented. Normal linear data are

presented prior to the results of this study for the control and treatment groups.

1. AN GULAR MOTION
A. Normal Angular Displacement Data

In gait analysis, the concept of normal data needs to be carefully examined. For
the purpose of this paper, normal data were identified as a general pattern which was
representative of healthy individuals in the “average” population. A note should be made

pertaining the definition of normal data: normal data should be inclusive of all the

47
patterns observed in individuals with no history of pathological conditions which might

cause adaptations in their gait patterns. Because of the wide range of gait characteristics
observed within the “normal” population, the trend is to use the average pattern as
“normal”. Deviations outside the “normal” pattern may or may not be an indication of
pathological conditions affecting the individual’s gait.

Angular displacements for the knee joint were presented for flexion/extension and
abduction/adduction data. Researchers have shown that a normal flexion/extension
angular displacement curve presents two defined periods (V almassy, 1995). At foot
contact the knee is in full extension. Knee flexion of 2 to 3 degrees at foot contact is also
considered normal. During the initial 20% of the gait cycle the knee flexes to
approximately 15 degrees. This period is normally referred as the initial flexion period.
Knee flexion acts to absorb shock and decelerate the body following foot contact. During
midstance, from 20% to 40% of the gait cycle, the knee extends and returns to the
position of full extension presented at foot contact. Knee extension assists in the forward
propulsion of the body as the trunk is carried over the supporting leg. Knee extension
continues from midstance into the active propulsion phase. A second and larger
flexion/extension period is presented during the swing phase of the gait cycle. The knee
initiates the second period of flexion in preparation for the swing phase. At toe off, the
knee is flexed approximately 40 degrees. Knee flexion increases throughout the swing
phase to provide toe clearance during advancement of the leg. Maximum flexion is

reached at about 80% of the gait cycle (midswing), reaching approximately 60 degrees.

48
When the ankle joint has moved forward of the hip joint, the knee starts its second

extension period in preparation for foot contact. (See Figure 7).

 

  
 
   

 

 

 

 

 

 

Knee Flexion/Extension Angular
Displacement
60 _-
E 50 dr-
5
m 33 40 -s Toe off
8 E-
- er 30 1r-
§ ‘5
“g 20 4e Midstance
8
“:5 10 .FC F0
% Gait Cycle
0 r . a 4 .
0% 20% 40% 60% 80% 100%
t SthIme > Swrnglee

 

Figure 7: Knee Flexion/Extension Angular Displacement. Normal Pattern.

The normal abduction/adduction movement patterns for angular knee
displacement exhibit smaller magnitudes when compared to the flexion/extension
patterns. The leg is involved mainly with flexion and extension as it moves primarily in
the sagittal plane. Therefore, the knee presents greater displacements for
flexion/extension than abduction/adduction. Angular knee displacements along the
frontal plane are also harder to detect, because of the smaller ranges of motion. The

neutral position was defined as 0 degrees of abduction, representing a perfect alignment

49
of the femoral condyles over the tibial condyles. At foot contact the knee is in neutral

position. Throughout the stance phase, the knee maintains this initial position, presenting
only small fluctuations in the abduction/adduction displacement of the joint. These
fluctuations range approximately 2 degrees in either an abduction or an adduction
direction. At the initiation of the swing phase, the knee adducts to approximately 5
degrees, and then enters into an abduction period reaching maximum abduction of 5
degrees. During the terminal 10% of the gait cycle, adduction at the knee is performed to

return the joint to neutral position at foot contact. (See Figure 8).

 

 

 

 

Knee AbductionIAdduction Angular
Displacement
25 -.
20 -.
.. 15 ..
a
g 3 10 4-
h <
32?: 5“ M‘Ilnce Toast!
0 6 AC
a FC
01% Wm 60% 80% 100%
'5 " It Gait cycle
-10 .-

 

 

Figure 8: Knee Abduction/Adduction Angular Displacement. Normal Pattern.

Several authors have defined normal muscular activity patterns during gait
(Basmajian et al., 1985; Ciccotti et al., 1994). Muscular activity during gait can be
analyzed by targeting different muscles of the lower extremity. The muscles usually
targeted for EMG data collection include: the rectus femoris, vastus lateralis, biceps

femoris, semimembranosis, gastrocnemious, and tibialis anterior. For the purpose of this

50

study, the rectus femoris and vastus lateralis will be combined and identified as the
quadriceps group. The biceps femoris and semitendinosis will be identified as the
hamstrings group. The gastrocnemious and tibialis anterior will not be included in the
discussion. A normal EMG pattern of the quadriceps and hamstrings during a complete
gait cycle is shown in Figure 9. Under normal conditions the quadriceps are active at foot
contact and act to control knee flexion through eccentric contraction during the initial
20% of the gait cycle. The hamstrings group are also active at foot contact to
approximately 15% of the gait cycle. Hamstrings contraction during the initial portion of
the stance phase prevents hyperextension at the knee joint. The quadriceps group remains
active during the initial portion of the knee extension phase. Quadriceps activity
decreases after the initial 25% of the gait cycle. A second quadriceps contraction phase is
observed from 50% to 60% of the gait cycle. During the passive lift off phase, the
quadriceps act to flex the hip joint and to restrict excessive flexion at the knee joint.
During this period, the rectus femoris is the only active muscle of the quadriceps group,
since it is the only muscle of the quadriceps group that crosses the hip joint. At 7 5% of
the gait cycle, the hamstrings contract to assist in knee flexion during the swing phase.
The hamstrings remain active until the completion of the gait cycle. After midswing the
hamstrings contract to control hip flexion as the limb is prepared for foot contact. During
the later portion of the swing phase, the hamstrings again act to prevent hyperextension
of the knee joint. The quadriceps contract during the last 5% of the gait cycle to assist in

knee extension and hip flexion in preparation for second foot contact.

51

 

EMG Recordings for Normal Walking

 

 

a Quads
. Hams

 

 

 

 

 

 

Figure 9: Muscular Activity Patterns for the Quadriceps and Hamstrings Muscle Groups.
Normal Data.

Prior to filming, anthropometric measurements were taken of all subjects. No
asymmetries were found in the leg segment lengths when anthropometric measurements
were compared bilaterally for each subject in the study. In addition, subjects in the ACL
reconstruction group were screened, prior to inclusion in the study, for leg strength using
a CYBEX Dynamometer. The accepted three to two ratio, of the hamstrings to
quadriceps muscle strength, was found in the reconstructed group. In addition, strength
differences lower than 15 percent between left and right sides for both quadriceps and
hamstrings groups were found. This strength recovery rate of the injured side of more
than 85 percent when compared to the contralateral side strength value, is accepted by the
National Athletic Training Association (NATA) as the minimal recovery percentage for
reintegration of the athlete into practice. Finally, the Lachman’s knee laxity test was

given to subjects in both groups by a Certified Athletic Trainer. The results of this test

52
were that all subjects in both the control group and the ACL reconstruction group had a

range in the Lachman’s test of +/- 1, which indicated “stable knees”.

B. Control Group

The angular displacement data of the control group were compared to the norms
already presented. The data for the unfatigued condition were presented first and a
second comparison was made between the data for the fatigued condition and the
unfatigued condition. The graph representing the data obtained during the trials are
presented in Appendix F, only a representative graph of the common pattern presented by
the control group was discussed in this section. Under the unfatigued condition the
control group demonstrated the characteristic flexion/extension pattern exhibited during
normal gait, see Figure 10. However, none of the subjects experienced full extension at
the knee joint during foot contact. The knee joint was flexed approximately 12 degrees at
foot contact. This flexion angle was correspondent to full extension of the joint. The
range of initial flexion was 15 degrees for both the control and normal groups. The initial
flexion period occurred during the first 20% of the gait cycle. The control group, did not
demonstrate full extension at the knee joint during midstance. However, the knee joint
was extended to the initial 12 degrees of flexion, demonstrating a normal
flexion/extension pattern during the stance phase. Subject 2 (CLM2) presented restricted
knee extension during midstance, only extending to 18 degrees. The extension period
was completed at 40% of the gait cycle for all subjects. During the swing phase

maximum flexion of 65-75 degrees was observed at the knee joint. Second foot contact

53

occurred with 12 degrees of flexion at the knee joint, demonstrating consistency and

agreement in the amount of flexion presented at foot contact.

 

 

 

 

 

 

 

 

 

Knee FIexionlExtension Angular
8° 1' Displacement
70 “ CL _,
E
E
X
3 s:
2 Le.
§ .5
In
I:
s
K
In
0% 20% 40% 50% 80% 100%

 

 

 

Figure 10: Knee Flexion/Extension Angular Displacement under the Unfatigued
Condition. Control Group.

All the subjects in the control group presented the same knee angular velocity
pattern. Figure 11 represents the angular velocity graph characteristics of the control
group under the unfatigued condition. The knee angular velocity presented a negative
slope for the initial 10% of the gait cycle. The angular velocity returned to 0
degrees/second at the conclusion of the knee flexion period. A positive slope of
approximately the same magnitude as the previous period was observed between 20%
and 30% of the cycle. An opposing negative slope in the velocity curve was observed
from 30% to 41% of the cycle. This pattern was observed during the knee extension
period. The velocity magnitudes presented during the flexion period were equal to those
presented during the extension phase. A negative slope in the velocity curve was

observed from 41% to 60% of the gait cycle. This decrease in velocity demonstrated a

54
magnitude of approximately 250 degrees/second. Following toe off, the velocity at the

knee joint increased until 90% of the gait cycle. During the last 10% of the gait cycle a

negative slope was observed in knee velocity as the limb slowed down in preparation for

 

 

 

foot contact.

400 Knee Flexion/Extension Angular Velocity

300 .

200 ll
'0
E Midstance
§ 100 n
? 0 PC A PC
a . a 4 i t
a 0116 40% 60% 80% 100%

-100 w

-200 ,. Toe cit

% Gait Cycle
.300 .L

 

 

 

Figure 11: Knee Flexion/Extension Angular Velocity under the Unfatigued Condition.
Control Group.

The angular acceleration pattern of the knee joint exhibited by the control group
under the unfatigued condition is presented in Figure 12. At foot contact, the knee had
reached an acceleration magnitude of -2000 degrees/second? An acceleration period was
initiated at the knee joint to approximately 20% of the cycle. A deceleration period was
observed from 20% to 50% of the gait cycle, corresponding to extension at the knee joint
and the initiation of the second flexion period presented during late stance phase. A
second larger acceleration period was presented from 50% to 80% of the gait cycle, as
the leg moved forward in the swing phase. Past midswing, the knee joint movement

decelerated for the purpose of foot contact, reaching the lowest acceleration magnitude

prior to the completion of the gait cycle.

55

 

 

 

Knee Flexion/Extension Angular

400° " Acceleration

3000 ..

2000 ..

Midstue

E 1“” . Toe of
g /\
fi 0 i 1 1 4. 1
§ 096 20% ‘16 80% 100%
gt -1000 ..
n

.2000 .

F0 FC
3000 ..
°/.oaitqtele
4000 ..

 

 

 

Figure 12: Knee Flexion/Extension Angular Acceleration under the Unfatigued
Condition. Control Group.

Differences in the abduction/adduction angular displacements were found across
subjects in the control group. Data for both Subjects 1 (CLMl) and 3 (CLF3) are
presented in Figure 13, as these two subjects defined the extremes of the control group.
At foot contact the knee joint was adducted approximately 2 degrees for all the control
group subjects. For the initial 40% of the gait cycle, the knee maintained the adducted
position by either further adducting, or abducting and adducting through a range of 2
degrees from the initial position. Differences between subjects were present during the
last 60% of the gait cycle. Knee abduction was observed in all control subjects at 40% of
the gait cycle. The magnitude of knee abduction varied from 20 to 7 degrees for Subjects
1 and 3, respectively. The time period in which the knee was abducting was different for
all subjects in the control group. The knee joint was observed at its most abducted

position from approximately 70 to 80% of the gait cycle, for these two subjects.

56

 

Knee Abduction/Adduction Angular
'1 Displacement

bi

 

a N
(n O
1 l
I I

 

 

 

Degrees
—L
O
1

Add.(-)IAbd.(+)
(n o m
1 9 1

 

 

 

I
_h
0
l
I

96 Gait Cycle

 

 

 

Figure 13: Knee Abduction/Adduction Angular Displacement under the Unfatigued
Condition. Control Group.

Due to the differences observed between subjects on the abduction/adduction
angular displacements, abduction/adduction angular velocity patterns are presented for
Subjects 1 and 3, see Figure 14. Due to the fluctuation between abduction and adduction
presented by Subject 1 during the initial 40% of the cycle, the velocity graph also
exhibited various changes during this period. The angular velocity maintained a positive
magnitude during most of the knee abduction phase, from 40% to 65% of the cycle.
Negative velocity values were observed during the last portion of the swing phase, as the
knee adducted to the foot contact position. Subject 3 demonstrated fewer fluctuations in
the velocity graph for the initial 40% of the cycle. This corresponded to the adduction of
the knee experienced after foot contact. After 40% of the gait cycle Subject 3 presented
the same general velocity pattern as that presented by Subject 1. Positive angular
velocities were observed during abduction, and negative velocities were observed after

maximum abduction of the knee.

57

 

 

 

 

 

 

 

 

Knee Abduction/Adduction Angular Knee Abduction/Adductlon Angular
Velocity- Subject 1 15° -- Velocity - Subject 3
100 ..
50 Toe ofl
E 50 F0 E "F Midstance
3 :%/1|:c 3 C
$ 1 fi 0 1 a 1
: : 016% 60% so 1
550 5 50 .. F
850M1$mnw 8 c
100 100 ..
150 150 ._
SSGaIt Cycle resonant.
-200 -200 .-
(a) (b)

Figure 14: Knee Abduction/Adduction Angular Velocity under the Unfatigued

Condition. (a) Subject 1 (b) Subject 3.

The acceleration graphs corresponding to knee abduction/adduction are presented

in Figure 15. The acceleration graph exhibited by Subject 1 was indicative of the changes

in velocity presented throughout the gait cycle. Abrupt changes were displayed on the

acceleration graph describing fast and small changes in the velocity of the knee joint. The

acceleration graph for Subject 3 did not demonstrate similar magnitudes changes,

presenting a smoother curve. This subject experienced more controlled abduction and

adduction of the knee joint throughout the gait cycle.

 

Knee AbductionIAdductlon Angular
Acceleration - Subject 1

     
   
 

Dogreeslseeondz

   

Midstance Toe of!
56 Gait Cycle

 

 

‘

l

i
l
l

 

Degrees/seem

Knee Abduction/Adductlon Angular
Aweleraflon - Subject 3
2500
2000 l
1500 1
10m 1 Toe cll'

. Midstance
TFC

. [Fe
.500 0i" A

Wort 40% 60% Wwors
4on

.1500
-2000 ;
Ito-rt O’cla

canl
.3000l

 

 

(a) (b)
Figure 15: Knee Abduction/Adduction Angular Acceleration under the Unfatigued

Condition. (a) Subject 1 (b) Subject 3

 

58

The knee angular displacements for the fatigued condition representative of the
control group data are presented in Figure 16. The characteristic flexion/extension curve
was presented by all subjects under the fatigued condition. Some differences in the range
of motion were found when data were compared with the unfatigued state. The degree of
knee flexion at foot contact was found to be the same under both conditions, 12 degrees.
Initial flexion presented a range of approximately 18 degrees, peaking at 20% of the gait
cycle. Under the fatigued condition all subjects presented a greater magnitude of knee
flexion during the stance phase. Extension of the knee joint occurred over the expected
40% of the cycle. As the knee returned to the foot contact position, the slope of the
displacement graph decreased, causing a prolonged extension period of 25% of the gait
cycle. Subject 2 demonstrated limited extension of the knee joint during midstance.
However, this reduction in knee extension was consistent with the reduction observed
during the unfatigued state. An increase in maximum flexion of 5 degrees over the
unfatigued state was demonstrated in the second flexion period of the knee joint.
Maximum knee flexion was reached later in the swing phase, when compared to the
unfatigued state, due to the longer extension period presented during the stance phase. At
second foot contact, at the end of the gait cycle, the knee was flexed 12 degrees,

matching the amount of flexion presented during the initial foot contact.

59

 

Knee FlexionlExtension Angular

 

 

 

 

Degrees

Extension(-)IFlexlon (+)

 

 

 

 

 

 

Figure 16: Knee Flexion/Extension Angular Displacement under the Fatigued Condition.
Control Group.

Flexion/extension angular velocity patterns at the knee joint under the fatigued
state are presented in Figure 17. The pattern presented by these subjects under the
fatigued state compared closely to the patterns found under the unfatigued state. Due to
the increased knee flexion shown during the stance phase, the negative-positive phase in
the velocity graph occurred from foot contact to approximately 25% of the gait cycle.
The longer pattern was due to an increase in knee flexion during the stance phase of the
fatigued condition. The magnitude of the velocity was greater for the fatigued condition.
The second period presented on the velocity graph corresponded to knee extension
during midstance. Under the fatigued state, the pattern was shifted so that it occurred
later during the gait cycle. The shift was due to the longer flexion phase previously
discussed. The magnitude presented during this second phase was greater during the
fatigued state when compared to the unfatigued trials. The knee joint extended at a faster

velocity to be able to cover a greater range of motion under the same amount of time.

60

The reduction in knee velocity following knee extension was of greater magnitude under
the fatigued state than the unfatigued state. During the swing phase, the knee angular
velocity increased to about 90% of the cycle. The velocity of the knee joint reached a
greater magnitude under the fatigued state, due to the larger flexion range presented

under this state when compared with the unfatigued state.

 

Knee Flexion/Extension Angular Velocity
.. Fatigued
300 ii ..... Unhtigued

 

 

 

 

 

 

Degreeslsecond
o
-n
O
>
y

 

0 , ’, 4096‘.
-100 ‘
-200
'/. Gait Cycle
800

 

 

 

Figure 17 : Knee Flexion/Extension Angular Velocity under the Fatigued Condition.
Control Group.

The acceleration graph in Figure 18 corresponds to the velocity graph presented
for the fatigued trial. The pattern of acceleration of the knee joint under the fatigued state
closely followed the pattern presented under the unfatigued state. However, differences
in magnitudes were apparent when both conditions were compared. At foot contact,
under the fatigued state, the knee joint was decelerated to approximately -1000
degrees/secondz, while the magnitude under the unfatigued condition was almost
doubled. During the swing phase the subjects showed greater acceleration at the knee
joint under the fatigued condition than under the unfatigued condition. This was due to

greater velocity magnitudes presented under the unfatigued state during this period.

61

 

 

 

 

 

Knee Flexion/Extension Angular
3°00 ‘ Fatigued
..... Unfatigued
2000 ..

 

o
s

N

3
I

Degrees/secondz
:1 §
L . ~
>
O

 

$3.3?

[ '1. Gait Cycle

 

 

 

Figure 18: Knee Flexion/Extension Angular Acceleration under the Fatigued Condition.
Control Group.

Differences were observed in the abduction and adduction angular displacement
magnitudes, under the fatigued state. Subjects 1 and 3 were used for comparison of the
abduction/adduction angular displacement characteristics under the fatigued condition,
see Figure 19. At foot contact the knee joint was adducted 5 degrees for both subjects 1
and 3. An adducted position at the knee was maintained by abduction/adduction
movements of 2 degrees throughout the initial 35% of the gait cycle. Subject 1,
demonstrated 2 degrees adduction of the knee during the initial portion of the stance
phase. Entering in the second marked period, the knee joint abducted to 20 degrees.
Subject 3 demonstrated an abduction of 12 degrees, showing a less pronounced abduction
of the knee joint when compared to Subject 1. During the unfatigued state Subject 3 had
7 degrees of abduction. Maximum abduction occurred at approximately 60% of the gait

cycle. The largest abduction magnitude was reached earlier during the gait cycle under

62
the fatigued state. However, the time period of abduction of the knee joint was found to

be equal under both unfatigued and fatigued conditions.

 

Knee Abduction/Adduetion Angular
25 7 Displacement
CLM1

 

 

 

 

 

Degrees

Add.(-)IAbd.(+)

 

 

 

%GaitCycle

 

 

 

Figure 19: Knee Abduction/Adduction Angular Displacement under the Fatigued
Condition. Control Group.

The knee’s abduction/adduction angular velocity graphs for the fatigued state are
presented in Figure 20. Data for Subjects 1 and 3 were presented due to the differences
observed in the displacement data. Under the fatigued condition, Subject 1 demonstrated
a more controlled movement pattern when compared to Subject 3. The differences
between the two subjects observed in the velocity patterns, suggest less abrupt changes
presented by Subject 1. For the initial 35% of the gait cycle, the knee adducted, therefore
presenting a velocity graph with no abrupt changes over small periods of time. As the
knee was adducted over the initial 20% of the cycle, a negative slope is seen on the
velocity graph, due to a slower rate of change of abduction/adduction of the knee joint. A
positive abduction slope in the velocity graph was observed from 20% to approximately
60% of the cycle. During the swing phase the velocity was mainly negative until the

completion of the cycle. The velocity pattern presented by Subject 3 illustrated the fast

63
changes occurring throughout the gait cycle. Constant changes in the velocity graph were

presented for the initial 80% of the cycle. This subject presented the smallest

abduction/adduction range of motion throughout the gait cycle, which demonstrated

 

 

small velocity magnitudes.
Knee AbducflonlAdducfiOn Angular Knee AbductionIAdductIon Angus
15° 1. Velocity - subject 1 150 1- Velocity - Subject 3
A

   

-150 .. 'bOalt Gide
Walled *0." ON" __Fatigued
4!!) .l ..... Urbtiatnd ~20) .. ..... WW

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(a) (b)
Figure 20: Knee Abduction/Adduction Angular Velocity under the Fatigued Condition.

(a) Subject 1 (b) Subject 3.

Abduction/adduction angular acceleration graphs for the fatigued condition are
presented in Figure 21. The acceleration graphs correspond to the velocity graphs
described above. The acceleration pattern for Subject 1 demonstrated changes in
magnitude and direction for the initial 50% of the gait cycle. A negative acceleration
peak followed the initiation of swing, and a positive peak was experienced after
midswing. Subject 1 presented similar angular acceleration patterns fol: both unfatigued
and fatigued conditions. Differences were observed only on acceleration magnitudes.
When the acceleration graph for Subject 3 was analyzed, the pattern indicated constant
changes in velocity over small periods of time. There was no defined pattern as to the

movement of the knee joint throughout the gait cycle. Under the fatigued condition, the

64

acceleration pattern for Subject 3 resembled that of Subject 1 under the same condition.
In contrast with the smoother curve presented by Subject 3 under the unfatigued

condition.

 

 

Knee Abduction/Adductlon Angular Knee AbductionIAdducflon Angular
Acceleration - Subject 1

 

 

 

 

~25» f‘w U 450) _Fm
m ..... Urfliwed m ccccc Unfllgued

 

Midswit'o

 

 

 

 

 

 

 

 

 

 

 

 

(a) (b)
Figure 21: Knee Abduction/Adduction Angular Acceleration under the Fatigued

Condition. (a) Subject 1 (b) Subject 3.

Data collected through electromyography for the quadriceps and hamstrings
muscles groups were used to determine temporal parameters of muscular activity specific
to the two muscle groups during gait. Reference to intensity of contraction was only used
for comparison between the activity patterns presented by both muscle groups. Intensity
was not used as a measurement of the force of contraction. The muscle activity patterns
presented by Subjects 2 and 3 under the unfatigued condition differed from the normal
pattern presented earlier. In Figures 22 a and b, the normal activity patterns have been
inserted with each subject’s pattern to facilitate comparison . The activity pattern
presented by the quadriceps group was different for both subjects, however similar
activity patterns were seen for the hamstrings group for these two subjects. Subject 2

(Figure 22a) demonstrated quadriceps activity between 30% and 75% of the gait cycle.

65
This activity corresponded to the extension of the knee during midstance. This subject

did not demonstrate any quadriceps activity during the initial flexion period, where the
quadriceps are expected to eccentricity contract to control the action at the knee joint.
Subject 3 showed quadriceps activity during the initial 20% of the gait cycle and also on
the last 10% of the cycle. The quadriceps firing pattern demonstrated by this subject
more closely matched the normal EMG pattern described earlier. The quadriceps were
active to control knee flexion during the stance phase, and to extend the knee joint during
the last portion of the swing phase. Subject 2 demonstrated activity by the hamstrings
from 15% to 70% of the gait cycle, while Subject 3 showed hamstrings activity from
20% to 80% of the cycle. During this period the hamstrings acted at both the knee and
hip joints. Quadriceps contraction was of greater intensity when compared to the

hamstrings.

 

 

 

 

 

 

 

 

( (b)
Figure 22: Muscular Activity Patterns for the Quadriceps and Hamstrings Muscle Groups
under the Unfatigued Condition. (a) Subject 2 (b) Subject 3.

66
During the fatigued trials the muscle activity presented by both muscle groups

differed from the pattern demonstrated during the unfatigued condition. (See Figure 23).
Although both subjects presented different adaptations on their muscular activity
patterns, under the fatigued state, subjects demonstrated a more intense hamstrings
contraction when compared to the intensity of the contraction of the quadriceps group.
Subject 2 demonstrated quadriceps activity during the initial 20% of the cycle, and
during the last 45% of the gait cycle. Subject 3 demonstrated quadriceps activity for the
initial 40% of the gait cycle. Subject 2 demonstrated constant activity of the hamstrings
group throughout the gait cycle. While Subject 3 demonstrated hamstrings activity from

5% to 25% and the last 20% of the gait cycle.

 

 

 

 

 

 

 

 

 

Figure 23: Muscular Activity Patterns for the Quadriceps and Hamstrings Muscle Groups
under the Fatigued Condition. (a) Subject 2 (b) Subject 3.
C. ACL Reconstructed group

Both subjects (Subjects 4 and 5) forming part of the treatment group were
targeted on the left side. Figure 24 is representative of the knee angular displacements

observed for both subjects under the unfatigued condition. Differences were observed

67
between the gait characteristics exhibited by the ACL-reconstructed and control groups

under the fatigued state. At foot contact both subjects presented 10 degrees of knee
flexion. Subject 4 (ACLM4) demonstrated the characteristic 15 degrees of initial flexion
peaking at 20% of the gait cycle. Subject 5 (ACLMS) demonstrated restricted flexion
during the stance phase, ranging approximately 5 degrees. The limited knee flexion
demonstrated by Subject 5 can be explained by quadriceps avoidance gait. The subject
avoided firll use of the quadriceps as these muscles eccentrically contract to control the
lowering of the body during the initial flexion period. Quadriceps avoidance resulted in
limited knee flexion during this phase. A prolonged period of restricted flexion was
observed, as the action occurred during the initial 25% of the gait cycle. The longer
initial flexion period compensated for the limited flexion of the knee joint, extending the
time allowed for the deceleration of the limb. Differences between the two subjects were
also found during the extension period of the stance phase. Subject 4 demonstrated
limited extension at the knee joint of 5 and 10 degrees for trials one and two respectively,
while during the preceding period the knee had flexed 15 degrees. This limited extension
seen at the knee joint might be an adaptation to restrict any movement of the femur over
the tibia which is primarily controlled by the anterior cruciate ligament. Subject 5
performed “full extension” of the knee joint, since the knee joint returned to 10 degrees
of flexion. Maximum flexion reached during the swing phase was 70 and 60 degrees of
knee flexion for Subjects 4 and 5 respectively. At the completion of the gait cycle,

marked by second foot contact, the knee was flexed approximately the same amount as at

68
the initiation of the cycle analyzed. Subject 5 demonstrated a greater knee extension

range during the second foot contact of the cycle.

 

 

 

   
 

 

 

  

 

 

 

Knee FlexionIExtension Angular
80 “r Displacement
70 - ACLM4
.3. 50 ,L ................ACLM5 Toe or
.9. ____Control
a E 50 .
E s 40 ..
r s
g 30 ..
g 20 .
In
10 . c
0 IL l
0% 20% 40% 60% 80% 100%

 

 

 

Figure 24: Knee Flexion/Extension Angular Displacement under the Unfatigued
Condition. ACL-reconstructed Group.

Due to differences in the angular displacement between both subjects, the angular
velocity graphs will be analyzed separately (see Figure 25). Differences in the timing,
and in the velocity magnitudes were observed between the treatment and the control
groups data. Subject 4 presented the same timing and magnitude in the velocity of the
knee during the initial 20% of the gait cycle, as the control group. Subject 5 had a
smaller velocity magnitude over a larger period, which was due to the restricted knee
flexion presented during the initial 20% of the cycle. From 20% to 40% of the gait cycle,
Subject 4 demonstrated the same velocity pattern as the control group. However, the
velocity values remained close to the 0 range as compared to the control group. This
difference in magnitude was due to the restricted knee extension presented by the subject

from 20% to 40% of the gait cycle. Although a normal displacement pattern was

69
presented by Subject 5, differences in velocity with the control group were due to the

limited range and prolonged flexion/extension phase during midstance. Although this
subject presented restricted flexion, the extension range matched the flexion range during
the initial part of the stance phase. Both subjects presented lower velocity magnitudes
prior to toe-off, and during the swing phase than the control group. Subject 5 exhibited a

slower rate of deceleration of the knee joint prior to foot contact, when compared to the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

other subjects in the study.
.00 ,, Kn“ FWWM Anal"! Velocity 400 Knee FlexionIExtensicn Angular Velocity
Aer-M4 Suhiect 4 " Subject 5 fl
“4 ..... W
200 a. a ,
g 1m fl Midstance ’ ‘2
a“ ‘
0 Fc 1R3. 1 e 1 1
40 ‘. 60% (80% 100%
.100 .1 f FC
,Toedl'
-200 .. s ,0
rte-1t gel?”
300 -.
(a)

 

Figure 25: Knee Flexion/Extension Angular Velocity under the Unfatigued Condition.
(a) Subject 4 (b) Subject 5.

The angular acceleration graphs of Subjects 4 and 5, under the unfatigued
condition are presented in Figure 26. The same acceleration pattern as the one presented
by the control group was seen in Subject 4. The acceleration graph for Subject 4 when
compared to the control group exhibited smaller magnitudes during the gait cycle.
Subject 4 had smaller velocity magnitudes between 20% and 40% of the cycle. This
same relative difference in magnitude was observed between 25% and 60% of the cycle

in the acceleration graph.

 

70
Subject 5 presented differences in both timing and magnitudes when compared to

the control group. The magnitude of the first acceleration period was smaller than the one
presented by the control group. This lower magnitude of acceleration was seen during a
prolonged period of the stance phase. The deceleration period had smaller magnitudes
over the same period of time as the control group. Extension at the knee joint during the
stance phase was performed at a slower rate than the control group, due to a smaller
range of motion exhibited during the same time period. The acceleration values during

the swing phase were also lower in magnitudes than those seen by the control group.

 

 

Knee FlexionlExtension Anguls Knee FlexionlExtenaion Angular
' Accehraflon-Subjecu " Acceleration-Subjects

 

 

 

 

 

 

 

 

 

 

‘ 0
stool: OJcIe \r' SEGIItCIcle V

 

 

Degraeslsacondz
§§§§ .1838 S
.\
9
§
Degreeslsecondz
. in e
. 3:?“
§
11'
Z
§ fl...

.3000.
4000..

(a) (b)
Figure 26: Knee Flexion/Extension Angular Acceleration under the Unfatigued
Condition. (a) Subject 4 (b) Subject 5.

 

 

 

 

 

 

Abduction/adduction angular displacement graphs for the unfatigued condition
are presented in Figure 27. Both subjects in the ACL-reconstructed group presented a
similar pattern of the frontal motion of the knee, which closely resembled the normal
pattern. At foot contact both subjects exhibited a neutral position at the knee joint.
Throughout the stance phase, Subject 4 demonstrated a 5 degree adduction at the knee.

Subject 5, experienced fluctuations of +/- 2 degrees during the initial 50% of the gait

7]
cycle. Both subjects abducted at knee during the first half of the swing phase. Subject 4

reached maximum knee abduction of 15 degrees, while Subject 5 had a maximum value
of 10 degrees. Knee adduction was initiated past midswing to return the knee to the

neutral position at the completion of the gait cycle.

 

Knee Abduction/Adduction Angular
Displacement
| v z

 
 

.s
U!
I

.5
0

(hour
I"

'8
W
O \

  
 
 

Degrees
Add.(-)IAbd.(+)

Midstanee

llcalt Cycle

 

 

 

Figure 27: Knee Abduction/Adduction Angular Displacement under the Unfatigued
Condition. ACL-reconstructed Group.

Angular velocity and acceleration graphs for the unfatigued condition are
presented in Figures 28 and 29, respectively. The velocity pattern presented by Subject 4
during the stance phase, was smoother when compared to the pattern presented by
Subject 5. The angular velocity at the knee joint, for Subject 5, was determined by
changes in magnitude of displacement throughout the stance phase. Adduction at the
knee was illustrated by a smoother graph for Subject 4. When analyzing the acceleration
graphs presented by both subjects, some differences in patterns were identified. The
abduction/adduction angular acceleration of the knee presented rapid changes in
magnitude, for Subject 4. When the velocity graph, for the same subject, was carefully

analyzed, small and abrupt changes were observed during the initial 70% of the cycle.

72
These changes lead to the high number of magnitude changes presented on the

acceleration graph. However, the acceleration magnitudes were tight around zero. The
pattern presented by Subject 5, showed lower variability in the magnitudes, when
compared to Subject 4. During midswing, Subject 4 exhibited the highest acceleration
magnitude of the knee. This acceleration peak was not demonstrated by Subject 5. The
difference in the patterns was due to the difference in displacement magnitudes presented

during the swing phase, by each subject.

 

 

Knee AbductionIAdductlon Angular Knee AbductionlAdduetion Angulu
150 T Velocity - Subject 4 15° ~~ Velocity - Sula-ct 5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(a)
Figure 28: Knee Abduction/Adduction Angular Velocity under the Unfatigued
Condition. (a) Subject 4 (b) Subject 5.

 

73

 

Knee AbductionlAddueflon Angular Knee Abduction/Adduction Angular
Acceleration-Subject4 Manon-SubjectS
2500 ..
2000 ..

 

Degreeslsecondz

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 29: Knee Abduction/Adduction Angular Acceleration under the Unfatigued
Condition. (a) Subject 4 (b) Subject 5.

Under the fatigued condition, both subjects forming part of the treatment group
demonstrated adaptations to the flexion/extension pattern experienced during the
unfatigued state. At foot contact the knee was flexed approximately 10 degrees, showing
a consistent pattern with the amount of flexion demonstrated during the unfatigued state.
During initial flexion both subjects increased the range of movement. However, Subject
5 demonstrated limited ranges in flexion when compared with the normal angular
displacement, see Figure 30. The timing of peak initial flexion during the fatigued state
was consistent with that of the unfatigued state for Subject 4. Subject 5 showed a 5% of
gait cycle delay in peak flexion during the fatigued state. The flexion/extension range for
Subject 4 was close to normal values. During the swing phase Subject 5 demonstrated a
decrease in the flexion magnitude during the fatigued state, when compared to the

unfatigued state.

74

 

 

 

  
   

 

   

 

 

 

Knee FlexionlExtension Angular
3° " Displacement
A 7° . ACLM4
a so .............. ACLMS
: -1
.2 . . . . .ACLM4-UF
e 3 5° . ......... ACLMS-UF
is 40 -.
° E’
8 2 30 -.
0
S
3 2° ‘ch .
10 m- " ”an. .“\ ’y \‘
a..." “m?” %Gait Cycle 1.0
0 1 1 1 + 1
0% 20% 40% 60% 80% 1min,

 

 

 

Figure 30: Knee F lexion/Extension Angular Displacement under the Fatigued Condition.
ACL-reconstructed Group.

The angular velocity graphs of the knee joint under the fatigued condition are
presented in Figure 31. Subject 4 had a velocity pattern in the fatigued condition very
similar to that shown by the control group under the unfatigued condition. During the
fatigued state Subject 4 demonstrated normal flexion/extension of the knee joint during
the stance phase. The increase in the flexion/extension range during the fatigued state led
to a normal velocity graph. The lower velocity values seen in the graph of the unfatigued
state during the extension period, were not present during the fatigued state. Greater
velocity magnitudes were seen prior to toe off, since the knee had to flex over a greater
range to prepare the limb for the swing phase under the fatigued state when compared to
the unfatigued condition. Subject 5 had similar angular velocity patterns between the
unfatigued and fatigued states. Some timing differences were observed due to the
changes presented on the angular displacement of the knee joint during midstance, under

the fatigued state.

75

 

 

 

400 Knee FlexionlExtension Angular Velocity 400 Knee FlexionIExtenslon Angular Velocity
" Subject 4 " Subject 5
" '~ 300 .. W“
..... matted

 

 

 

 

 

 

 

 

 

   

cool

 

 

 

 

Figure 31: Knee FlexiSBExtension Angular Velocity under the Fatitried Condition. (a)
Subject 4 (b) Subject 5.

The angular acceleration graphs for the fatigued condition of Subjects 4 and 5 are
presented in Figure 32. As expected, the acceleration graph for Subject 4 under the
fatigued condition displayed the same pattern as the graph of the unfatigued condition for
the control group. The pattern presented by Subject 5 resembled the pattern presented by
the same subject under the unfatigued condition. Similar acceleration magnitude was
exhibited during midstance, however, under the unfatigued condition a steeper slope was
observed on the acceleration curve. This change in the slope was due to a shorter period
of knee flexion. The knee flexed a greater range during the fatigued condition for Subject
5, leading to a higher acceleration magnitude during the stance phase. In addition, a
greater range of knee flexion during the swing phase, for the fatigued state, was shown

by a higher acceleration magnitude for this condition when compared to the unfatigued

condition.

 

76

 

 

 

 

 

 

 

 

 

 

 

   

 

 

 

 

 

 

 

 

Knee Flexion/Extension Angular Knee FlexionIExtenslon Angular
“3°01" Acceleration-Squ mv MIMI-Slims
3000 .. 3000 « Tailored
2000 .. 2000 """ mm
Mldstarlce
1000 .. E 1000 ..
3 FC
0 '- 0 .
0 20%
-1000 .. E4000 x"
-2000 . 40001.
rte-notch . resultant.
.4000 .L 4000 .1
(a) (b)

Figure 32: Knee Flexion/Extension Angular Acceleration under the Fatigued Condition.
(a) Subject 4 (b) Subject 5.

Several differences were seen in the abduction/adduction angular displacement
pattern in the subjects of the ACL-reconstructed group when both tested conditions were
compared. The abduction/adduction angular displacement graphs for the fatigued
condition for both Subjects 4 and 5 are illustrated in Figure 33. Subject 4 maintained the
same displacement pattern under both the unfatigued and fatigued conditions, showing
differences in magnitude and timing during the swing phase. During the swing phase of
the fatigued state, the maximum knee abduction magnitude for Subject 4 was reduced.
Magnitude of maximum knee abduction was 10 degrees, and this knee position was
maintained until the completion of the gait cycle. At foot contact, Subject 5, exhibited 5
degrees of adduction at the knee joint. During the stance phase, Subject 5 abducted the
knee joint and reached the neutral knee position at 40% of the gait cycle. The knee
maintained a relatively constant adduction displacement throughout the stance phase.
Subject 5 demonstrated the same angular displacement pattern, during the swing phase,

under both tested conditions.

77

 

Knee Abduction/Adduction Angular

 

 

 

 

 

 

25 - Displacement
............... ACLM5
+ 15 ..... ACLM4-UF
. E ......... ACLMS-UF
g; 10 . Toe off , “1.“:
g ‘L 5 d. I‘ 1' "2.5.
E ",z’j.’ ,0 \t‘
< 0 ”E % "N I , t’ ‘
_5 ,, '=-" 'W a" fit 30% 100%
-10 PC PC
9663i! Cycle

 

 

 

Figure 33: Knee Abduction/Adduction Angular Displacement under the F atigued
Condition. ACL-reconstructed Group.

Abduction/adduction angular velocity and acceleration graphs for the fatigued
condition for Subjects 4 and 5 are presented in Figures 34 and 35. Magnitude changes
were observed for Subject 4 when the velocity and acceleration patterns under the
fatigued state were compared to those presented under the unfatigued state. Lower
velocity magnitudes were observed during the fatigued state. The acceleration pattern
presented by Subject 4 under the fatigued state, compared to that presented by Subject 5
under the unfatigued condition. The peak acceleration value was smaller in magnitude
during the fatigued condition than the unfatigued condition, due to a smaller abduction
displacement which occurred during the swing phase for Subject 4. Under the fatigued
condition, Subject 5 displayed a constant velocity value throughout the stance phase.
Knee acceleration was 0 degrees/second2 for the initial 60% of the gait cycle. This
acceleration was due to the uniform abduction displacement presented by the subject

during the initial portion of the gait cycle.

78

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Knee AbductionlAdductlon Angular Knee Abduction/Adduction Angular
15° 1. Velocity - Subject 4 15° 1- Velocity - Subject 5
100 ..
50 <- Midstalce FC
g FC ’
2 °- "
0
3 20% 100%
El .50 J' Toe-cl)!"
8
.100 .1
stout 011*
.150 .t -150 ..
%Galt Cycle _l'fattguorl
.200 .l .2001 ..... Ullalaued
(a) (b)

Figure 34: Knee Abduction/Adduction Angular Velocity under the Fatigued Condition.
(a) Subject 4 (b) Subject 5.

 

 

Knee AbductiontAdduction Angular Knee AbductionlAdductlon Angular

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 35: Knee Abduction/Adduction Angular Acceleration under the Fatigued
Condition. (a) Subject 4 (b) Subject 5.

Muscular activity characteristics under the unfatigued condition for Subject 4 are
presented in Figure 36. The subject demonstrated greater intensity of muscular activity
for the hamstrings group when compared to the intensity level of the quadriceps group.
The quadriceps were active from 10% to 50% of the gait cycle. This portion of the gait

cycle corresponds with knee extension during midstance and the passive lift off phase.

 

79
Even though the quadriceps were not contracting during the initial 20% of the gait cycle,

indicating quadriceps avoidance, the gait characteristics were not representative of
quadriceps avoidance gait. In quadriceps avoidance gait, limited flexion occurs over the
initial 20% of the gait cycle. However, for Subject 4 a full flexion range was seen during
the stance phase. The quadriceps were active during the initial 30% of the cycle for the
second trial tested. The activity pattern observed for the hamstrings group was also
different for the two trials analyzed. During the first trial, the subject presented an active
hamstrings group during the initial 55% of the gait cycle, and a second activity phase for
the last 10% of the gait cycle. In the case of the second trial, the same subject exhibited

activity on the hamstrings between 10% and 90% of the gait cycle.

 

 

Emmcordhgs-Subjact4-Trld1 ELBRecordhgs-Subject4-Trid2

 

 

 

 

 

 

 

Figure 36: Muscular Activity Patterns for the Quadriceps and Hamstrings Muscle Groups
under the Unfatigued Condition. Subject 4. (a) Trial 1 (b) Trial 2.

The muscular activity pattern presented during the fatigued state for Subject 4 is
illustrated in Figure 37 . Under the fatigued condition, Subject 4 demonstrated greater

intensity of contraction for the quadriceps group when compared to the intensity of

80

contraction demonstrated by the hamstrings group. Quadriceps activity was present
during the initial 20% of the cycle, and from 50% to 90% of the gait cycle. The
quadriceps acted to restrict knee flexion during the initial 20% of the gait cycle. The
activity of the quadriceps muscles recorded during the latter part of the cycle was due to
flexion at the hip joint and extension of the knee joint prior to second foot contact.
Hamstrings activity was exhibited for the initial 30% of the cycle and 40% of the gait

cycle prior to second foot contact.

 

EMG Recordings - Subject 4

  

IHa'“s o .e i

£199?“5 8 E: .e at
N

IHamS'NW" %GaitCycle 8 3

 

 

100%

a Grads-Norm

Figure 37: Muscular Activity Patterns for the Quadriceps and Hamstrings Muscle Groups
under the Fatigued Condition. Subject 4.

 

II. LINEAR MOTION
A. Normal Data

Linear parameters of gait were analyzed with the purpose to obtain information
about the relative movement of the knee joint with respect to the ankle and hip joints.
Hip, knee and ankle joint markers defined the two segments of the lower extremity. The

relative movements of these segments were used to define the knee angle for angular data

81
analysis. All subjects walked in the positive X direction, according to the coordinate

system used in the study. An increase in joint displacement along the X-axis would
indicate the advancement of the joint along the walkway. Linear displacement data for
the hip, knee and ankle joints were analyzed in relation to the alignment of the joints at
specific periods in the gait cycle. Joint alignment was exhibited when the position of two
or all three joints was the same along the X-axis, see Figure 38. The same relative
alignment of two adjacent joints along the X-axis, positioned the defined body segment
perpendicular to the ground.

Six aligned positions of the three joints occurred during the gait cycle. At foot
contact, the ankle joint is the joint furthest from the origin, therefore demonstrating the
greatest value along the X-axis. Once the flat foot position is obtained, movement at the
ankle joint is limited throughout the stance phase. Following foot contact, knee flexion is
performed. Flexion at the knee resulted from the shank segment moving faster than the
thigh. This forward movement of the shank caused the first ankle-knee alignment early in
the stance phase. At approximately 20% of the gait cycle, as the knee reached maximum
flexion, the position of the knee joint along the X—axis was furthest away from the origin.
At this point an ankle-hip alignment is observed. Following maximum flexion of the
knee, the forward displacement of the knee joint decreased. While the hip joint
maintained the same rate of displacement, the faster moving hip joint caught up with the
knee allowing for the first hip-knee alignment during midstance. The hip joint continued

to move at a faster rate than the knee joint until the initiation of the second knee flexion

82

 

Knee Flexion/Extension angular

displacement
60 ,_

50 .._

  
    
    

“0 *’ Toe off
30 11-

Degrees

Extension(-)IFlexlon(+)

20 4» Midstance

10 ,rc FC

96 GaitCycle

 

 

1
fl T

0% 20% 40% 60% 80% 100%

 

 

 

Stance Phase Swing Phase

11.

Linear Displacement about the X-axis

  

 

 

250 _-
200 ..1_

100

M idstance

 

cm
“
O

 

 

 

 

 

 

 

 

50 __ . _AIII(IG
Knee
Hip
0 1 e 1 1 i
0% 20% 40% 60% 80% 100%

$6 Gait Cycle

 

 

 

Figure 38: Joint Alignment

period. Flexion of the knee joint increased the rate of displacement of the knee joint,
allowing for the second alignment of the hip and knee joints prior to toe off. As the limb

prepared to enter into the swing phase, the ankle joint initiated its forward movement.

83
During the swing phase the ankle joint demonstrated the highest velocity of all three

joints. Flexion at the knee joint caused the knee to be the furthest point from the origin,
and as it occurs during the stance phase, an alignment of the hip and ankle joints is
observed at the point of maximum knee flexion. Following midswing, the highest
velocity is seen in the shank segment, allowing the ankle joint to catch up with the knee
joint. The ankle-knee alignment occurs late in the swing phase and is the last alignment

seen during the cycle.

B. Control Group

As illustrated in Figure 39, all the subjects in the control group demonstrated
similar linear displacement patterns of the lower extremity joints during the unfatigued
state. In addition, all the subjects demonstrated the six normal alignments of the joints
throughout the gait cycle. The analysis of the linear displacement of the joints was
focused primarily on the stance phase, since most of the adaptations in gait characteristics
occur during this period. The first alignment of the ankle and knee joints was found at
approximately 10% of the gait cycle. As flexion at the knee joint continued, the hip and
ankle joints aligned at approximately 25% of the cycle. This second alignment was
observed past the maximum flexion point which occurred at 20% of the cycle. Prior to
the point of “full extension” of the knee during midstance, the first alignment of the hip
and knee joints was observed, occurring at 37% of the gait cycle. The second alignment
between the hip and knee joints was observed prior to toe off at approximately 62% of

the gait cycle. The differences shown by Subject 2 during the angular displacement of the

34

knee joint, were also observed when analyzing the linear displacement pattern of the
knee joint for this subject. The linear displacement graph for the unfatigued condition for
Subject 2 (Figure 39b) illustrated differences in the slope of the knee’s linear
displacement graph during the stance phase when compared to the other subjects in the
control group. Specifically, Subject 2 had limited extension of the knee joint during the
stance phase and following maximum flexion, the knee’s linear displacement plateaued.
This plateau was longer for Subject 2 with respect to the other subjects, indicating a

prolonged flexion period as there was limited extension at the knee joint.

 

Linear Displacement Linear Displacement
Control Group Subject 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(a) (b)
Figure 39: Linear Displacement under the Unfatigued Condition. (a) Control group (b)
Subject 2.

When the linear velocities of the three joints under the unfatigued condition were
examined several characteristics were found and are illustrated in Figure 40. First,
velocity at the ankle joint for the initial 10% of the gait cycle had a negative slope. The
ankle joint was decelerated to O cm/sec, and maintained this magnitude until 40% of the
cycle. This velocity magnitude was due to the limited displacement presented at the ankle

joint during the first portion of the stance phase. Following this initial period of the

85

stance phase, the velocity of the ankle joint increased until midswing, and then decreased
as the joint slowed down prior to second foot contact.

At the knee joint, the velocity decreased during the initial flexion period and
increased from the maximum flexion point until toe off. This velocity pattern
corresponds to the advancement of the body over the supporting leg. During the second
flexion period, the slope of the velocity curve was reduced past midswing as the velocity
at the knee joint decreased.

The linear velocity of the hip joint was of a smaller magnitude than the other two
joints which indicated that the rate of the hip’s linear displacement was relatively
constant throughout the gait cycle. A slight negative slope was observed for the initial
40% of the cycle. However, the hip’s linear velocity pattern did not present any specific

characteristics that could be identified during the gait cycle.

 

 

Linear Velocity
Control Group
400
3w “ — e
Knee
250 WHP

 

 

 

cmleec

§ §
.3
g

 

 

 

 

v. Gait Cycle

 

 

 

Figure 40: Linear Velocity under the Unfatigued Condition. Control Group.

Linear accelerations of the ankle, knee and hip joints under the unfatigued state,

are presented in Figure 41. For the initial 15% of the gait cycle, the slope of the

86

acceleration graph was positive. From 15% to 40% of the gait the acceleration values
approximated 0 cm/sec2 due to the constant velocity presented at the ankle joint. An
acceleration period of the ankle was observed from 40% to 65% of the cycle due to
preparation for toe off, and decelerated following toe off until midswing. The ankle joint
accelerated following midswing, to move the foot in front of the knee joint as the limb
prepared for foot contact.

At the knee joint, a deceleration period was observed for the initial 15% of the
gait cycle. The joint decelerated as the foot struck the ground and flexion at the knee
joint controlled the forward motion of the body. The knee accelerated from 15% to
approximately 55% of the gait cycle, decelerated during the initial portion of the swing
phase, and then accelerated from midswing to foot contact. Due to the relatively constant
velocity observed at the hip joint throughout the gait cycle, the acceleration magnitudes

2
were close to O cm/sec .

 

 

cmlsecz

 

 

 

 

 

% Gait Cycle

 

 

 

Figure 41: Linear Acceleration under the Unfatigued Condition. Control Group.

87
Under the fatigued condition, the linear displacements of the hip, knee and ankle

joints followed their respective similar pattern as that pattern presented under the
unfatigued condition. However, timing differences were found throughout the gait cycle
under the fatigued condition. The linear displacements of the hip, knee and ankle joints

are shown for the control group under both conditions in Figure 42. A greater range of

 

 

Lilear Dieplaeermnt
Control Group
350
300 ..
250 ..

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(a)
Lhear Displacement Linear Displaeermnt
Control Group - F Control Group - UP
350 350
300 .. $0
m uh- 250 db-
ZCXJ 4» ..-°- 200 ._ ________
5 T“ 0” /"';::.v «I .4 8 Tu w ll” ”#1.”!-
150 -» can-v" “ 150 :3”
Mfi‘wd.‘ ‘u-va-fw‘
100 .t ,,,,...-—-;;-,::m"'”" 100 4._,..-"",;":»~"m'
31.,va ......... Knee QM“ .......... Knee
50 .. Midstance , 50 .. Midstance .
WHlp .........Hip
0 . : : r 0 : : : .
0% 20% 40% 60% 80% 100% 0% 20% 40% 60% 80% 100%
% Gait Cycle % Gelt Cycle
0)) (C)

Figure 42: Linear Displacement under the Fatigued Condition. (a) Control group (b)

Knee-hip Comparison under the Fatigued Condition (c) Knee-hip Comparison under the
Unfatigued Condition.

88
knee flexion/extension was demonstrated during the fatigued state when compared to the

unfatigued condition. Under the fatigued condition, the first hip-knee alignment occurred
at 42% of the gait cycle instead of 37% 0f the cycle. This delay was due to the longer
period taken to flex and extend the knee joint. The second hip-knee alignment was
observed at approximately the same time during the stance phase for both conditions,
suggesting greater extension of the knee joint at toe off when comparing the fatigued to
the unfatigued conditions.

The velocity and acceleration graphs for the fatigued condition are presented in
Figures 43 and 44. Both the velocity and acceleration patterns showed similar
characteristics at the knee and hip joints as those observed under the unfatigued state.
During the fatigued condition the first hip-knee alignment occurred later during the
stance phase when compared to the unfatigued state. This difference in timing was shown
as a longer negative slope on the velocity graph under the fatigued condition. The knee
was decelerated over a longer period of time due to the longer flexion/extension phase
presented at the knee joint, from foot contact to 35% of the cycle. Since the second
alignment observed for the hip and knee joints occurred at the same percent of the gait
cycle under both conditions, the magnitude of the velocity graph increased. Under the
fatigued condition, the knee joint had a shorter period in which to recover and align with
the hip joint. Therefore, the velocity graph presented a positive slope reaching a greater
magnitude. This faster rate of change of the displacement of the knee joint can also be

observed on the acceleration graph. The knee was accelerated to a greater magnitude

89
over a longer period of time during the fatigued condition, when compared to the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

unfatigued state.
Linear Velocly Linear Velocity
Control Group - F Control Group - UP
400
a v _Arkle
._.._ Knee
30° 4* “WI-up
250 . Toe off
200 .. IN
8 Midstance ' \ E
so .
E 100 ...... L \ s
1pc-.\::wu. Man \4
so .. \\ / PC
0 -=___ . "—9; ,_ .L
.50 20% 40% 60%
-100
% Gait Cycle
(20 (b)

Figure 43: Linear Velocity under the Fatigued and Unfatigued Conditions. Control
Group. (a) F atigued (b) Unfatigued.

 

 

Linear Acceleration
Control Group - F

 

 

 

cmlsecz
emlsecz

 

 

 

 

 

 

 

 

 

%Galt Cycle

 

 

 

 

 

 

 

(b)
Figure 44: Linear Acceleration under the Fatigued and Unfatigued Conditions. Control

Group. (a) F atigued (b) Unfatigued.
As illustrated in Figures 43 and 44, the ankle joint showed differences in both the
velocity and acceleration patterns under the fatigued condition, when compared to the

unfatigued condition. A relatively constant velocity of 0 cm/sec was presented for the

 

90
initial 40% of the gait cycle. As the ankle joint prepared for toe off the velocity of the

joint was increased. However, the magnitude of the increase was restricted during the
fatigued condition when compared to the unfatigued state. During the fatigued condition
the ankle joint demonstrated a negative slope in the velocity graph past the point of toe
off. Under the unfatigued condition the changes in the direction of the slope did not
occur until midswing. The acceleration graph for the control group under the fatigued
condition, illustrates the reduced magnitude of the acceleration of the joint form 40% to
60% of the gait cycle. A deceleration period is presented through toe off, and at 75% of

the gait cycle the joint accelerates to prepare the joint for foot contact.

C. ACL - Reconstructed Group

Linear displacement graphs for Subjects 4 and 5 under the unfatigued condition
are presented in Figure 45. Due to the differences observed in the linear displacement
graphs, data for both subjects will be presented and discussed. The knee angular
characteristics presented by Subject 4 under the unfatigued condition were similar to
those presented by Subject 2 under the same condition. (See Figures 45 a and b). As
expected, the linear displacement graph for the hip, knee and ankle joints were similar
for both subjects. During midstance the forward displacement of the knee joint was
limited, while Subject 2 demonstrated normal initial flexion of the knee joint, extension
of the joint during midstance was limited. At the point of maximum knee flexion (20%

of the gait cycle) in the stance phase, the rate of change of the knee’s displacement

91
decreased with respect to the hip joint. Due to the limited extension of the knee joint

during the stance phase, the joint maintained a slower rate of displacement to allow for
the second hip-knee alignment. Timing of the rest of the alignments that occurred

throughout the gait cycle were within the normal ranges of percent of gait cycle.

 

 

Linear Displacement
Subject 2

 

 

cm
oggsgsgs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(a) (b)
Linear Displacement Linear Dieplaeermnt
Subject 5 Control Group
350
300 ..
250 ..
200 r.
E
0 150 .
100 .
so .L
o
SSGalt Cycle soc-It were
(6) (d)

Figure 45: Linear Displacement under the Unfatigued Condition (a) Subject 4 (b) Subject
2 - Control Group (c) Subject 5 ((1) Control Group.

Linear displacement patterns presented by Subject 5 under the unfatigued
condition presented differences when compared to the control group patterns of the same

condition (see Figures 45 c and (1). Subject 5 showed limited flexion of the knee joint

 

 

92
during the stance phase. In addition, the linear displacement characteristics had later

alignments of the ankle-knee joints during the stance phase than the control group. The
first ankle-knee alignment occurred at 21% of the gait cycle. This delay in the first
alignment did not cause a delay for the rest of the alignments. The second ankle-hip
alignment was observed at about the same period on the stance phase as the control
group. A steeper slope was observed in displacement for the knee joint of Subject 5,
when compared to the control group. Flexion of the knee joint aids in the forward
advancement of the knee joint. The limited flexion experienced at the knee joint caused
the displacement of the hip and the knee to be parallel for the initial portion of the stance
phase. Flexion at the knee advanced the knee joint further in front of the hip and ankle.
However, the time period during the stance phase between the ankle-hip alignment and
the first hip-knee alignment was reduced as a result of the limited flexion. A longer
percent of the cycle elapsed between the first and second hip-knee alignment. This time
difference was due to the longer extension period demonstrated by the knee joint during
the stance phase. The prolonged knee extension caused a delay in the initiation of the
second knee flexion period, therefore, requiring more time for the knee joint to catch up
with the hip. The pattern of the ankle joint displacement for Subject 5 was different to
the pattern presented by the other subjects in the study. During the last 10% of the gait
cycle the slope of the displacement graph was reduced for the subject in the control
group and Subject 4 of the treatment group. In the case of Subject 5, the slope of the
ankle joint displacement was maintained from the point of toe off to the completion of

the cycle.

93
The linear velocity for the three joints under the unfatigued condition are

presented in Figures 46. The linear velocity of the knee joint presented a negative slope
following foot contact, for both subjects in the treatment group. Due to the restricted
knee flexion experienced by Subject 5 the slope of the velocity graph for the knee was
not as steep as the one presented by Subject 4. Subject 5 had a longer period of
deceleration of the knee joint to 40% of the cycle, due to the reduced ability of the joint
to decelerate the limb after foot contact. At 40% of the gait cycle the slope of the knee
velocity became positive. The velocity of the knee joint increased until the point of the
second hip-knee alignment. The velocity graphs of the hip and ankle joints were found to
be similar for both subjects of the treatment group. The velocity of the ankle joint for
Subject 5 showed a different pattern after midswing, than that presented by the other
subjects. From midswing to the completion of the cycle, the velocity of the joint
decreased to the same magnitude presented at foot contact, as presented by the control
group and Subject 4. Subject 5 demonstrated a decrease in the velocity after midswing,
however, the magnitude from toe off to second foot contact was only reduced by half the
expected value. This difference in the velocity pattern was due to the observed rate of

change of the displacement graph during the last 10% of the cycle.

94

 

 

Linear Velocity Lined Velocty
400 Subject 4 Subject 5
—Ankle
‘ __Knee
. Wl-lip

 

 

 

    

 

 

 

 

 

 

cmlsec

cmlaec

g .:"':“""""Meeeeeeeem'

    

 

 

__

 

 

l
f

.50 20% 40% 60% 80% 100%

 

 

 

 

 

 

 

 

 

 

 

-100 % Gait Cycle
(3) (b)

 

 

 

 

 

 

cmlsec

 

 

 

 

 

 

 

 

Figure 46: Linear Velocity under the Unfatigued Condition. (a) Subject 4 (b) Subject 5
(c) Control Group.

The acceleration graphs, illustrated in Figures 47 a and b, showed differences in
magnitudes at the knee joint between Subjects 4 and 5. The acceleration and deceleration
magnitudes were smaller for Subject 5. However, the acceleration magnitudes for
Subject 4 were smaller than those presented by the control group. At the ankle joint,
Subject 4 had a similar acceleration pattern as that demonstrated by the control group.
After the point of toe off the slope of the acceleration graph for Subject 4 showed some

differences when compared to the control group. From toe off to midswing, the 310pe

95
the acceleration graph was 0 for Subject 4, indicating a constant rate of change in the

velocity of the joint. Subject 4 also presented a smaller deceleration magnitude prior to
the completion of the cycle. The acceleration magnitudes for the ankle joint for Subject 5
were smaller when compared to those presented by the rest of the subjects in the study.
The acceleration/deceleration period was shorter for Subject 5, due to a later initiation of

the forward displacement at the ankle joint.

 

 

 

 

cmlsecz
cmlsecz

 

 

 

 

 

 

 

 

 

 

 

%GaltCycle

 

 

 

 

 

 

 

 

 

 

cmlaec2

 

 

 

 

 

SSGaIt cycle

 

 

 

(C)
Figure 47: Linear Acceleration under the Unfatigued Condition. (a) Subject 4 (b) Subject
5 (c) Control Group.

96
Under the fatigued condition, shown in Figure 48, the linear displacements of the

hip, knee, and ankle joints showed some temporal differences when compared to the
unfatigued condition. Subject 4 had a later alignment than under the unfatigued condition
between the ankle and knee joints occurring at approximately 20% of the gait cycle. In
addition, a shorter period was observed between the first and second hip-knee alignment,
when compared with the unfatigued condition. Subject 5 demonstrated an earlier ankle-
knee alignment during the stance phase under the fatigued condition than the unfatigued
condition, which led to a longer percent of cycle between the ankle-hip and the first hip-
knee alignments. The slope of the knee’s displacement graph was steeper for the fatigued
condition when compared to the displacement under the unfatigued condition for Subject
5. This change in the slope characteristics was due to greater knee flexion experienced
under the fatigued condition, allowing the knee joint to displace faster than the hip joint
during the initial portion of the stance phase.

Linear velocity and acceleration graphs for the fatigued condition are presented
for both subjects in the ACL reconstructed group. The velocity and acceleration graphs
obtained under the fatigued condition were compared to the graphs for the unfatigued
condition for the same subject. These patterns are illustrated in Figures 49 and 50,
respectively. Subject 4 demonstrated a steeper negative velocity slope occurring from
foot contact to approximately 30% of the gait cycle. This change in the slope of the
velocity graph was due to a greater flexion range presented by the subject during the

stance phase. The larger flexion at the knee joint led to a higher rate of change on the

97

 

 

 

cm
osseasw

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

cm
orgasm.“

 

 

 

 

 

 

 

 

 

 

 

 

 

(C) (6)
Figure 48: Linear Displacement under the F atigued and Unfatigued Conditions. (a)
Subject 4 - Fatigued (b) Subject 4 - Unfatigued (0) Subject 5 - Fatigued ((1) Subject 5 -
Unfatigued.
displacement of the joint. The magnitude of the knee’s velocity displayed at toe off was
greater under the fatigued condition than under the unfatigued condition. The ankle joint
also displayed a steeper slope on the velocity graph during the swing phase for the
fatigued condition when compared to the unfatigued state. This subject’s acceleration

graph illustrated the difference found in the slope of the velocity of the knee joint by a

decrease in acceleration magnitudes presented at the knee joint. The ankle joint presented

 

98
higher acceleration values under the fatigued condition than under the unfatigued

condition. Additionally, the ankle joint had a more pronounced acceleration change from

toe off to midswing of the fatigued condition, when compared to the unfatigued

 

 

 

 

  
     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

condition.
Linear Velocity
Subject 4 - F
400
35° .. —Ankle
300 i __Knee Toe off
250 -,. WH‘P
/
g 20° " Midstance §
E 150 .. . E
o 100 4 L °
50 i '
0 -
500% 20% 40% 60% 80% 100%
-100 -100
%Gait Cycle 56 Gait Cycle
(a) (‘0)
Linear Velocity
Su 5-F
400 W
—Ankle
350 it __Knee
300 4. mm Hip
250 ..
200 ..
g 150 ”F0 Midstance g
0 100 ..M::L:...m.mw-m’”” ‘ E
5° “ /
0 , 1* i
.5005. 20% 40%
400 -100
%GaltCycle StGalt Cycle
(0) ((0

Figure 49: Linear Velocity under the Fatigued and Unfatigued Conditions. (a) Subject 4
- Fatigued (b) Subject 4 - Unfatigued (c) Subject 5 - F atigued (d) Subject 5 -
Unfatigued.

99

The differences in the linear velocity between the two tested conditions were less
pronounced for Subject 5. The only apparent difference presented in the knee velocity
pattern was a greater velocity magnitude found at toe off during the fatigued state. The
velocity pattern exhibited at the ankle joint was comparable to normal values, as opposed
to the difference in magnitude presented under the unfatigued condition. The acceleration
graph for the knee joint under both conditions presented similar patterns, for Subject 5.
Under the fatigued condition, the slope of the acceleration of the knee joint from 30% to
60% of the cycle was steeper than under the unfatigued condition. This was due to the
difference found on the magnitude of the velocity of the knee prior to the swing phase

between the two conditions.

HI. SUMMARY

Angular displacement data were presented only for the knee joint. The most
relevant differences in this study were those experienced during the stance phase of the
gait cycle. The control group demonstrated normal flexion/extension characteristics
under the unfatigued condition. An exception to this finding was Subject 2 of this group,
who showed limited extension during midstance. Under the fatigued condition, all
subjects in the control group had a greater flexion/extension range during the stance
phase, than under the unfatigued condition. The flexion/extension period lasted an
additional 5% of the gait cycle longer when compared to the unfatigued condition.
Increases in velocity and acceleration magnitudes over those in the unfatigued condition

were present during the fatigued condition.

100

 

 

 

 

    

Linear Acceleration
3 -
1500 ubject 4‘ F
1000 ..
500 .

Midstence

 

crnlsecz
cmlsecz

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

crnlsecz
cmisecz

 

 

 

 

 

 

 

 

 

 

%Galt Cycle swan Cycle

(0) ((1)
Figure 50: Linear Acceleration under the Fatigued and Unfatigued Conditions. (a)
Subject 4 - Fatigued (b) Subject 4 - Unfatigued (c) Subject 5 - Fatigued (d) Subject 5 -
Unfatigued.

 

 

 

 

 

The subjects forming the ACL-reconstruction group demonstrated adaptations in
the flexion/extension angular displacements of the knee joint. Under the unfatigued
condition, Subject 4 showed limited extension during midstance, while Subject 5
experienced limited flexion/extension during the entire stance phase. These gait

adaptations indicated similar characteristics as those presented during quadriceps

 

 

101

avoidance gait. With quadriceps avoidance gait, the subject limits the motion at the knee,
as a protective mechanism for the injured joint. Due to the differences experienced in the
angular displacement of the knee joint, the angular velocities and accelerations were of
lower magnitudes than those magnitudes found for the control group. A delay in the
flexion/extension pattern during the stance phase was also experienced by the treatment
group when compared to the control group.

During the fatigued state, Subject 4 demonstrated a normal flexion/extension
pattern during the stance phase. Subject 5 had a 5 degree increase in the flexion/extension
range when compared to the unfatigued condition. However, the range of motion was
lower than normal expected values. Under the fatigued condition, all subjects, except
Subject 1, experienced an increase in flexion/extension magnitudes during the stance
phase. The velocity and acceleration patterns, under the fatigued condition for Subject 4,
were similar in magnitude and timing to the patterns found for the unfatigued condition
for the control group. The flexion/extension pattern for Subject 5 was similar during both
tested conditions, leading to similar magnitudes in the velocity and acceleration patterns
under both conditions.

The results of the abduction/adduction angular displacements, velocities and
accelerations indicated less consistency among the groups and conditions tested, than for
flexion/extension. It is believed that this increase in variation was due to the small range
of motion experienced by the knee joint movement in the frontal plane, in combination
with the sagittal targeting. A wide range of abduction/adduction angular displacement

was experienced by the subjects in the control group. However, the greatest differences

102

between subjects were experienced during the swing phase. The velocity and acceleration
patterns showed numerous magnitude changes throughout the stance phase. When
comparing the unfatigued and fatigued conditions for the control group, the general
patterns were found to be the same under both conditions. Adaptations experienced by
the control group during the swing phase of the fatigued condition were shown by an
increase in magnitude of maximum abduction. Differences in velocity and acceleration
magnitudes were apparent when comparing both tested conditions. Although a similar
discrepancy in patterns was presented by the two subjects forming the treatment group,
the displacement patterns were more characteristic of displacements traditionally
presented as normal. The ACL reconstructed group’s changes in displacement for
abduction/adduction were less in number and magnitude when compared to the
unfatigued condition of the control group. As a result, both subjects experienced
velocities and accelerations of lesser magnitude than the control group.

Under the fatigued condition, Subject 4 demonstrated the greatest change in
pattern when compared to the unfatigued condition. Subject 4 had an increase in the
maximum abduction value during the swing phase, demonstrating a similar range of
motion as that presented by the control group under both conditions. Subject 5
maintained the same general pattern under both unfatigued and fatigued conditions. The
velocity and acceleration patterns of Subject 5 indicated a more controlled movement
during the fatigued state, due to the uniform motion characteristics presented under the

fatigued condition.

103
The muscular activity characteristics found for both conditions differed for all the

subjects tested. Under the unfatigued state, subjects in the control group showed a higher
intensity of contraction for the quadriceps group than the treatment group. However,
quadriceps firing patterns were different in timing for both tested subjects in this group.
In addition, hamstrings activity was observed during the later portion of the stance phase,
and the initial part of the swing phase for both subjects, instead of the expected
hamstrings activity for the initial 15% of the cycle, and from 75% to completion of the
cycle. Under the fatigued condition, the hamstrings demonstrated a higher intensity of
contraction when compared to the contraction of the quadriceps, under the same
condition. The pattern of activity again was different for both subjects. Under the
fatigued condition, Subject 2 demonstrated hamstrings activity during the full gait cycle.
This increase in muscle activity might be interpreted as a secondary mechanism for knee
stabilization. Subject 4, one of the treatment group members, demonstrated a higher
intensity of contraction for the hamstrings when compared to the quadriceps under the
unfatigued state. The prolonged activity of the hamstrings over the stance phase under
the fatigued condition indicated the subject’s reliability on the hamstrings group to assist
in knee stability. During the fatigued state, the hamstrings were active over the first half
of the stance phase, and during the swing phase. However, the intensity of contraction
demonstrated by the hamstrings was lower than that of the quadriceps group.
Characteristics presented in the linear motion of the lower extremity joints were
similar for all subjects tested in the study. Adaptations in the linear displacements were

directly related to adaptations observed in the angular motion. Limited extension at the

104

knee joint during the stance phase was related to slower horizontal displacement of the
knee joint, while differences in the slopes of the joint displacements were related to
changes in the angular displacement patterns, under both tested conditions. The velocity
and acceleration magnitudes were smaller for the treatment group than for the control
group under the unfatigued condition. Finally, both groups demonstrated a decrease in
the velocity and acceleration magnitudes during the fatigued state when compared to the
unfatigued state.

Both groups in this study demonstrated similar gait patterns under both tested
conditions. However, differences in range and timing were found to be characteristic
adaptations under the fatigued state. Greater variability in the gait patterns seemed
characteristic of the fatigued condition. Both groups experienced greater magnitudes in
the angular velocity and acceleration values at the knee joint, under the fatigued
condition than for the unfatigued condition. These higher velocity and acceleration
magnitudes are known to increase the stresses on soft tissue in the joint. Ifthe mechanics
of the joint are not fully restored after an injury, these increases in magnitude can result
in reinjury. Joint stability provided by muscular contraction was compromised during the
fatigued condition, as was shown by changes in EMG patterns under a lower magnitude
of contraction. Therefore, adaptations in the knee kinematics during gait under the
fatigued condition are of greater concern for the injured subject than for the uninjured

subjects, due to the restricted ability of the ligament to stabilize the knee joint

CHAPTER V

CONCLUSIONS

The role of the anterior cruciate ligament (ACL) as primary stabilizer of the knee
joint has been recognized by several authors (Jackson et al., 1987; Schipplein et al.,
1991). When an injury to the ACL occurs, the knee joint’s stability is compromised.
Strengthening of the thigh muscles has been shown to restore some level of stability to
the ACL-deficient knee joint (Schipplein et al., 1991). Gait analysis has been widely used
in an attempt to recognize adaptations of gait pattern caused by injuries to the ACL
(Andriacchi, 1990; Andriacchi, 1993; Timoney et al., 1993; Berchuck et al., 1990).
Quadriceps avoidance gait has been identified in subjects with ACL deficient and
reconstructed knees (Berchuck et al., 1990). This adaptation is characterized by a
reduction in the knee flexion angle during the initial 20% of the gait cycle. Although
kinematic and electromyographic research has been conducted to analyze the muscular
activity patterns presented by individuals with ACL reconstruction during walking
(Shiavi et al., 1992), there have been no studies reported to analyze the influence of
lower extremity muscular fatigue on gait characteristics of ACL reconstructed, or ACL
deficient individuals. It is a widely accepted fact that muscle fatigue can jeopardize the

level of joint stability during movement (Dul et al.,1984).

105

106
Research on the effects of muscular fatigue during gait for individuals with ACL

reconstruction is necessary to understand the implications for athletes’ reintegration into
practice. The effects of muscle fatigue on knee joint stability may be detrimental to
athletes returning to practice and competition, prior to full restoration of normal knee
mechanics. Determination of adaptations in gait characteristics can be useful to the
athletic trainers, athletes, and coaches in the decision making process of when to return
the athlete to the field.

A three-dimensional analysis of gait characteristics of individuals with ACL
reconstruction and uninjured individuals was performed under unfatigued and fatigued
conditions. The purpose of the study was to determine what, if any, changes in gait
characteristics occurred due to lower extremity muscular fatigue. In addition, EMG was
used to investigate the relative sequencing of firing of the quadriceps and hamstrings
muscle groups. No asymmetries were found in bilateral segment lengths for each subject,
when measured anthropometrically. Cybex results for the ACL reconstructed group
showed the accepted three to two ratio of the hamstrings to quadriceps muscle strength.
In addition, strength differences lower than 15 percent between left and right sides for
both quadriceps and hamstrings groups were found. This is the maximum strength
difference accepted by the NATA prior to reintegration of the athlete to practice. All
subjects had laxity tests within the +/- 1 normal range. A control group was tested under
unfatigued and fatigued conditions to determine if possible differences presented by the

ACL reconstruction group were also exhibited by uninjured individuals.

107

The three-dimensional analysis examined the knee joint’s linear and angular
motion during a full gait cycle. Kinematic data were collected on three control subjects,
and two subjects with bilateral ACL reconstruction. All subjects performed three trials
under unfatigued and fatigued conditions. A bicycle ergometer submaximal test was
utilized to fatigue each subject. A 75 watts work load was used initially; with a 25 watts
increaes every 2 minutes. The Borg scale was used to rate the level of fatigue every 2
minutes. After each walking trial, the subjects were asked to rank their level of fatigue on
the Borg scale. If the results dropped more than two points on the scale the subjects were
asked to repeat the bicycle ergometer test. Two trials under each condition were digitized
as part of the analysis. The calculations of linear and angular kinematics were performed
only on the side of the most recent injury for the treatment group, and the side closer to
the cameras for the control group. Linear and angular parameters were described for each
group under the unfatigued and fatigued conditions. The results of the two groups were

summarized to identify any trends observed during the analysis.

I. LIMITATIONS

The following limitations of the study must be taken into consideration before
generalizing the results. First, the low number of subjects and the characteristics of the
data collected did not allow for statistical comparisons of the results. The results of the
study were reported in a descriptive manner, without statistical conclusions. Second,
some limitations were experienced due to the inability of the software to accurately

calculate transverse rotations at the knee joint. Internal/extemal rotation data were not

108
reported due to the magnitude of the error presented in the results. The kinematic

analysis was performed only on flexion/extension and abduction/adduction movements.
Third, during the test under the fatigued condition, the same level of fatigued was
assumed throughout the three trials. The maintenance of fatigue was difficult to regulate,
as each subject was asked to perform three trials. However, the level of muscle fatigue
might have been jeopardized by unexpected delays, such as markers falling off, or system
failures. The use of the Borg scale assisted in identifying the perceived fatigue of each
subject. A better system to quantify muscular fatigue might be needed if the same level

of fatigue is to be maintained throughout trials.

II. HYPOTI-IESES

Three hypotheses were tested for this study. The first hypothesis stated that
individuals with ACL reconstruction would exhibit greater muscular activity during the
stance phase under unfatigued conditions than the normal subjects. Because of problems
experienced with EMG data collection for Subject 5, the examination of this hypothesis
was based solely on the results presented by Subject 4 and is therefore limited in scope.
During the stance phase of the unfatigued condition, Subject 4 presented greater
muscular activity than the subjects in the control group. The hamstrings and quadriceps
were active over a longer period of the stance phase, when compared to the muscle
activity presented by both the control group and the expected normal under the
unfatigued condition. During the unfatigued condition, Subject 4 showed hamstrings

activity from foot contact to 55% of the cycle, in the first trial; and from 10% to 90% of

109
the gait cycle during the second trial. Normal muscular activity by the hamstrings is

expected for the initial 15% of the cycle, and from 7 5% to completion of the cycle. The
quadriceps were active from 10% to 55% of stance and then again from 60% to
completion of the cycle for the first trial of Subject 4. During the second trial, the
quadriceps were active for the initial 30% of the gait cycle. The expected activity pattern
of the quadriceps during the stance phase, has muscle activity for the initial 25% of the
cycle, from 50% to 60% of the cycle, and then again for the last 5% of the cycle. The
results of this study supported the first hypothesis.

The second hypothesis stated that individuals in the ACL-reconstruction group
would demonstrate lower linear and angular parameters at the knee joint during the
fatigued state, when compared to the unfatigued condition. Linear and angular
displacements, velocities, and accelerations were shown to be lower in magnitude for
portions of the stance and swing phases of the gait cycle under the fatigued condition.
Angular velocities and accelerations for flexion/extension under the fatigued condition,
were higher than those presented under the unfatigued condition. Angular velocities and
acceleration for abduction/adduction were lower for both subjects in the treatment group
under the fatigued condition, when compared to the unfatigued condition. The
differences found in the gait patterns were not due solely to overall lower magnitudes
presented at the knee joint. Therefore, this hypothesis was not supported by the results of
the study.

The third and last hypothesis was not supported by the subjects forming the ACL-

reconstruction group. The hypothesis stated that the subjects with ACL reconstruction

l 10
would experience adaptations of greater magnitudes at the knee joint under the fatigued

state than the control group. Changes in gait characteristics were found for all subjects in
the study. Adaptations presented by the subjects in the treatment group were of the same
magnitude as those presented by the control group, between the two tested conditions. A
greater flexion/extension range of motion at the knee joint was seen under the fatigued
condition for the treatment group. However, all subjects in the study demonstrated the
same relative change in range of motion. Adaptations seen under the fatigued condition
in abduction/adduction angular displacement were different for all subjects. Due to the
variability in adaptations presented by all the subjects, the magnitude of changes cannot
be quantified in group comparisons.

Timing differences in linear displacements were experienced by both groups
under the fatigued condition, when compared to their respective unfatigued condition.
Adaptations presented under the fatigued condition by the treatment group, were
comparable in magnitude to those experienced by the control group. Both groups showed

similar displacement patterns under both conditions.

III. SUGGESTIONS FOR FUTURE STUDIES

Further research in this area is recommended. Recommendations for future
studies will be made based on necessary changes in order to obtain better quality of
results. Due to the system’s limitations, the subjects should be targeted using a triad
system (see Figure 51). This targeting style would allow the system to identify a

coordinate system about the joint, and therefore be able to calculate rotations about the

11 1
three axes of rotations. A primarily sagittal targeting style only allows for calculations of

rotations in the sagittal and frontal planes.

 

 

Figure 51: Placement of Targets Using Triads.

The problem of target blocking might be reduced by adding a third camera on the
same side as the other two cameras (see Figure 52). Accurate digitization of the hip target
was difficult due to consistent target blocking caused by the arm swing during the trials.
Adding a third camera might increase the number of frames in which the hip target is
seen by at least two cameras, and therefore increase the accuracy of digitization of this

target.

a a a

. . .
O L
v
v - .
a A ‘.
.’ . '
u a
e I
, e
e . -.
a . .
o e
.n 0 ~—
- . .
’ .
I .
, n
e , e
n .
j a . -.
0‘: :

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.

. b

Figure 52: Suggested Testing Setting Using Three Cameras

 

Range of motion of both injured and uninjured knees should be measured as part
of the pre-test administered to all subjects. This measurement would allow detection of
limitations in range of motion that later might be exhibited during gait. Normal range of
motion and strength testing results would allow the investigator to discard these two
factors as the causes of any adaptations seen in gait.

The maintenance of fatigue was difficult to ensure, since the subjects were asked
to perform three walking trials. To assist in maintaining fatigue, the Borg scale was used.
A different fatiguing protocol might be used to more closely resemble the type of muscle
fatigue experienced after an athletic practice. Bilateral muscular activity, as well as
kinematic data, might be needed to understand any compensatory actions that might
occur due to the fatiguing of the muscles of the lower extremity. Forces and moments are
important kinetic parameters for determining gait abnormalities. A complete study which
includes kinematic, kinetic, and electromyographic data might be of greater value to

determine the overall changes that occur due to lower extremity muscular fatigue.

LIST OF REFERENCES

LIST OF REFERENCES

Andriacchi, T. (1990). Dynamics of pathological motion: applied to the anterior
cruciate deficient knee. Journal of Biomechanics 23 99-105.

 

Andriacchi, T. (1993). Functional analysis of pre and post-knee surgery: Total

knee arthroplasty and ACL reconstruction. 10mg of Biomechanical Engm' eering, 115,
575-5 8 1 .

Angeli, C. (1995). User’s guide to the Ariel Performance Analysis System.
Unpublished manuscript.

Arms, S., Pope, M., Johnson, R, Fischer, R, Arvidsson, 1., & Eriksson, E.
(1984). The biomechanics of ACL rehabilitation and reconstruction. The Amerim
Journal of Sport Medicine, 12, 8-18.

Aune, A., Nordsletten, L., Skjeldal, S., Madsen, J ., & Ekeland, A. (1995).
Hamstrings and gastrocnemious co-contraction protects the anterior cruciate ligament
against failure: An in vivo study in the rat. Journal of o aedic Researc 13 147-
150.

Basmajian, J., & DeLuca, J. (1985). Muscle: Alive. Their Functions Revealed by
Electromyography. Baltimore: The Williams and Wilkins Company.

Berchuck, M., Andriacchi, T., Bach, B., & Reider, B. (1990). Gait adaptations be
patients who have a deficient anterior cruciate ligament. The Journal of Bone and Joint

Surgery, 72-5, 871-877.

Borg, G. (1982). Psychophysical bases of perceived exertion. Medicine and
Science in Spogs and Exercise, 14, 377-381.

Ciccotti, M., Kerlan, R, Perry, 1., & Pink, M. (1994a). An electromyographic
analysis of the knee during functional activities. I. The normal profile. The American
Journal of Sports Medicine, 22, 645-650.

113

114

Ciccotti, M., Kerlan, R, Perry, J ., Pink, M. (1994b). An electromyographic
analysis of the knee during functional activities. H. The anterior cruciate ligament-

deficient and reconstructed profiles. The American Journal of Sports Medicine, 22, 651-
658.

Draganich, L., Jaeger, R, & Kralj, R (1989). Coactivation of the hamstrings and

quadriceps during extension of the knee. Journal of Bone and Joint Surgery, 71-5, 1075-
1081.

Dul, J ., Johnson, G., Shiavi, R, & Townsend, M. (1984). Muscular synergism -
II. A minimum-fatigue criterion for load sharing between synergistic muscles. Jopmal of
Biomechanics 17 675-684.

 

Feagin, J. (1988). The crucial ligaments. New York: Churchill Livingstone.

Gerdle, B., & Karlsson, S. (1994). The Mean frequency of the EMG of the knee
extensors is torque dependent both in the unfatigue and the fatigued states. Clinical

Physiology, 14, 419-432.

Gray, H. (1974). Gray’s angtpmy. Philadelphia: Running Press.

Guidelines for exercise testing and prescription. American College of Spprts
Medicine. (4th edition). (1991). Philadelphia, PA: Lea & Febiger.

Harris, G., & Wertsch, J. (1994). Procedures for gait analysis. Archives of
Physical Medical Rehabilitation, 75, 216-225.

Hirokawa, S., Solomonow, M., Lu, Y., Lou, Z., & D’Ambrosia, R (1992).
Anterior-posterior and rotational displacement of the tibia elicited by quadriceps

contraction. The American Journal pf Sports Medicine, 20, 299-306.

Jackson, D. & Drez, D. (1987). The anterior cruciate deficient knee. New
concepts in ligament repair. St. Louis: Mosby Company.

Lohman, T., Roche, A., & Martorell, R (1988). Anthropometric standardization
reference manual. Champaign, IL: Human Kinetics Books.

Macnicol, M. (1986). The problem knee - Diagposis and manggement in the
younger pat_ient. Rockville: Aspen Publishers.

Maquet, P. (1984). Biomechanics of the knee. Berlin: Springer-Verlag.

McNair, P., & Wood, G. (1993). Frequency analysis of the EMG from the
quadriceps of anterior cruciate ligament deficient individuals. Electromypgpaphy and

Clinical Neurophysiology, 33, 43-48.

115

Nicholas, J. & Hershman, E. (1995). The lower extremng and spine in smrts
medicine Vol. 2. St. Louis: Mosby.

Noyes, F ., Torvik, P., Hyde, W., & DeLucas, J. (1976). Biomechanics of
ligament failure. The Journal of Bone and Joint Surgeg, 56-; 1406-1418.

O’Connor, J. (1993). Can muscle co-contraction protect knee ligaments after

injury or repair? Journal of Bone and Joint Surgeg, 75-B, 41-48.

Pecina, M. & Bojanic, I. (1993). Overuse injuries of the musculoskeletal system.
Boca Raton: CRC Press.

Peltier, R. (1985). Effects of semi-rigid orthotics on gbduction-addpction
moments at the knee joint during walking. Unpublished master’s thesis, Michigan State
University, Lansing.

Renstrom, P., Arms, S., Stanwyck, T., Johnson, R, & Pope, M. (1986). Strain
within the anterior cruciate ligament during hamstring and quadriceps activity. fl;
American Journal of Sports Medicine, 14, 83-87.

Schipplein, O., & Andriacchi, T. (1991). Interaction between active and passive
knee stabilizers during level walking. Journal of Orthopaedic Research, 9, 113-119.

Shiavi R, Zhang L., Limbird T., & Edmondstone M. (1992). Pattern analysis of
electromyographic linear envelopes exhibited by subjects with uninjured and injured
knees during free and fast walking. Journal of Orthopaedic Research 10, 226-236.

Solomonow, M., Baratta, R, Zhou, H., Shoji, H., Bose, W., Beclg C., &
D’Ambrosia, R (1987) The synergistic action of the anterior cruciate ligament and thigh

muscles in maintaining joint stability. The American Journal pf Sports Medicine, 15,
207-213.

Tibone, J ., Antich, T., Fanton, G., Moynes, D., & Perry, J. (1986). Functional
analysis of anterior cruciate ligament instability. The American Journal of Smrts
Medicine 14 276-284.

 

Timoney, J., Inman, W., Quesada, P., Sharkey, P., Barrack, R, Skinner, H., &
Alexander, H. (1993). Return to normal gait patterns after anterior cruciate ligament
reconstruction. The American Journal of Sports Medicine, 21, 887-889.

Valmassy, R. (1995). Clinical biomechanics of the lower extremities. Boston:
Mosby.

116

Winter, D. (1980). Overall principle of lower limb support during stance phase of
gait. Journal of Biomechanics 13 923-927.

 

Yack, H., Riley, L., Whieldon, T. (1994). Anterior tibial translation during
progressive loading of the ACL-deficient knee during weight-bearing and nonweight-
bearing isometric exercise. Journal of Orthopaedic Sports Physical Therapy, 20, 247-253.

Zatsiorky, V., Werner, S., & Kaimin, M. (1994). Basic kinematics of walking.
The Journal of Sports Medicine and Physical Fitness, 34, 109-131.

APPENDICES

APPENDIX A

117
APPENDD( A1

Informed Consent Form

Subject’s Name:

 

The present study will consist of a biomechanical evaluation of gait
characteristics of a group of individuals without injury to the lower extremity, and a
group with anterior cruciate ligament reconstruction. On the test day prior to the
initiation of testing, anthropometric measurements of the lower extremity will be taken.
Knee joint laxity will be tested by a certified athletic trainer, the Lachman test will be
used for this purpose. I will be asked to complete an information sheet. I understand that
both groups will follow the same testing protocol. I understand that I will be asked to
walk along a walkway while being filmed, and electromyographic activity (muscle
activity) will be recorded. Following a set of three trials, I will be asked to ride a bicycle
ergometer until the onset of muscle fatigue as determined by the Borg scale and EMG
activity. Another set of three trials will be filmed, after the onset of fatigue.

I understand that all testing will only require a single day commitment of
approximately three hours. I understand that in case of equipment failure I may be asked
to return another day to complete testing.

I understand that participation in this study is voluntary, and that I am free to
withdraw during any portion of the study without penalty. I understand all results will be
treated with strictest confidence and I will remain anonymous in any report of research
findings; on request and within these restrictions results may be made available to me.

I understand that if I am injured as a result of my participation in this research
project, Michigan State University will provide emergency medical care if necessary. I
further understand that if the injury is not caused by the negligence of MSU, I am
personally responsible for the expense of this emergency care and any other medical
expenses incurred as a result of this injury.

Signed: Date:

 

Address:

 

Telephone Number: ( )

 

PRINCIPAL INVESTIGATOR: Claudia A. Angeli
(517) 353-0728 / (517) 351-7124

FACULTY ADVISOR: V. Dianne Ulibarri, PhD.

118

APPENDD( A2

Informed Consent Form

Subject’s Name:

 

I understand that I am being considered as a subject in the anterior cruciate
ligament reconstruction group for a biomechanical evaluation of gait characteristics of a
group of individuals without injury to the lower extremity, and a group with anterior
cruciate ligament reconstruction. I understand that I will need to be Cybex tested. The
cybex test is for subject recruitment purposes only. If selected as a subject I understand
that I will need to return on a designated day to participate in the study which has been
explained to me. At the time, I will sign a second consent form, dealing specifically with
the testing protocol.

I understand that participation in this study is voluntary, and that I am free to
withdraw during any portion of the study without penalty. I understand all results will be
treated with strictest confidence and I will remain anonymous in any report of research
findings; on request and within these restrictions results may be made available to me.

I understand that if I am injured as a result of my participation in this research
project, Michigan State University will provide emergency medical care if necessary. I
further understand that if the injury is not caused by the negligence of MSU, I am
personally responsible for the expense of this emergency care and any other medical
expenses incurred as a result of this injury.

Signed: Date:

 

Address:

 

Telephone Number: ( )

 

PRINCIPAL INVESTIGATOR: Claudia A. Angeli
(517) 353-0728 / (517) 351-7124

FACULTY ADVISOR: V. Dianne Ulibarri, PhD.

APPENDIX B

1 19
APPENDIX B

Anthropometric Data Sheet

Subject’s Name: Code:

Group:

 

Dominant side: Right Left (kicking leg) Measurements: cm.

in.

Standing Height: Weight: kg lb

 

Measurement Right Left

 

Leg length

 

Upper thigh girth

 

Calf girth

 

 

Femur breadth

 

 

 

 

Recorder:

 

Measured by:

 

APPENDIX C

120
APPENDIX C

F atiguing Protocol

The submaximal bicycle ergometer test described in the American College of
Sports Medicine guidelines (1991) for exercise testing and prescription were followed.

The test consisted of two minute stages, in which resistance was increased by 25
watts. The revolutions per minute (RPM) was set at 75. The resistance continued to be
increased until the onset of fatigue.

STAGE I: minutes 1-2

Work load in watts: 75 Work load in kg/m/min.: 450

STAGE H: minutes 3-4

Work load in watts: 100 Work load in kg/m/min: 600

STAGE IH: minutes 5-6

Work load in watts: 125 Work load in kg/m/min.: 750

STAGE IV: minutes 7-8

Work load in watts: 150 Work load in kg/m/min.: 900

The subjects were asked to concentrate on only rating their feeling of muscular
fatigue and were told that 10 in the rating of perceived exertion (RPE) scale meant
extreme muscular fatigue. Testing was stopped after the onset of fatigue and a perceived
exertion and level of fatigue of 8 in the Borg scale.

The RPE scale described in Borg (1982) was used in this study.

121
Category RPE Scale

0 Nothing at all
0.5 Very, very weak
1 Very weak

2 Weak

3 Moderate

4 Somewhat strong
5 Strong
6

7 Very strong

10 Very, very strong

* Maximal

APPENDIX D

122
APPENDIX D

User’s Guide to the Ariel Performance Analysis System

The grabbing and digitizing sections of APAS user’s guide (Angeli, 1995), will
be presented here.

GETTING STARTED

 

 

APAS Main Menu:
* Grab

* Digitize

* Transform

* Smooth

* View

* Graph

* Print

* Kinetics

* Analog

* Tree

 

 

A. Grab
(directory -- OK)

 

FRAME_GRABBING MAIN MENU

Filename Capture Restore Delete VCR TimeCodes
Exit

(1) (2) (3) (4) (5) (6)
(7)

 

 

 

123

(1) New Old Close Quit

Root filename:

 

Enter a name which will help you identify the trial and the camera. Each videotape

(camera view) for each trial will require a different filename.

The top part of the screen will display the filename, plus other information. From this
information only one number will be important to you at this time. The image capacity
(flames) is the available space in memory to store images. In the next step you will go
over the videotape and pick the images that you want to grab, and later digitize. Check
that this number does no exceed the memory limit, take into consideration the skip
factor, (explained later). Ifthe number of images you plan to grab, is over the memory
capacity, stop and call for help!

-- M: the available memory to store images will decrease each time images in a new
file are grabbed.

(5) Play Stop Rew. Fwd. Pause

For this step is more convenient to use the VCR directly. For the slow motion
control, you need to press play and search at the same time. When the white dash mark in
the knob is on still the image will freeze.

Find the first frame of movement or the point which is going to determine the
synchronization of both cameras. This is going to be critical during the transformation
process to assure the correct correlation of the images. Once you find that point reset the
counter, which appears on the top of the screen, by pressing F3.

Move forward, using the search knob, until the “end” of the activity, (you decide
when you have seen enough). The field counter is going to indicate the number of frames

for the activity. Remember this number it is going—to become very important for future

 

use. I recommend you write this number down, along with the filename, (take it from

experience). Appendix A contains an example of a data sheet that can be used.

124

Rewind the tape so the counter is at 0 again, (first frame), use the searching knob.

F10 -- will take you back to the main menu.

 

 

(2) Capture menu
Control Data VCR Params Toggle Confirm Quit
(a) (b) (C) (d) (e) (f) (g)

 

(d) Params menu

 

ENTER PARAMETERS FOR GRABBING IMAGES
File description: VCR: Auto
First image offset: 0 # saved frames: Skip factor: _

 

 

 

Under file description enter useful information such as, subject’s name, camera
ID, trial number, etc. This information will appear on t0p of the screen during the
digitizing process, allowing you to check that you have called the correct file.

Leave the VCR option in Auto. During the grabbing process, the computer will
control the VCR, in terms of the frames to be saved. If the option is changed to
manual, you will have to select frame by frame the ones to be saved.

The next entry, first image offset, is one that you do not have to worry about. Of
course the key to this option was rewinding the tape back to the 0 point after
counting the frames.

# of saved fiames refers to the number of frames that you want to save in
memory. Here is when the number in the field counter, that hopefully you wrote
down (and you can find that paper), becomes important. To calculate the number

of saved frames, first you need to decide if you want to grab all the frames in the

 

125
sequence from the starting point to the end point. This is going to depend on the

speed of the activity. The number you need to input under this option is going to
be equal to the number of frames (the number you wrote down), divided by the
skip factor + 1.

The skip factor is equal to the number you want to skip in between grabbed
frames, (very self explanatory). As mention above, if you are analyzing a very
slow activity, it may not be necessary to digitize every frame. A skip factor of 1
will grab every other frame, reducing your number of frames by half.

* * Make sure you press entergier each entry, otherwise your entries will not be
saved and the default value will be taken. **
F10 - After all options have been entered, return to the previous menu.

(b) The grabbing process begins.

After all the specified frames have been grabbed, the computer returns to the
previous menu, (capture menu). At this point rewind the tape to the calibration structure
image (make sure it is from the same camera view as the grabbed images). When you
have that image on the monitor you are ready to grab the control frame.

(a) When you highlight the Control option and press enter, it automatically grabs the
image of the control frame; actually it grabs the image that is on the monitor at that time.

(g) Quit out of the capture menu.

At this point you are finished with the grabbing process for one camera. Now you have
the option to start digitizing the images for this view, or you can go ahead and grab the
images from the other view(s).

As you start the grabbing process for the rest of the views, use a different filename for
each. To start digitizing, after grabbing one or all the camera views, exit out of the main
menu (F10). The main APAS menu will appear on the screen, and you will be ready to
start digitizing, (here is the fun part! ! l).

126

B. Digitize
(Directory -- OK)

 

New Old Calibrate Exit

 

 

 

New - set up a sequence. This sequence is going to be the same for a_lI the camera
views. Give the sequence a name, it needs to be different from the filename used in

the grabbing module.

 

Enter Sequence information

File description:

 

Type: System Units: cm Filming date:
Height: Weight:
# points: #Control points:

 

 

 

File description allows up to 30 characters. Remember this is for the sequence
information, were all the views are going to be combined.

In the We option, use the M defined points.

Under units choose the ones that were used to measure the calibration structure.
I do not think that filming date needs any explanation.

Height and weight refer to the subject.

Under number of points, type how many points you want to digitize per frame. It

should correspond to the number of joint markers placed on the subject.

 

127
The control points refer to the number of points to be digitized in the calibration

Stl'UCtLll’C.

Press F10 when all the information has been entered.

 

SELECT POINT ID SOURCE:
File Keyboard

 

 

 

The file option will allow you to use points already defined in a previous file. This is
used when you are going through the digitization process for the another trial or
subject, you conveniently call on the points from the first view, instead of entering
each point again. Find the sequence name from which you want to copy the points.
For the first view of the first trial, press enter on keyboard. This will allow you to
select the points you want to digitize.

The color monitor is going to display a list from which you can choose the joints for
digitization, (point [D definitions). Fill in the point identifiers with the two-letter
code, in the small screen. The sequence that is used is vegy important. The computer
will later use the same sequence during digitization and connection of points.

After all the points have been identified press F10.

The computer is ready to call on the grabbed images. From the screen select the
filename of the grabbed images, (make sure it is the correct camera View; specially if
you are digitizing the second view).

The color monitor is going to display the first frame from the saved images. The
small screen will ask for a sample figure. This frame is going to be digitized for the
purpose of point connection, so it is important that all the points are visible, to
provide greater accuracy in your sample. If the first image is not representative of all
the points, you can advance the frames with the F1 key until you find the “best

frame” for the sample. To select the image press enter. Then press F10.

128

The small screen is going to display a connection table, while the color monitor is
going to display the sample frame. On the top of the connection table, the computer is
going to indicate the joint to be digitized. With the mouse place the + on top of the
joint marker, (middle of the marker), and press the left button to mark it. A number is
going to appear beside the marked joint, indicating the identification of the joint.
Press F1 to advance to the next joint. After all the joints have been marked press F10.

 

CONTROL POINT LOCATION SOURCE
File Keyboard

 

 

 

Select keyboard for the first view of your first trial. Again, as with the point
identification, for subsequent trials and subjects you can select file.

The control point location table will appear on the screen. Enter the location of the
points, from the calibration structure measurements, in the order to be digitized.
Make sure the measurements are all in the same units. The system defines + x to the
right, + y up, and + 2 coming out of the screen.

Press F10 after entering all points.

 

SELECT SEQUENCE OPTION
New view Old view Points Control pts Seq-info Quit

 

 

 

Select new view for each camera view. If you used only two cameras during filming,
each sequence name should end up having two views.

A screen asking for information about each view will appear on the small monitor.
Use relevant words which will later help you identify the images. Press F10 when

done.

 

SELECT DIGITIZER TYPE
Grabbed_video Live_video External Joystick Quit

 

 

 

129

Grabbed_video will call on the file that has the saved video images. Select the
appropriate filename from the list provided, (keep in mind the camera view). The
small monitor will show you the file’s information, confirm your choice by pressing
Mex.

The first frame will appear on the color monitor, and a set of commands will appear
on the small monitor.

A fixed point must be digitized first for each frame. The computer will indicate the
joint to be digitized on the top of the screen. As you mark each body joint, you will
see the connection line, which will create the stick figure. If you need to correct a
marked joint press F3 and the last digitized point will be erased. After marking all

the points in the frame press F1 to advance to the next frame.

a few hours later, when all the frames have been digitized, press F9 to digitize the

control frame.

 

SELECT DIGITIZING OPTION
Control Synch Point Time Update_clock Bell Frame # Quit

 

 

 

Select Control.

 

SELECT CONTROL POINT OPTION
Digitize View Read Quit

 

 

 

Select Digitize.
Again the first point to be digitized is the fixed point. Then digitize the points in the
calibration structure in the same order as the locations were entered.

Press Fl after _a_l_l the points have been digitized.
Highlight Quit.

130

If you are digitizing your second trial or subject, then you can use the previously
digitized calibration structure. Go to Read, and find the sequence name that has
already been digitized, the extension on the sequence name will indicate the view.
Agian make sure you call the right view. After your selection, the calibration
structure frame will come up on the screen, and it will include the digitized points;
this is a good time to check if you called the correct view.

Press F10 twice to exit out of the menus.

At this point you can go ahead and digitize the second view, (if you have already
grabbed the images). To digitize the second view, select Old from the sequence
menu. After you pick the sequence name from the list repeat the same process.

If you have to go back to grab the images for the second view, press F10 one more

time, and then enter Yes.

APPENDIX E

13 1
APPENDIX E

Subject’s Data Sheet

 

 

 

 

 

 

ACL injured group
Subject’s Name: Code:
Address:
Telephone: ( )
Date of birth (m/d/y):
Dominant side: right left
Injured knee: right left
1. Approximate date of injury (m/y):
2. Have you had ACL reconstruction: Yes No If yes, when? (m/y):

 

3. Approximate duration of rehabilitation after surgery (in months):

 

 

 

4. Did you play any sports prior to the injury? Yes No
If yes, list:
Level: recreational college professional
Frequency (times per week):
5. Did you resume the same sport after rehabilitation of the injury? Yes No

If your answer is no, please explain why?

 

 

132

6. Are you physically active? Yes No
6a. How would you rate your present exercise intensity compared with your level
prior to the injury?
very low low same high very high

6b. How long are your workouts? (in min.)

 

60. How many times a week do you exercise?
One Two Three More than three
7. Do you currently experience any pain in the injured knee while you exercise?

Yes No If yes, explain

 

8. Do you feel restricted by your injury when participating in physical activities?

Yes No If yes, explain how?

 

 

9. Were your every day activities affected as a consequence of your injury? Yes No

If yes, explain

 

 

133

Subject’s Data Sheet
Control group

Subject’s Name:

 

Address:

 

 

Telephone: ( )

 

Date of birth (m/d/y):

 

Dominant side: right left
1. Have you ever had any knee injuries? Yes

If yes, explain

No

Code:

 

2. Are you physically active? Yes No
recreational college sports
3. How many times a week do you exercise?
One Two Three
4. How would you rate you workout?
Very light Light Moderate

5. How long are your workouts? (in min.)

If yes, at what level:

professional sports
More than three
Intense Very intense

 

APPENDIX F

134
APPENDDI F

Angular Motion

Flexion/Extension and Abduction/Adduction angular displacements, velocities
and accelerations. The Figures represent two analyzed trials under each tested condition.
The first two trials under each condition were analyzed for all subjects. Subjects 1 - 3
formed part of the control group, while Subjects 4 and 5 were part of the ACL-
reconstructed group.

 

FleidenlExtenelonAngularDlephcenant
Subject 1 - F

 

 

 

o . r L
Y

T I j

0% . 20%

 

 

40% 60% 80% 1M
$Galt0yele

 

 

 

 

 

(0 00
Figure 1E: Knee Flexion/Extension Angular Displacement. Subject 1. (a) Unfatigued
Trials (b) Fatigued Trials.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FiexlonIEnenslonAngularDlsplacelmnt
Subjeth-UF

”'1 we.
70. — 1 70.
-60- “so
3:50.. " 50..
3;..- 2;..-
3330.. Egan.
20.. 20.
10 1°

0 : ‘r 0: r k a. 4 Pg‘

0% 20% 40% cost 80% 100% on m 40% 60% was 100%

VoGaitCyeie seanm
(0 0)

Figure 2E: Knee Flexion/Extension Angular Displacement. Subject 2. (a) Unfatigued
Trials (b) Fatigued Trials.

135

 

FiexlonIExtension Angular Displacement

 

 

 

 

 

 

 

 

 

 

Subject3-UF
80.. 80..
70._ L1 704
.533; 233‘
x ..
Egan Egan
3'30. 3'30.
20 20
10 c 10
0 0. t t : : 4
0% 20% 40% 00% 80% 100%
$Galt0yele
o)

 

Figure 3E: Knee Flexion/Extension Angular Displacement. Subject 3. (a) Unfatigued
Trials (b) Fatigued Trials.

 

 

 

   

 

 

 

 

 

 

 

FlexionIExtension Angular Displacennnt FlerdoniExtenelon Angular Dieplacennnt
subiecN-UF SubjectA-F
so so.
70 70.
:50 :60.
V50 50...
3;... 3;...
$330 5330..
20 20.
10 10
0 . i . Def—r : r . Q.
0% 20% was 60% acre 100% on 2095 4095 ems was 100%
SSGaItGyele some”.
(0 0)

Figure 4E: Knee Flexion/Extension Angular Displacement. Subject 4. (a) Unfatigued
Trials (b) Fatigued Trials.

 

  
 
  

 

 

 

 

 

 

 

 

 

 

FlexionlEnenslon Angular Displacement HeidenlExtenelen Angular Displacement
Subjects-0F Subjects-F
so, so,
70‘:TRIAL2 70‘:TRIAL4
-60- _00.
3:50.. . 50+ ragga
:g..- 51....
E2530“ £330., Midst-nee
”20.. 204
10.. 10,
0 r : : 0. i : : : i
oar. 20% 40% 60% 30% 100% 09s 20* 40$ 60% 30% 1009s
ate-em ass-now.
(0 0)

Figure 5E: Knee Flexion/Extension Angular Displacement. Subject 5. (a) Unfatigued
Trials (b) Fatigued Trials.

 

FiexionIExtenslon Angular Velocity
Subject 1- UP

 

_TfiAL-1

 

 

 

DEGREES!“

 

 

 

 

(a)

136

 

 

 

 

 

 

 

 

FieldonIExtensionAngularVeloclty
400 Subiect1-F
300 __TRiAL-4
8 200 “TRIAL-5
g 1CD c
K o _/__-2\ #4 fl, 4
Sam W 60% amt 100%
mm
.200 oeoif
.300 sconrrcvcte

Figure 6E: Knee Flexion/Extension Angular Velocity. Subject 1. (a) Unfatigued Trials

(b) Fatigued Trials.

 

FlexionIExtenslon Angular Velocity
Subject 2 - UF

__TRlAL-1

 

 

 

 

 

 

 

 

 

 

Wis-é???

 

 

 

 

 

 

100%

 

 

Figure 7E: Knee Flexion/Extension Angular Velocity. Subject 2. (a) Unfatigued Trials

 

 

 

 

 

 

 

 

 

(b) Fatigued Trials.
FlexionIExtenslon Angular Velocity
400 Subject 3 - UP
300 ‘m
......_rRlAl. -2
: 2°° [X
3 100
g o A , ,
§ .100 40% 60% 100%
Midstm
2°° oe or
eoo %GAl‘l' CYCLE
(a)

 

 

400
300
200
100
0
1(1)
2(1)
300

 

 

 

 

 

 

Figure 8E: Knee Flexion/Extension Angular Velocity. Subject 3. (a) Unfatigued Trials

(b) Fatigued Trials.

 

 

 

 

DEGREES/Se

 

Flexion/Extension Angular Velocity
Subject 4 -UF

400
m I ’
20° ”TRIAL - 2

c Midstence

100

0 .A

60% Isms 100%
PC
oeoii

 

-1CD
-2(D
«X1

'loGAIT CYCLE

137

 

 

DEGREES/Se

 

Flexion/Extension Angular Velocity
Subject 4 - F

_TR|AL - 4
._.....TRIAL - 5

 

(a)

(b)
Figure 9E: Knee F lexion/Extension Angular Velocity. Subject 4. (a) Unfatigued Trials
(b) Fatigued Trials.

 

 

DEGREES/u

Flexion/Extension Angular Velocity
Subject 5 - UF

_TR|AL - 1
“TRIAL — 2

    

400
31)
200
1CD

0
100
200
3D

 

 

 

DEGREES“.

Flexion/Extension Angular Velocity
Subject 5 - F

_TRIAL - 4
”TRIAL - 5
FC

   

 

(a) (b)
Figure 10E: Knee Flexion/Extension Angular Velocity. Subject 5. (a) Unfatigued Trials

 

   

   

    
 

(b) Fatigued Trials.
FieldonlExtension Angular FlexionIExtenslon Angular ’
4000.. Aceeleratlon-Subjectl-UF m Acceleration-Subject1-F
3000. — ”AL-1 3000 _TRlAL-4
m. -m... w m
‘3’ 10001 g 1013
a o- 3 0 .
E 40000. g .1000 100%
D .2000 -. O .2000 c
3000 “Fe m l
.2000 J. 5““le 4000 r ‘loGAlTC‘YCLE

 

 

 

 

 

(b)
Figure 11E: Knee Flexion/Extension Angular Acceleration. Subject 1. (a) Unfatigued
Trials (b) Fatigued Trials.

 

 

 

138

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FlexionIExtenslon Angular FlexionlExtension Angular
4000 Acceleradon-Subjeth-UF 4000 Aeoeleration-Subjeth-F
30001 _TR|AL-1 3000} _TRIAL-4
.m m
3 1000 E 1000 L
Fl ' 3
g o g o .
'6 40000 100% 3 100000.. / (swaths
g ,m FC g-m Mimtmce
.3000 PC 3000 l c
4000 i ‘AGAITCYCLE .4000- ‘ SSWCYCLE
(a) (b)
Figure 12E: Knee Flexion/Extension Angular Acceleration. Subject 2. (a) Unfatigued
Trials (b) Fatigued Trials.
Flexion/Extension Angular FlexionIExtenslon Angular
40001 Acceleration-Subject3-UF 4000 Acceleration-Subjecta-F
3‘3”“ mi
,m_ ..../ .33: ........
1W . el .1.
El 0 V \iF E /\
K K
e .10000..60% 100% e 1000 ‘ U89“
3' .2000 J/mm Midstance 3 .2000 40%/7,20% Midstame
.3000 .. L
4000 . 7.0m CYCLE .4000 r %GAITCYCLE
(a) (b)
Figure 13E: Knee Flexion/Extension Angular Acceleration. Subject 3. (a) Unfatigued
Trials (b) Fatigued Trials.
FlexionIExtenslon Angular FlerdonIExtenslon Angular
4000" Acceleration- ”Subjectl UP 4000 Acceleration-SubjectA-F
3000 . "—01- 1 3000 __1RIAL-4
m- am: /\\FC 2...
‘3’ 1000 .. § 1000
E 0 oeoil g 0 A : Toe oil ' . W.
‘5 MODE/A 20% M 80W100“ '0‘ .1000 20% V 80% 103%
’3 .2000 “re Midstance g .2000 Mldstance FC
S000 -. 3000 c
.4000 .L 'AGAIT ever: 4000 sent CYCLE

 

 

 

 

 

(a)

(b)
Figure 14E: Knee Flexion/Extension Angular Acceleration. Subject 4. (a) Unfatigued

Trials (b) Fatigued Trials.

 

 

 

139

 

Flexion/Extension Angular
Acceleration- -Subject5- UF

—__.1AL- 1
A.
_.TRIAL- 2 A
Toeofl' F
23%, m . j.

320)

 

 

 

 

 

 

 

 

 

 

 

g 0 §
Ill 0 r I“
§ 400006 20% M 60% 1 g .
g -2000 C Midstance E _
.3300 f "
4000 i 7.0101: circus 400° ,_ 5491‘" m
(a) (b)
Figure 15E: Knee Flexion/Extension Angular Acceleration. Subject 5. (a) Unfatigued
Trials (b) Fatigued Trials.
AbductionIAdduction Angular AbductionIAdductlon Angular

Displacement-SubjecH-UF

 

20 .— " 1
15 WTRIALZ
E
g 3 ‘0 Midstance Tonga
r»: 5 c
a: 0 \ l + : 1 W
3 o 60% 00% \was
40 FC
-15
%GaitCyele

 

 

 

Mimi-)Mbrue)

Degrees

Diaplacermnt-Subjecti-F

25

2°

15 :TRIAL4
C

Toeolf

M mums

 

_5 of/M 60%

40°;
-15

W

 

‘AGaltOyole

 

(a) (b
Figure 16E: Knee Abduction/Adduction Angular Displacement. Subject 1. (a)

Unfatigued Trials (b) Fatigued Trials.

 

 

AbductionIMductlon Angular
Displacement - Subject 2 - UF
25
20 _ -lAL1
15 .......rRlAL 2
Sr 10
ii 5
5' 1 Mldstance X
D g o 1‘ i 4 : i
a _5 40% f 80% 100%
-10 C Toe oil FC

%Galt Cycle

 

 

 

Degrees
Ada-VAN»)

AbductlenlAdductlen Angular
Displacement - Subject 2 - F

    
 
 

...__TRIAL4

  

Midsunce

SSGIKOyele

 

(a) (b)
Figure 17E: Knee Abduction/Adduction Angular Displacement. Subject 2. (a)

Unfatigued Trials (b) Fatigued Trials.

 

140

 

 

 

 

 

 

 

 

 

 

 

 

AbductionIAdduction Angular
flspiacermnt - Subject 3 - F

 

 

 

 

2: z
a: 35+.
8 3 3 3’
‘ ‘ : :
40% 60% 00% 1
$0.1! ml. fifilflm
(a) (b)

Figure 18E: Knee Abduction/Adduction Angular Displacement. Subject 3. (a)

Unfatigued Trials (b) Fatigued Trials.

 

  

 

      

 

 

 

 

 

 

 

 

 

AbductionlAdduction Angular WWW Angular
memorandum 0lspluconnnt-Subjoct4-F
25 25
20 _ 20 __
15 “mnl ,5 .......1RlAL4
7 10 ‘ - ‘0‘ FC
if 5 C Mmtance E 10 'l’oeot
i a PC fig 5 Midetance
a: o : £4? 0 4 f 117 :
”8 «5 100% 3 .5 0015 0011 100%
‘ -1o ‘ -10 c
-15 15
.20
ate-um 'LGeICyeie
(*0 (b)

Figure 19E: Knee Abduction/Adduction Angular Displacement. Subject 4. (a)

Unfatigued Trials (b) Fatigued Trials.

 

AbductionIAdduction Angular
Displacermnt - Subject 5 - UF

“TRIALZ'

Mitbtance

 

 

 

Ade-ylbdlfl
01

Degrees

$Galt°yele

 

  

 

Degrees

Adar-yawn;

 

 

 

 

 

(a)

(b)

Figure 20E: Knee Abduction/Adduction Angular Displacement. Subject 5. (a)

Unfatigued Trials (b) Fatigued Trials.

141

 

AbductionlAdductlon Angular Velocity AbductionIAdduction Angular Velocity
Subjecti-UF 35° Subjecti-F

200.. _TRIAL.1 200,
150 __ ..-.....TRlAL-2 150 . wTRw-‘E’

M idstance

  

DEGREES/Se
DEGREES!“
o

.150 ..
.200 .1 seem ever:

 

 

 

 

 

 

 

(a) (b)
Figure 21E: Knee Abduction/Adduction Angular Velocity. Subject 1. (a) Unfatigued
Trials (b) F atigued Trials.

 

 

 

AbductionIAdducflon Angular Velocity AbductionlAdduction Angular Velocity

250 Subjeth-UF Subjeth-F

200 —— ' “ ' ~ — j

-1 .. ___.....
g 100 : c S 100 .. fie
a 50 1F FC 3 50
g 0 T F 0 1 x A /<\\ = ,
iii .5000: 20% 40% 00% 100% § 50216 \W“ 109*
D -100 + Mldstance Toe or .100 ._ .

.15) l -150 .. Mmtmee de

-200 i -/.oArr ever: -200 -. %GAIT 0ch:

 

 

 

 

 

(a) (b)
Figure 22E: Knee Abduction/Adduction Angular Velocity. Subject 2. (a) Unfatigued
Trials (b) Fatigued Trials.

 

 

 

 

Abduction/Adduction Angular Velocity AbductionIAdduction Angular Velocity
Subjects-UP 25°. Subject3-F

 

 

 

 

 

 

 

 

(a) (b)
Figure 23E: Knee Abduction/Adduction Angular Velocity. Subject 3. (a) Unfatigued
Trials (b) Fatigued Trials.

 

AbductionlAdduction Angular Velocity
Subject 4 - UF

 

 

 

 

 

 

 

 

142

 

 

250...
200.
150.

 

AbductionIAdduction Angular Velocky
Subject 4 - F

 

_TfilAL-4

 

“TRIAL-5

 

 

 

 

(b)

Figure 24E: Knee Abduction/Adduction Angular Velocity. Subject 4. (a) Unfatigued

 

 

 

 

 

 

 

 

 

 

 

AbductionlAdductlon Angular Velocty

 

 

 

 

 

 

250 Subjects-F
200 _TRlAL-4
150 ”mm’5 m
8 10° ‘ FC
50 Toeoli
i o
g 20% 5096 100%
-100 PC Midetmce
.150
-200 amorous
(b)

Figure 25E: Knee Abduction/Adduction Angular Velocity. Subject 5. (a) Unfatigued

 

Trials (0) Fatigued Trials.
AbductionIAdduction Angular Velocity
250 Subject 5 - UP
200 jun -1
i
i
ii
a -
:2m %GAIT CYCLE
(a)
Trials (b) Fatigued Trials.
AbductionIAdduction Angular

Acceleration-Subjecti-UF

 

 

 

 

 

 

 

 

 

Figure 26E: Knee Abduction/Adduction Angular Acceleration. Subject 1. (a) Unfatigued

Trials (b) Fatigued Trials.

 

 

143

 

 

AbductionlAdduction Angular AbductionlAdduction Angular
4000 Acceleration - Subject 2 - UF

 

 

 

 

 

 

 

DEGRfiSIaec

 

 

 

 

 

 

 

 

(a)
Figure 27E: Knee Abduction/Adduction Angular Acceleration. Subject 2. (a) Unfatigued
Trials (b) Fatigued Trials.

 

 

AbductionlAdduction Angular AbductionlAdduction Angular
Acceleration - Subject 3 - F

Acceleration-Subject3-UF

FC

1%

  

DEGREESlaec
§§§§§o§§§

    
 

“TRIAL-5

 

  
 

 

 

$5“le

 

 

 

 

 

 

(b)
Figure 28E: Knee Abduction/Adduction Angular Acceleration. Subject 3. (a) Unfatigued

Trials (b) Fatigued Trials.

 

 

 

AbductionlAdductionAngular
Acceleration-Subject4-F

 

 

033%

 

 

 

 

 

 

 

 

(b)
Figure 29E: Knee Abduction/Adduction Angular Acceleration. Subject 4. (a) Unfatigued

Trials (b) Fatigued Trials.

 

DEGREES/sec

 

1500

ml

 

-1CX)O

AbductionlAdduction Angular
Acceleration - Subject 5 - UF

 

 

 

Midstance

acmm

 

 

(a)

144

 

 

AbductionlAdduction Angular
Acceleration - Subject 5 - F

 

 

1500
1000i
i so.
a PC Midstance Toeoil/\ FC
K J 1 L
o 0 . 'V . 4
g 0 20% 40% 60% 83% 100%
-5CD
-1(D0 'loGAlTCYCLE

Figure 30E: Knee Abduction/Adduction Angular Acceleration. Subject 5. (a) Unfatigued
Trials (b) F atigued Trials.