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THE EFFECTS OF DYNAMIC AND STATIC STRETCHING ON RANGE OF
MOTION AND PERFORMANCE

By

Katie M. Rapldng

A THESIS

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

MASTER OF SCIENCE
Kinesiology

2010

TABLE OF CONTENTS

List of Tables ....................................................................................................................... v
List of Figures .................................................................................................................... vi
Chapter 1
Introduction .......................................................................................................................... l
1.1 Overview of the Problem ........................................................................................... 1
1.2 Significance of the Problem ....................................................................................... 3
1.3. Purpose of the Study ................................................................................................. 7
1.4 Hypotheses ................................................................................................................. 8
1.5 Operational Definition of Terms ................................................................................ 8
Chapter 2
Review of Literature .......................................................................................................... 11
2.1 Overview of the Problem ......................................................................................... 11
2.2 Significance of the Problem ..................................................................................... 11
2.2.1 Bony Anatomy .................................................................................................. 12
2.2.2 Bony and Muscular Articulations ...................................................................... 13
2.2.3 Static Stabilizers ................................................................................................ 15
2.2.4 Dynamic Stabilizers .......................................................................................... 16
2.2.5 Range of Motion ................................................................................................ 18
2.3 Physiology of Stretching .......................................................................................... 19
2.4 Four Types of Stretching .......................................................................................... 21
2.5 Static Stretching ....................................................................................................... 24
2.5.1 Effect of Static Stretching on Range of Motion ................................................ 24
2.5.2 Effect of Static Stretching on Performance ....................................................... 27
2.6 Dynamic Stretching .................................................................................................. 30
2.6.1 Effect of Dynamic Stretching on Range of Motion .......................................... 30
2.6.2 Effect of Dynamic Stretching on Performance ................................................. 32
2.7 Conclusion ................................................................................................................ 36
Chapter 3
Methodology ...................................................................................................................... 37
3.1 Research Design ....................................................................................................... 37
3.2 Sample Population and Participant Selection ........................................................... 37
3.3 Instrumentation ......................................................................................................... 37
3.3.1 Goniometry ........................................................................................................ 37
3.3.2 Biodex System 3 Dynarnometer ........................................................................ 38
3.4 Static Stretching Intervention ................................................................................... 38
3.5 Dynamic Stretching Intervention ............................................................................. 41
3.6 Procedures ................................................................................................................ 43
3.6.1 Session 1 ............................................................................................................ 43
3.6.2 Session 2 ............................................................................................................ 45

iii

3.6.3 Statistical Analysis ............................................................................................ 45

Chapter 4
Results ................................................................................................................................ 46
4.1 Subject Demographics .............................................................................................. 46
4.2 Results for Shoulder Range of Motion and Peak Torque ......................................... 47
4.2.1 Shoulder Flexion ............................................................................................... 48
4.2.2 Shoulder Extension ............................................................................................ 49
4.2.3 Shoulder External Rotation ............................................................................... 50
4.2.4 Shoulder Internal Rotation ................................................................................ 51
4.2.5 Shoulder Peak Torque Away ............................................................................. 52
4.2.6 Shoulder Peak Torque Torwards ....................................................................... 53
Chapter 5
Discussion .......................................................................................................................... 55
5.1 Range of Motion at the Shoulder Complex Following Static and Dynamic
Stretching ....................................................................................................................... 55
5.2 Peak Torque at the Shoulder Complex Following Static and Dynamic Stretching .58
5.3 Utilization and Clinical Implications for Static and Dynamic Stretching ................ 60
5.4 Limitations of Current Study .................................................................................... 62
5.5 Future Research ........................................................................................................ 62
5.6 Conclusions .............................................................................................................. 63
Appendices
A. Health History Questionnaire .................................................................................... 66
B. Informed Consent Form ............................................................................................ 68
References .......................................................................................................................... 71

iv

LIST OF TABLES

Table
4.1 Player Positions for Baseball, Softball, and Volleyball ........................................... 47
4.2 Descriptive Statistics for F lexion Range of Motion for Stretching Conditions and
Testing Occasions .......................................................................................................... 48
4.3 AN OVA Comparing Stretching Conditions and Testing Conditions ...................... 49
4.4 Descriptive Statistics for Extension Range of Motion for Stretching Conditions and
Testing Occasions .......................................................................................................... 50
4.5 ANOVA Comparing Stretching Conditions and Testing Conditions ...................... 50
4.6 Descriptive Statistics for External Rotation Range of Motion for Stretching
Conditions and Testing Occasions ................................................................................. 51
4.7 ANOVA Comparing Stretching Conditions and Testing Conditions ...................... 51
4.8 Descriptive Statistics for Internal Rotation Range of Motion for Stretching
Conditions and Testing Occasions ................................................................................. 52
4.9 ANOVA Comparing Stretching Conditions and Testing Conditions ...................... 52
4.10 Descriptive Statistics for Peak Torque Away for Stretching Conditions and
Testing Occasions .......................................................................................................... 53
4.11 ANOVA Comparing Stretching Conditions and Testing Conditions .................... 53
4.12 Descriptive Statistics for Peak Torque Torwards for Stretching Conditions and
Testing Occasions .......................................................................................................... 54

4.13 ANOVA Comparing Stretching Conditions and Testing Conditions .................... 54

LIST OF FIGURES

Figure
1 Shoulder Stretching (static stretch 1) .......................................................................... 40
2 Shoulder and Triceps Stretch (static stretch 2) ............................................................ 4O
3 Biceps Stretch (static stretch 3) ................................................................................... 40
4 Sleeper Stretch (Posterior Capsule)(static stretch 4) ................................................... 4O
5 Shoulder Circles (dynamic stretch 1) .......................................................................... 42
6 Overhead/Down and Back Arm Swings (dynamic stretch 2) ..................................... 42
7 Side/Front Crossover Arm Swings (dynamic stretch 3) .............................................. 42
8 Wall Shoulder Girdle Stretch (dynamic stretch 4) ...................................................... 43

vi

CHAPTER 1

INTRODUCTION

1.1 OVERVIEW OF THE PROBLEM

Athletic trainers, physical therapists, and coaches are all faced with the dilemma
of which type of stretching is more effective - static or dynamic. This decision can be
difficult for any coach or clinician because the research is inconclusive. Several
researchers claim that static stretching is the key to increasing range of motion and
improving athletic performance (Kokkonen, Nelson, Eldredge, & Winchester, 2007)
while other researchers suggest that static stretching does not produce long enough
lasting gains in range of motion to really make an impact on one’s athletic performance
(DePino, Webright, & Arnold, 2000). Moreover, dynamic stretching is becoming
increasingly popular as recent research suggests dynamic stretching actively stretches and
warms the muscle tissue (Fredrick &Szymanski, 2001). To date, few researchers have
investigated if static or dynamic stretching is more effective in increasing range of
motion and peak torque at the shoulder complex.

Within the shoulder complex there are static and dynamic stabilizers, both which
play a large role in stretching and overall flexibility. The static stabilizers include the
labrurn, capsule, and ligaments. The glenoid labrum is a rim of fibrocartilaginous tissue
attached around the margin of the glenoid fossa (Peat, 1986). The labrum’s shape adapts
for the rotation of the humeral head, adding flexibility to the edges of the glenoid fossa
(Terry & Chopp, 2000). The joint capsule surrounds the joint as a whole and does not
contribute very much to the stability of the joint by itself. However, if the capsule is

stretched too far it can contribute to instability in the shoulder joint. Finally, the shoulder

ligaments allow for shoulder flexibility within the bony structures. The shoulder
ligaments also contribute to static stability within the complex.

The dynamic stabilizers include the four muscles of the rotator cuff, as well as
the deltoid and scapular stabilizers. The rotator cuff is made up of the supraspinatus,
infiaspinatus, teres minor, and subscapularis. These muscles act as the dynamic steering
mechanism for the humeral head. Due to the rotator cuff muscles being closer to the
center of rotation on which they act, they are able to provide stability to a dynamic
fulcrum during glenohumeral abduction (Terry & Chopp, 2000). These muscles can also
limit range of motion and decrease the amount of force available if they are not stretched
properly before activity.

Stretching is made possible due to numerous structures interacting with one
another. A combination of chemoreceptors, muscle spindles, and golgi tendon organs act
in unison to allow for the muscle to stretch without tearing. The chemoreceptors send a
message to the central nervous system, and then the golgi tendon organs provide the
central nervous system with feedback concerning the tension, while the muscle spindles
provide sensory information concerning the relative muscle length (Powers & Howley,
2004). When the muscle spindles detect the stretch of the muscle they send sensory
neurons to resist being stretched (Powers & Howley, 2004). When this takes place the
golgi tendon organs activate to allow for muscle relaxation. This is known as the golgi
tendon reflex (Saladin, 2004). These golgi tendon organs are the safety devices that help
moderate muscle contractions before it tears a tendon or pulls it loose from the muscle or

bone (Powers & Howley, 2004).

There are four ways to stretch: a) ballistic stretching, b) static stretching, c)
propioceptive neuromuscular facilitation (PNF) stretching, and (1) dynamic stretching
(Bandy & Irion, 1994). Ballistic stretching involves a bouncing movement where
repetitive contractions of an agonist muscle (prime mover) work to stretch an antagonist
muscle (a muscle that contracts with and limits the action of an agonist with which it is
paired) (Bandy & Irion, 1994). Static stretching involves slowly elongating the muscle to
tolerance (comfortably with no pain) and holding the position for an extended period of
time (Prentice, 2003). PNF is also known as contract-relax or hold-relax; these involve
the use of a brief isometric contraction of the muscle prior to a static stretch (Bandy &
Irion, 1994). Finally, dynamic stretching method involves an active warming and
integration of movement patterns and skills integral to the athlete’s sport (Bandy & Irion,
1994)

Static and dynamic stretching are two methods that can be affectively executed by
an athlete with no assistance. PNF and ballistic stretching on the other hand should be
performed only by a trained individual so that it is not only effective, but does not harm
the athlete. Because the overall anatomy and physiology of the shoulder complex does
not suggest if static or dynamic stretching is a more effective stretching protocol it is
important to investigate which stretching method will produce the greatest range of
motion and peak torque.

1.2 SIGNIFICANCE OF THE PROBLEM

The majority of the literature conducted on static and dynamic stretching

examines hamstring flexibility and the effects of lower body stretching on performance

such as long jump and vertical jump. Researchers have also investigated how long these

effects last. However, there is a lack of research on upper extremity stretching and its
effect on range of motion and performance. This information is essential to upper
extremity athletes such as softball, baseball, and volleyball players who place just as
much (or more) strain on their shoulder as their lower extremity.

To date, there has been only one study that has investigated the effects of static
stretching on shoulder range of motion. Laudner, Sipes, and Wilson (2008) examined the
effect of sleeper stretches (static stretches) on posterior shoulder/ capsule tightness, and
range of motion in the shoulder complex. The researchers concluded that sleeper
stretches (see page 40) increased posterior shoulder motion and internal shoulder rotation.
However, external shoulder rotation was not significantly different after athletes
performed sleeper stretches (Laudner, et al., 2008). In addition, this study did not
examine the effects of dynamic stretching on shoulder range of motion.

There are several other studies that have examined the impact of static stretching
on overall flexibility. A study by Bandy and Irion (2007) examined the effect of time and
flexibility on static stretching on hamstring muscle flexibility. This study concluded that
30 s was the optimal time to enhance the flexibility of the hamstring muscles (Bandy &
Irion, 2007). In 2004, Nelson and Bandy tried to determine if they could improve
hamstring flexibility of high-school aged males with either a six week eccentric exercise
program or a static stretching protocol. This study concluded that the gains in range of
motion with the eccentric training were equal to those made by statically stretching the
hamstring muscles (Nelson & Bandy, 2004). Finally, DePino, Webright and Arnold
(2000) investigated the duration of maintained hamstring flexibility. These authors

concluded that the effects of stretching only lasted 3 min. after the cessation of stretching.

In addition to these studies concentrating solely on the hamstring muscles, none of these
authors examined dynamic stretching and its’ effect on hamstring range of motion and
peak torque.

Dynamic stretching has recently become popular as a stretching protocol for pre-
practice activities to improve range of motion. Dynamic stretching is effective due to its
ability to elevate core body temperature, enhance excitability of motor units, and develop
kinesthetic awareness (Fredrick & Szymanski, 2001). Dynamic stretching has been
shown to be just as effective as static stretching in improving flexibility (Winters, et al.,
2004). Duncan and Woodfield (2006) showed no significant differences in overall
flexibility when comparing dynamic and static stretching protocols. Winters et al. (2004)
concluded that passive and active stretching are equally effective for increasing range of
motion when investigating their effect in the hip flexors. These studies indicate that there
is no significant difference between static and dynamic stretching in improving overall
flexibility. Both are effective in increasing range of motion. The only difference at this
time is that the length of the effects of dynamic stretching are unknown.

Research has shown that static stretching has both positive and negative effects on
performance. Performance has been defined as peak torque (Ryan et al., 2008), speed
during a timed run (Taylor, Sheppard, Lee, & Plummer, 2008), and the explosive force
during a vertical or standing long jump (Rubini, Costa, & Gomes, 2007). A review of
literature by Rubini, et a1. (2007) revealed an overall negative effect of static stretching
on strength performance. They found decreases in performance ranging anywhere from
4.5% to 28% after static stretching was performed. In another study, researchers looked at

the immediate effects of 2, 4, and 8 min. of passive stretching on peak torque and range

of motion of the plantarflexors. This study concluded no decrease in torque and
temporary improvements in range of motion (Ryan et al., 2008). A study in 2009
revealed a consistent tendency for sprint ability times to be slower after the static
stretching interventions. The sprint times were also slower in the change of direction
speed tests after static stretching when compared to the control (Beckett, Schneiker,
Wallman, Dawson, & Guelfi, 2009). Chronic static stretching, when compared to acute
static stretching, was actually shown to improve specific exercise performances. Over the
course of 10 weeks those participants who stretched on a consistent basis compared to the
control group improved in their standing long jump, vertical jump, and 20 meter sprint
(Kokkonen et al., 2007).

Taylor et a1. (2008) investigated whether adding a sport specific warm-up
component after static stretching would be helpful. They directly compared dynamic
stretching and static stretching in this study. When directly compared, static stretching
resulted in significantly worse performances compared to dynamic stretching. However,
there were no significant differences between static stretching paired with a sport specific
warm-up and dynamic stretching (Taylor et al., 2008). There are several other studies that
investigate the effects of static stretching on performance. Overall, static stretching seems
to be more detrimental than helpful; itt decreases explosive power, force, and jump height
(Shrier, 2004). Static stretching seems to help only when paired with a sport specific
warm-up or done chronically to improve overall flexibility.

Dynamic stretching has been shown to have a positive impact on performance for
high power or explosive actions such as jumping (Saez de Villarreal, Gonzalez-Badillo &

Izquierdo, 2007). It uses speed of movement, momentum, and active muscular effort to

effectively stretch the muscle tissue (Fredrick & Syzmanski, 2001 ). One study tested
different warm-up protocols and their effects on performance. The results of this study
suggest that high intensity dynamic loading as well as sport specific warm-ups can lead to
greater acute positive effects on performance (Saez de Villarreal et al., 2007). Herman
and Smith (2008) discovered that a 4 week dynamic stretching protocol can produce
better results in power, strength, muscular endurance, anaerobic capacity, and agility
performance than a static stretching protocol.

Overall, most of the research indicates that dynamic stretching has a more
positive effect on performance than static stretching. Several studies concluded that
dynamic stretching protocols result in better results in long jump performance, vertical
height performance, and peak quad torque. However, there is no research indicating how
long the effects of a dynamic stretch last. Furthermore, there is no current research on
dynamic stretching for the upper extremity. Therefore, this study is essential to determine
whether a static or dynamic stretching protocol should be followed for optimal
performance in upper extremity athletes. If one protocol provides significant
improvements in range of motion and peak torque over the other, then coaches and
clinicians may change their stretching routines for their athletes to the stretching protocol
that is most effective.

1.3 PURPOSE OF THE STUDY

The purpose of the study was to investigate whether a static or dynamic stretching

protocol is more effective at the shoulder complex as measured by range of motion and

peak torque.

1.4 HY POTHESES:
1. Dynamic stretching will produce greater range of motion at the shoulder complex
than static stretching.
2. Dynamic stretching will produce greater peak torque at the shoulder complex than
static stretching.
1.5 OPERATIONAL DEFINITIONS OF TERMS

fillistic stretching; A bouncing movement where repetitive contractions of an
agonist muscle (prime mover) work to stretch an antagonist muscle (a muscle that
contracts with and limits the action of an agonist with which it is paired) (Bandy & Irion,
1994)

Mg - The joint capsule surrounds the joint as a whole and is attached
medially to the margin of the glenoid fossa beyond the labrum. The capsule is thin and
does not contribute very much to the stability of the joint by itself. It relies on the
reinforcement by ligaments and the attachment of the rotator cuff muscles (Peat, 1986).
The capsule is lined by a synovial membrane attached to the glenoid rim and anatomical
neck inside the capsular attachments (Terry & Chopp, 2000).

Dynamic stabilizers - The dynamic stabilizers include the four muscles of the
rotator cuff, as well as the deltoid and scapular stabilizers. The rotator cuff is made up of
the supraspinatus, infi'aspinatus, teres minor, and subscapularis (Terry & Chopps, 2000).

Dynamic stretching routine - This method involves an active warming and
integration of movement patterns and skills integral to the athlete’s sport (Cone, 2007).

Law - The glenoid labrum is a rim of fibrocartilaginous tissue attached around

the margin of the glenoid fossa (Peat, 1986). Due to its location at the glenoid margin, the

labrum extends the articular surfaces, thereby increasing the contact surface area and
adding to the stability of the shoulder (Terry & Chopp, 2000). The inner surface of the
labrum is covered with synovium, while the outer surface attaches to the capsule and is
continuous with the periosteum of the scapular neck (Terry & Chopp, 2000). The
labrum’s shape adapts for the rotation of the humeral head, adding flexibility to the edges
of the glenoid fossa.

Propfiiocafiive neuromuscular fgciligrtion (PNID — Involves a technique of
contract-relax or hold-relax using a brief isometric contraction of the muscle prior to a
static stretch (Bandy & Irion, 1994).

Range of motion -— Range of motion can be defined as the available movement
within a specific joint. In this study, the range of motion tests will identify the athletes’
ability to move their shoulder into flexion, extension, internal rotation and external
rotation.

Rotgtor cuff @0188 — The rotator cuff is made up of four muscles: a)
supraspinatus, b) infiaspinatus, c) teres minor, and d) subscapularis (Terry & Chopps,
2000). These muscles act as the dynamic steering mechanism for the humeral head. Due
to the rotator cuff muscles being closer to the center of rotation on which they act, they
are able to provide stability to a dynamic fulcrum during glenohumeral abduction (Terry
& Chopp, 2000).

Shoulder girdle - The shoulder girdle is composed of the scapula, clavicle, and
sternum (Terry & Chopp, 2000).
Shoulder ioint - The shoulder joint is the connection of the girdle with the

humerus (Terry & Chopp, 2000).

Static stabilizers - The static stabilizers include the labrum, capsule, and ligaments
(Peat, 1986).
Static stretching — The muscle is slowly elongated to tolerance (comfortably with

no pain) and the position is held for an extended period of time (Prentice, 2003).

10

CHAPTER 2
REVIEW OF LITERATURE

2.1 INTRODUCTION

The review of literature is divided into five major sections. First, an overview of
shoulder anatomy including bony anatomy, bony and muscular articulations, static
stabilizers and dynamic stabilizers is discussed. Second, an overview is provided of
muscle physiology including what happens to the muscle tissue during stretching. Third,
the four specific types of stretching that are utilized in athletes are described. The fourth
section examines the effects of static stretching on range of motion and performance at
the shoulder joint. Finally, this review of literature discusses dynamic stretching and its
effect on range of motion and performance at the shoulder joint.
2.2 SHOULDER ANATOMY

The structure of the shoulder complex allows the upper extremity to have a large
range of motion (Peat, 1986). However, this unrestricted radius of action leaves the
anatomical structures of the shoulder very vulnerable (Terry & Chopp, 2000). There are
two components of the shoulder complex: a) the shoulder girdle and b) the shoulder joint.
The shoulder girdle is composed of the scapula, clavicle, and sternum. The shoulder joint
is the connection of the girdle with the humerus. Due to this anatomical structure, there is
more mobility, which results in less stability in the shoulder. The shoulder complex can
be broken down into four categories: the bony anatomy, the bony and muscular

articulations, the static stabilizers, and the muscles or dynamic stabilizers.

ll

2.2.1 BONY ANATOMY

The humerus is the largest and longest bone of the shoulder joint, with its
proximal portion consisting of the half spheroid articulating surface or head, greater
tuberosity, bicipital groove, lesser tuberosity and proximal humeral shaft (Terry &
Chopp, 2000). The four rotator cuff muscles are the subscapularis, supraspinatus,
infraspinatus, and teres minor. The greater tuberosity is the insertion point of the
supraspinatus, infraspinatus, and teres minor, while the lesser tuberosity is the insertion
point for the subscapularis. The bicipital groove is the insertion point for the long head of
the biceps brachii (Terry & Chopp, 2000).

The scapula is a large, thin, triangular bone lying on the posterolateral aspect of
the thorax, overlying ribs two through seven, that serves mainly as a site of muscle
attachment (Terry & Chopp, 2000). The spine of the scapula separates the supraspinatus
muscle fiom the infraspinatus muscle, and, extends superiorly and laterally to form the
base of the acromion. The spine functions as part of the insertion of the trapezius muscle,
as well as the origin of the posterior deltoid muscle. The acromion serves as a lever arm
for function of the deltoid and articulates with the distal end of the clavicle forming the
acromioclavicular joint (Terry & Chopp, 2000). The acromion forms the space for the
rotator cuff, and variations in acromial shape can affect contact and wear on the rotator
cuff. The coracoid process projects anteriorly and laterally fi'om the upper border of the
head of the scapula (Prescher, 2000). The superior surface serves as the origin of the two
coracoclavicular ligaments (trapezoid and conoid). The coracoid tip serves as the origin
of the coracobrachialis muscle and the short head of the biceps brachii, as well as the

insertion of the pectoralis minor muscle. In addition, the coracohumeral and

12

coracoacromial ligaments originate on the coracoid. The scapular notch lies just medial to
the base of the coracoid and is spanned by the transverse scapular ligament. The glenoid
fossa, or cavity, represents the bony articulating surface for the humerus. Its articular
surface is only one third to one fourth that of the humeral head hence providing only a
small contribution to glenohumeral stability (Terry & Chopp, 2000).

The clavicle is the sole connector of the trunk to the shoulder girdle via the
stemoclavicular joint medially and the acromioclavicular joint laterally (Terry & Chopp,
2000). The clavicle has a double curve along its long axis. The flat outer third serves as
an attachment point for muscles and ligaments, whereas the tubular medial third accepts
axial loading. The middle third transitional zone is the thinnest portion and weak
mechanically (Terry & Chopp, 2000). The clavicle serves as a site for muscle
attachments, a barrier to protect underlying neurovascular structures, and stabilizes the
shoulder complex by preventing it fi'om displacing medially with activation of the
pectoralis and other axiohumeral muscles (Peat, 1986). The clavicle also prevents inferior
migration of the shoulder girdle through the strong coraclavicular ligament (Peat, 1986).
Finally, the sternum is the connector of the clavicle to the rest of the body.

2.2.2 BONY AND MUSCULAR ARTICULATIONS

The bony and muscular articulations include the glenohumeral joint, the
acromioclavicular joint, stemoclavicular joint and the scapulothoracic articulation. The
glenohumeral joint is considered a multiaxial ball and socket synovial joint (Peat, 1986).
It also considered to be well suited for extreme mobility with its mismatched large
humeral head and small glenoid articular surface (Terry & Chopp, 2000). The articular

surfaces include the head of the humerus and the glenoid fossa of the scapula (Peat,

l3

1986). The bony architecture of the glenohumeral joint, with its large articulating
humeral head and relatively small glenoid surface, relies heavily on the ligament and
muscular stabilizers throughout its motion are (Terry & Chopp, 2000). If any of the static
or dynamic stabilizers are injured by trauma or overuse, the shoulder is at an increased
risk for injury.

The acromioclavicular joint is a diarthrodial joint between the lateral border of the
clavicle and the medial edge of the acromion. The stability of this joint is provided by the
static stabilizers (Terry & Chopp, 2000). The curvature of this joint allows the acromion
and the scapula to glide forward or backward over the lateral end of the clavicle. This
movement of the scapula keeps the glenoid fossa continually facing the humeral head.
This joint is important because of its role in the movement of the arm. The
acromioclavicular joint allows three degrees of freedom; these movements take place
between the acromion and lateral end of the clavicle. They include movement about a
vertical axis, around a frontal axis, and about a sagittal axis. The two major movements
are a gliding movement as the shoulder joint flexes and extends, and, elevation and
depression of the scapula and humerus during abduction (Peat, 1986).

The stemoclavicular joint is the only true articulation between the upper extremity
and the axial skeleton (Terry & Chopp, 2000). The medial end of the clavicle is bound to
the sternum, the first rib, and its oostal cartilage. The movements of the stemoclavicular
joint allow elevation and depression of the clavicle, as well as protraction and retraction
(Peat, 1986).

The scapulothoracic articulation is not a true joint, but rather a space between the

posterior thoracic cage and the concave surface of the anterior scapula. The

14

scapulothoracic articulation allows increased shoulder movement beyond the 120 degrees
offered solely by the glenohumeral joint. There are 17 muscles attach to or originate from
the scapula; their main function is to stabilize the scapula and provide movement (Terry
& Chopp, 2000).

2.2.3 STATIC STABILIZERS

The static stabilizers include the labrum, capsule, and ligaments. The glenoid
labrum is a rim of fibrocartilaginous tissue attached around the margin of the glenoid
fossa (Peat, 1986). Due to its location at the glenoid margin, the labrum extends the
articular surfaces, thereby increasing the contact surface area and adding to the stability
of the shoulder (Terry & Chopp, 2000). The inner surface of the labrum is covered with
synovium, while the outer surface attaches to the capsule and is continuous with the
periosteum of the scapular neck (Terry & Chopp, 2000). The labrurn’s shape adapts for
the rotation of the humeral head, adding flexibility to the edges of the glenoid fossa.

The joint capsule surrounds the joint as a whole and is attached medially to the
margin of the glenoid fossa beyond the labrum. The capsule is thin and does not
contribute very much to the stability of the joint by itself. It relies on the reinforcement
by ligaments and the attachment of the rotator cuff muscles (Peat, 1986). The capsule is
lined by a synovial membrane attached to the glenoid rim and anatomical neck inside the
capsular attachments (Terry & Chopp, 2000).

The ligaments of the shoulder are the soft tissue structures that connect bone to
bone. Within the shoulder complex there are several ligaments, that include the
coracohumeral ligament, the glenohumeral ligaments (superior, middle, inferior), the

stemoclavicular ligament, coracoclavicular ligament and the acromioclavicular ligament.

15

The coracohumeral ligament is a thick band of capsular tissue originating from the base
of the lateral coracoid and inserting into the lesser and greater tuberosities (Peat, 1986). It
is one of the most important ligarnentous structures in the shoulder complex (Peat, 1986).
The superior glenohumeral ligament extends from the anterosuperior edge of the glenoid
to the top of the lesser tuberosity (Terry & Chopp, 2000). The superior glenohumeral
ligament assists in preventing downward displacement of the humeral head (Peat, 1986).
The middle glenohumeral ligament originates fi'om the supraglenoid tubercle, superior
labrurn, or scapular neck and inserts on the medial aspect of the lesser tuberosity (Peat,
1986). This ligament limits lateral rotation up to 90 degrees of abduction and is an
important anterior stabilizer (Terry & Chopp, 2000). The inferior glenohumeral ligament
is the thickest of the glenohumeral structures. This ligament attaches to the anterior,
inferior, and posterior margins of the glenoid labrum and passes laterally to the inferior
aspects of the anatomical neck of the humerus (Peat, 1986). Its main function is to
support the joint in the upper ranges of abduction and prevent anterior subluxation and
dislocation (Terry & Chopp, 2000).” The stemoclavicular ligament connects the sternum
and the clavicle. The coracoclavicular ligament connects the coracoid and the clavicle,
while the acromioclavicular ligament connects the acromion and the clavicle.

2.2.4 DYNAMIC STABILIZERS

The dynamic stabilizers include the four muscles of the rotator cuff, as well as the
deltoid and scapular stabilizers. The rotator cuff is made up of the supraspinatus,
infi’aspinatus, teres minor, and subscapularis. These muscles act as the dynamic steering
mechanism for the humeral head. Due to the rotator cuff muscles being closer to the

center of rotation on which they act, they are able to provide stability to a dynamic

16

fulcrum during glenohumeral abduction (Terry & Chopp, 2000). On the other hand, any
injury to the rotator cuff can result in considerably less force of elevation in the shoulder
joint (Peat, 1986). To palpate the rotator cuff muscles the patients arm must be hanging at
their side. The supraspinatus muscle lies just under the acromion. The infi'aspinatus
muscle can be palpated below the spine of the scapula and posterior deltoid muscle.
Inferior to the infraspinatus, the teres minor muscle can be palpated along the lateral
scapula border. The subscapularis is the one rotator cuff muscle that cannot be palpated
as it located on the subscapularis fossa

The deltoid muscles are made up of three areas: the anterior deltoid originates
from the lateral clavicle, the middle deltoid starts at the acromion and a posterior deltoid
originates from the spinous process of the scapula. All three areas of the deltoid muscle
insert on the deltoid tuberosity of the humerus. The anterior and middle deltoids are
responsible for elevation in the scapular plane and assist in forward elevation with help
fi'om the pectoralis major and biceps brachii (Terry & Chopp, 2000).

The scapulothoracic muscles include: trapezius, rhomboids major and minor,
levator scapulae, serratus anterior and pectoralis minor. The trapezius is a large muscle
that begins or originates from the base of the skull to the upper lumbar vertebrae and
inserts on the lateral aspect of the clavicle, acromion, and scapular spine. Its main
fimction is to act as a scapular retractor and elevator of the lateral angle of the scapula. It
can be palpated from the neck region down to T12. The rhomboid muscles (major and
minor) originate frOm the spinous processes of C7 and T1 and T2 to T5. They insert on
the medial aspect of the scapula and retract and elevate the scapula. To palpate, the

patient must place arm behind back while resisting rotation. The rhomboids can be found

17

between the scapula and spinous processes. The levator scapulae originates on the
transverse processes of the cervical spine and inserts on the superior angle of the scapula.
The levator scapulae elevates the superior angle, which results in upward and medial
rotation of the scapular body. The serratus anterior is located on the front and lateral side
of the chest below ribs five and six. It originates from the bodies of the first nine ribs and
anterolateral aspect of the thorax. The serratus anterior inserts fiom the superior to
inferior angle of the scapula. Activating this muscle group causes scapular protraction
and upward rotation. The pectoralis minor muscle begins at the anterior portion of the
second through fifth ribs and inserts on the base of the coracoid. This muscle protracts
and rotates the scapula inferiorly (Terry & Chopp, 2000).

2.2.5 RANGE OF MOTION

As previously mentioned, the shoulder complex is a highly moveable joint. Its
range of motion is made possible through all four joints working together as one
complex. An Apley’s Scratch test is a simple way to measure the available range of
motion within the shoulder. This test examines limited range of motion or asymmetry of
movements when comparing the affected and unaffected shoulders. The patient is seated
or standing and he/ she is instructed to simply touch the opposite side shoulder with
his/her hand. Any difference in the inability to touch the opposite shoulder shall be
considered a positive finding. The normal motion for the shoulder joint is 180 degrees of
abduction, 180 degrees of flexion, 55 degrees of internal rotation, 45 degrees of
adduction, 45 degees of extension and 80-100 degrees of external rotation (Terry &
Chopp, 2000). The shoulder girdle also includes the following movements: protraction,

retraction, upward rotation, downward rotation, elevation, and depression.

18

The shoulder joint and girdle move together in what is known as “scapulohumeral
rhythm.” This is the combined movement of the scapula and humerus during elevation.
As the arm moves beyond 30 degrees of abduction or 60 degrees of flexion the scapula
rotates one degree fiom every two degrees of humeral movement. And for every three
degrees of abduction, two degrees of movement occurs in the glenohumeral joint as one
degree occurs at the scapulothoracic joint. The purpose of this combined movement is to
increase range of motion while still maintaining stability.

Range of motion within the shoulder is also reliant on bursae; these are small
fluid-filled sacs made of white fibrous tissue and lined with synovial membrane (Powers
& Howley, 2004). Bursae provide a cushion between bones and tendons and/or muscles
around a joint. There are two that are particularly important for total movement within
the shoulder complex. These are the subacromial and subscapular bursae. These bursae
sacs provide for smoother motion within the shoulder.

2.3 PHYSIOLOGY OF STRETCHING

In order to make gains during a stretching session it is important to know how
each of the structures within the muscle interact with one another. Skeletal muscle
contains many types of sensory receptors: chemoreceptors, muscle spindles, and golgi
tendon organs. A chemoreceptor is a specialized free nerve ending that sends information
to the central nervous system (Powers & Howley, 2004). It does this in response to
changes in muscle pH, concentrations of extracellular potassium, and changes in Oz and
C02 tension (Powers & Howley, 2004). In order for the nervous system to be successful
it must receive continuous sensory feedback from the contracting muscle. This sensory

feedback includes information concerning the tension developed by a muscle and

19

accounts for the muscle length. Golgi tendon organs provide the central nervous system
with feedback concerning the tension, while the muscle spindles provide sensory
information concerning the relative muscle length (Powers & Howley, 2004).

Muscle spindles are essential to the stretching process, but they also assist in the
regulation of movement and help to maintain posture (Powers & Howley, 2004). They
are composed of several thin muscle cells (intrafusal fibers) that are surrounded by a
connective tissue sheath. Muscle spindles insert into connective tissue within the muscle
and run parallel with muscle fibers (Powers & Howley, 2004). There are two types of
sensory nerve endings within a muscle spindle. The primary endings respond to dynamic
changes in muscle length and the secondary endings provide the central nervous system
with continuous information concerning static muscle length. In addition to sensory
neurons, muscle spindles are innervated by gamma motor neurons, which stimulate the
intrafirsal fibers to contract with the connective tissue sheath (Saladin, 2004). Gamma
motor neuron stimulation causes the central region of the intrafusal fibers to shorten,
which causes the spindle to tighten. This is more commonly known as the stretch reflex
(Powers & Howley, 2004).

During stretching specifically, muscle spindles are responsible for detecting the
stretch of the muscle, sending sensory neurons to conduct action potentials to the spinal
cord and to synapse with alpha motor neurons (Powers & Howley, 2004). This then
causes the stimulation of the alpha motor neurons and the muscle contracts and resists
being stretched (Powers & Howley, 2004).

The golgi tendon organs are located within the tendon and are in series with the

connective tissue sheath or extrafusal fibers. These organs detect tension applied to a

20

tendon and send sensory neurons to conduct action potentials to the spinal cord and to
synapse with inhibitory intemeurons that synapse with alpha motor neurons (Powers &
Howley, 2004). Inhibition of the alpha motor neurons causes muscle relaxation, relieving
the tension applied to the tendon. This is more commonly referred to as the golgi tendon
reflex (Saladin, 2004). Golgi tendon organs are considered safety devices that help
prevent excessive force during muscle contraction (Powers & Howley, 2004). Therefore,
golgi tendons moderate muscle contractions before it tears a tendon or pulls it loose from
the muscle or bone (Saladin, 2004).
2.4 FOUR TYPES OF STRETCHES

Good flexibility is essential for successful physical performance; it has long been
thought to decrease the incidence of musculotendinous injuries, minimize and alleviate
muscle soreness and improve athletic performance (Prentice, 2003). A decreased range of
motion can lead to decreased performance capabilities as well as uncoordinated and
awkward movements (Prentice, 2003). Athletes who participate in overhead activities
such as baseball, softball, and volleyball typically present with posterior shoulder
tightness, therefore it is essential to discover an effective way to increase their range of
motion in order for these athletes to practice proper kinematics and kinetics (Laudner,
Sipes, &Wilson, 2008). Recent research has shown that lesions are commonly associated
with posterior shoulder tightness resulting in subacromial impingement (Tyler, Nicholas,
Roy, & Gleirn, 2000), superior labrum anterior to posterior (SLAP) lesions (Grossman, et
al., 2005) and internal impingement (Myers, Laudner, Pasquale, Bradley & Lephart,

2006)

21

There are four ways to stretch, three of which are very common and well known,
while the fourth, dynamic stretching, is becoming more popular in the current athletic
population (Bandy & Irion, 1994). The first method is ballistic stretching, which involves
a bouncing movement where repetitive contractions of an agonist muscle (prime mover)
work to stretch an antagonist muscle (a muscle that contracts with and limits the action of
an agonist with which it is paired) (Bandy & Irion, 1994). The muscle spindles tend to
tighten during this method instead of relaxing and can lead to possible muscle soreness or
injury (Prentice, 2003). This stretching method is not commonly used in athletic
populations today as it has been discarded for more effective stretching methods. An
example of this type of stretch is a bouncing hamstring stretch. This involves reaching for
ones toes in a bouncing, repetitive manner.

The second method is static stretching which involves the muscle slowly
elongated to tolerance (comfortably with no pain) and the position is held for an extended
period of time (Prentice, 2003). Research has shown that the optimal way to increase
flexibility over time is to hold a static stretch for 30 to 45 seconds (Bandy & Irion, 1994).
This extended amount of time allows the golgi tendon organs to override impulses fi'om
the muscle spindle following its initial reflex resistance (Prentice, 2003). Laudner et al.
(2008) concluded that sleeper stretches (static stretches) for the shoulder are effective in
increasing shoulder range of motion in the dominant arm of baseball players. Another
study suggests that 40 min. of static stretching three times per week for 10 weeks
increases flexibility, strength, endurance, and power in the lower extremity (Kokkonen, et
al., 2007). When Nelson and Bandy (2004) compared eccentric training (lengthening of

the muscle) and static stretching, they discovered that the gains achieved in range of

22

motion in the hamstring muscles during eccentric training were equal to those made by
statically stretching the hamstring muscles. The major advantage with static stretching is
its convenience because it can be done without the assistance of a partner. An example of
a static stretch is a seated hamstring stretch. This is where on reaches for their toes and
holds the stretch for an extended time period.

The third common method of stretching is the propioceptive neuromuscular
facilitation (PNF) technique of contract-relax or hold-relax; these involve the use of a
brief isometric contraction of the muscle prior to a static stretch (Bandy & Irion, 1994).
According to clinicians, PNF is the best technique to improve overall flexibility. Both
isometric and concentric (shortening) muscle actions completed immediately before the
passive stretch (stretch applied by clinician) help to achieve autogenic inhibition
(Prentice, 2003). Autogenic inhibition is a reflex relaxation that occurs in the same
muscle where the golgi tendon organ is stimulated (Prentice, 2003). Often the isometric
contraction is referred to as 'hold' and the concentric muscle contraction is referred to as
'contract' (Bandy & Irion, 1994). A disadvantage to PNF stretching is that an experienced
clinician (physical therapist or athletic trainer) is required to administer an effective PNF
stretch.

An example of a PNF stretch is a hamstring slow-reversal-hold-relax technique.
This is done with the athlete lying supine with the knee extended and the ankle flexed to
90 degrees, the athletic trainer passively flexes the hip joint to the point at which there is
a slight discomfort in the muscle. At this point the athlete begins pushing against the
athletic trainer’s resistance by contracting the hamstring muscle. After pushing for ten

seconds, the hamstring muscles are relaxed and the agonist quadriceps muscle in

23

contracted while the athletic trainer applies passive pressure to further stretch the
antagonist harnstrings. This action should move the leg so that there is increased hip joint
flexion.

The fourth and final stretching method is a dynamic stretching routine. This
method involves an active warming and integration of movement patterns and skills
integral to the athletes’ sports. According to research, the musculoskeletal benefits of
active warming is an increase in temperature in exercising muscle, resulting in a general
decrease in muscular viscosity, and an increase in muscle pliability (Cone, 2007).
According to Cone (2007), movements occur in all planes and ranges of motion, and at
both slow and maximal speed. Therefore it is logical for flexibility to progress in three
areas: control, speed, and complexity (Cone, 2007). Dynamic stretching begins with
simple stretches at a slow speed with controlled movements. As the stretching progresses
the movements become faster, more complex, and less controlled. Faigenbaum,
McFarland, Ratamess, Kang and Hoffinan, (2006) concluded that a dynamic warm-up
with a weighted vest may be the most effective warm-up protocol for enhancing jumping
performance. An example of a dynamic stretch is overhead arm circles. This mimics the
motion of an overhead throw while actively moving the muscle in multiple planes.

In conclusion, both static and dynamic stretching are two methods that can be
affectively executed by an athlete with no assistance. PNF and ballistic stretching on the
other hand should be performed only by a trained individual so that it is not only
affective, but does not harm the athlete.

2.5 STATIC STRETCHING

2.5.1 EFFECT OF STATIC STRETCHING ON RANGE OF MOTION

24

Most of the current research on static stretching has addressed increasing range of
motion or flexibility in the hamstring (Bandy & Irion, 2007). However, only one study
has specifically addressed increasing range of motion in the shoulder complex using a
form of static stretching. Laudner, Sipes, and Wilson (2008) examined the effect of
sleeper stretches on posterior shoulder/capsule tightness, and range of motion in the
shoulder complex.

During this study, 33 NCAA Division I baseball players’ glenohumeral horizontal
adduction motion and internal and external shoulder rotation were measured prior to the
stretches. A sleeper stretch is applied in the side lying position, with scapular motion
restricted. The shoulder is then internally rotated to isolate the posterior soft tissue
restraints. After the sleeper stretch was applied for three 30 5 intervals, the measurements
were taken again (Laudner, Sipes, &Wilson, 2008). This study had one clinician apply
the stretch for each athlete. Although this controlled for internal validity within the study
it may not have much external validity. In an athletic setting, it may be more practical to
have the athletes apply the stretch on each other' due to limited time available before
practice for individual stretching by an ATC. The results of this study demonstrated
increased posterior shoulder motion and internal shoulder rotation, however, external
shoulder rotation was not significantly different after the stretches (Laudner, Sipes,
&Wilson, 2008). Further research is needed to determine what other shoulder stretches
can successfully result in increased range of motion, the optimal time to hold the stretch
and how long the affects of stretching last.

A study conducted by Bandy and Irion (2007) examined the effect of time and

flexibility on static stretching on the flexibility of the hamstring muscles. Flexibility was

25

defined as “the range of motion available in a joint or a group of joints that is influenced
by muscles, tendons, ligaments, and bones” (Bandy & Irion, 2007). During this study,
flexibility of the hamstring muscles was determined by measuring knee extension range
of motion with the femur maintained in 90 degrees of hip flexion using a goniometer.
Measurements were taken before and after 6 weeks of static stretching. The results of this
study suggested that 30 s is an effective time of stretching for enhancing the flexibility of
the hamstring muscles (Bandy & Irion, 2007).

Nelson and Bandy (2004.) conducted a research study to determine if the
hamstring flexibility of high-school aged males would improve with a 6 week eccentric
exercise program over a static stretching protocol. The results of this study showed no
difference between the eccentric and static-stretching groups. Therefore, the gains in
range of motion with eccentric training were equal to those made by statically stretching
the hamstring muscles (Nelson & Bandy, 2004).

In another study conducted by DePino et a1. (2000) the duration of maintained
hamstring flexibility was examined. This study had 30 male subjects with limited
hamstring flexibility perform four 30 s static stretches separated by 15 s rests. Their range
of motion was measured before and after the stretching protocol by a goniometer. In
order to determine how long the gains in flexibility actually lasted, hamstring flexibility
was measured at l, 3, 6, 9, 15, and 30 min. post static stretching. The researchers found
that the four consecutive 30 3 static stretches enhanced hamstring flexibility, however, the
effects only lasted 3 min. after cessation of the stretching protocol (DePino, Webright, &

Arnold, 2000). If this is the case, can stretching truly have an impact on performance?

26

2.5.2 EFFECT OF STATIC STRETCHING ON PERFORMANCE

Static stretching has been shown to have both positive and negative effects on
performance. Performance has been defined using numerous measures. Several studies
have defined performance as strength by measuring peak torque (Ryan et al., 2008);
others have defined it as speed during a timed run (Taylor et al., 2008). Performance has
also been defined as the explosive force during a vertical jump or standing long jump
(Rubini, Costa, & Gomes, 2007).

A review of literature by Rubini, Costa, and Gomes (2007) revealed a decrease in
strength performance ranging anywhere fiom 4.5% to 28% after static stretching with
most of the research being done on the lower body. Although most of the studies they
reviewed found acute decreases in strength following stretching, those decreases seemed
to be more prominent the longer the stretching protocol and the more exercises and sets
performed. The duration and number of these sets tended to exceed the ranges normally
recommended in the literature (Rubini et al., 2007 ). Their review of literature also
examined the effect of static stretching on vertical jump performance. The authors
concluded conflicting results with some studies demonstrating no decrease in vertical
jump after static stretching while others found decreases in performance (Rubini et al.,
2007)

Taylor et a1. (2008) conducted a research study to investigate if the negative effect
of static stretching could be restored when combined with a sport specific warm-up
component. Thirteen netball players completed two experimental warm-up conditions.
Day 1 warm-up involved a sub-maximal nm followed by 15 min of static stretching and a

netball specific skill warm-up. Day 2 followed the same procedures as Day 1 except the

27

static stretching was replaced with a 15 min dynamic warm-up. This allowed for a direct
comparison between static stretching and dynamic stretching. After the initial warm up
(static or dynamic) each participant performed a vertical jump and a 20 meter sprint.
Athletes then had their specific skill warm-up and re-perforrned a vertical jump and a 20
meter sprint. The static stretching condition resulted in significantly worse performance
than the dynamic warm-up in both vertical height and 20 meter sprint time. However,
there were no significant differences in either performance variable when the skill
specific warm-up followed the static or dynamic stretching warm-up routine (Taylor et
al., 2008).

In another study, researchers investigated the acute affect of 2, 4, and 8 min. of
passive stretching on peak torque and range of motion of the plantarflexors. The study
concluded that practical durations of stretching did not decrease peak torque compared
with the control, however, caused temporary improvements in range of motion (Ryan, et
al., 2008). Another study examined whether a static stretching routine decreased
isometric force, muscle activation, and jump power while improving range of motion of
the quadriceps (Power, Behm, Cahill, Carroll, & Young, 2004). Their results showed
significant decrements in the torque or force of the quadriceps. The force remained
significantly decreased for 120 min, although, there were no significant changes in jump
performance (Power et al., 2004).

A recent study examined the effects of static stretching on repeated sprint and
change of direction performance (Beckett, Schneiker, Wallman, Dawson, & Guelfi,
2009). On four separate occasions 12 male team sport players performed a standardized

warm-up followed by a test of either repeated sprint ability or change of direction speed.

28

Both tests involved three sets of six maximal sprint repetitions, with a 4 minute recovery
between sets. During the break, the athletes either completed a static stretching protocol
or rested. Results revealed a consistent tendency for repeated sprint ability times to be
slower after the static stretching interventions. Sprint times also tended to be slower in
the change of direction speed tests after static stretching when compared to the control.
These results suggest that an acute bout of static stretching of the lower limbs may
compromise repeated sprint ability performance as well as change of direction speed
performance (Beckett et al., 2009). Prior research has shown that muscular force and
power are lessened after acute bouts of static stretching (Power et al., 2004).

In contrast, chronic static stretching, compared to acute static stretching, may
improve specific exercise performance according to a study by Kokkonen and colleagues
(2007). These researchers conducted a study in which 38 participants were divided into a
stretching group and a control. The stretching group’s activity was limited to a 10 week,
40 rrrinutes a day, 3 days a week static stretching routine designed to stretch all the major
muscle groups in the lower extremity. The control group included the participants who
did not participate in physical activity on a regular basis for 10 weeks. Each participant
was measured before and after for flexibility, power (20 meter sprint, standing long jump,
vertical jump), strength (knee flexion and knee extension 1 repetition maximum), and
strength endurance (number of repetitions at 60% of 1 repetition maximum for both knee
flexion and knee extension). The static stretching group had significant improvements for
flexibility, standing long jump, vertical jump, 20 meter sprint, knee flexion 1 rep max,

knee extension 1 rep max, knee flexion endurance and knee extension endurance. These

29

results suggest that chronic static stretching exercises by themselves can improve specific
exercise performances (Kokkonen et al., 2007).

There are two theories why the chronic static stretching improved the
participant’s performance. One theory is that the chronic stretching caused strength gains.
The strength gains can be attributed to increases in muscle length. Increases in muscle
length lead to increases in contractile velocities and the forces generated at a given
shortening velocity. The other theory is that the improved performance may not be
related to the stretching exercises. It is possible that the strength gains in each leg were
the result of muscle contractions in the non-stretched leg when it was used to stabilize the
body during those stretches (Kokkonen et al., 2007).

Overall, static stretching seems to have more of a negative affect on performance
rather than a positive impact. In events that require explosive power, static stretching
tends to be a detriment. According to Shrier (2004) an acute bout of stretching does not
improve force or jump height. Static stretching as a whole is only successful when paired
with a sport specific warm-up or done chronically to improve overall flexibility.

2.6 DYNAMIC STRETCHING

2.6.1 EFFECT OF DYNAMIC STRETCHING ON RANGE OF MOTION

Dynamic stretching or an active warm-up has been shown to be an effective way
to stretch due to its ability to elevate core body temperature, enhance excitability of
motor units, and develop kinesthetic awareness (Fredrick & Szymanski, 2001). Active
warm-ups demonstrate an ability to increase range of motion just as effectively as static

stretching (Winters et al., 2004).

30

Researchers examined the acute effects of a dynamic warm-up protocol on
flexibility and vertical jump in children (Duncan & Woodfield, 2006). Forty children
participated in three experimental randomized conditions: no warm-up, static warm-up,
and dynamic warm-up. Low back and hamstring flexibility was assessed using the sit and
reach test while vertical jump height was assessed using a digital jump mat following
each condition. The results showed that there were no significant differences in a
dynamic warm-up protocol on overall flexibility. But in terms of vertical jump
performance, there was a significant increase in scores after a dynamic warm-up (Duncan
& Woodfield, 2006). These results indicate that an acute dynamic warm-up may enhance
performance in activities that require high power or explosiveness. The results may also
be an indication that an acute static warm-up may be detrimental to performance where
high power is required.

Another study looked at passive versus active stretching of hip flexor muscles in
subjects with limited hip extension (Winters et al., 2004). Thirty-three patients
participated in a randomized clinical trial each with decreased range of motion in their
hip flexors. Participants were divided into an active stretching group and a passive
stretching group. Hip extension range of motion was measured with the subjects at
baseline, 3 weeks, and 6 weeks after the start of the study. The results of this study
showed that there was an increase in range of motion with the active stretching group as
well as the passive stretching group. However, there were no significant differences
between the gains in range of motion. The researchers concluded that passive and active

stretching are equally effective for increasing range of motion (Winters et al., 2004).

31

Research done on dynamic stretching has indicated that it is equally effective as
static stretching in terms of increasing range of motion (Winters et al, 2004). However,
research has not investigated how long the effects of dynamic stretching last. Therefore,
additional research should be conducted to examine how long these effects last. A static
stretch has been shown to last for as long as six to eight minutes (Bandy & Irion, 1994).
However, if gains in range of motion last longer with dynamic stretching it may be the
more effective way to stretch before competition or practice.

2.6.2 EFFECT OF DYNAMIC STRETCHING ON PERFORMANCE

Dynamic stretching is defined as quickly moving a joint through its range of
motion with little resistance (Fredrick & Szymanski, 2001). It has been shown to have a
positive impact on performance for high power or explosive actions such as jumping
(Saez de Villarreal et al., 2007). Dynamic stretching uses speed of movement, momentum
and active muscular effort to effectively stretch. Physiologically, dynamic stretching
raises core body and deep muscle temperature, elongates active muscles (elasticity),
decreases the inhibition of antagonist muscles, and stimulates the nervous system
(arousal) (Fredrick & Szymanski, 2001). Many strength and conditioning coaches have
started to use this type of stretching for daily warm-ups.

Researchers examined the effect of different types of active or dynamic warm-ups
as a means to enhance height during vertical jump (Saez de Villarreal et al., 2007).
Twelve trained volleyball players performed different types of warm-ups on randomized
separate test occasions. Warm-up protocol one (WPl) consisted of three sets of five
jumps with extra load. Warm-up protocol two (WP2) consisted of two sets of four reps at

80% of one repetition maximum (RM) parallel squat and two sets of two reps at 85% of

32

one repetition max. The third warm-up protocol (W P3) was two sets of two reps at 90%
of one RM and two sets of one rep at 95% of one RM. The fourth warm-up protocol
(WP4) was three sets of five drop jumps. A fifth warm-up protocol (WP5) involved
specified warm-up for a volleyball match. A sixth warm-up protocol (WP6) was
performing three sets of five reps at 30% one RM. The final warm-up protocol (WP7)
was an experimental condition of no active warm-up (Saez de Villarreal ct al., 2007).

Each athlete in the experimental group gave a baseline vertical jump, 5 min. post
warm up vertical jump, and 6 hours post warm-up vertical jump. The results of this study
showed improvements in drop jump after WPl , WP2, WP3, and WPS and
countermovement jumps after WP2, WP5, WP3, and WP]. However, specific volleyball
warm-up protocol brought about the greatest effects on subsequent neuromuscular
explosive responses. The positive effects on jumping performance also lasted after long
recovery periods (6 hours) particularly when prior intensity dynamic actions were
performed (Saez de Villarreal et al., 2007). The results of this study suggest that high
intensity dynamic loading as well as sport specific warm-ups can lead to greater acute
positive effects on performance.

Another study examined the effects of active or dynamic warm-ups on
performance and force production. Hahn and colleagues (2007) measured force
production through torque, range of motion, and muscle activation. Data analysis showed
four main results: a) peak torque did not occur at the end of the stretch, but torque at the
end of the stretch exceeded the corresponding isometric torque, b) there was no
significant force enhancement following muscle stretch, but a small significant passive

force enhancement persisted for all stretch conditions, 0) forces during and following

33

stretch were independent of stretch amplitude, and d) muscle activation during and
following muscle stretch was significantly reduced (Hahn, Seiberl, & Schwirtz, 2007).
Although these results showed passive force enhancement, the study could not provide
direct evidence of force enhancement with active stretching.

Faigenbaum et a1. (2006) explored the acute effects of four warm-up protocols
with and without a weighted vest on anaerobic performance in 18 healthy high school
female athletes. After five minutes of jogging, athletes performed four randomly ordered
warm-up protocols. The first warm-up included five static stretches, each done two times
for 30 seconds (SS). The second warm-up was performing nine moderate to high
intensity dynamic exercises (DY). A third warm-up included the same nine dynamic
exercises performed with a weighted vest with two percent of body mass (DY4). The
fourth protocol included the same nine dynamic exercises but performed with a weighted
vest that represented six percent of their body mass (DY6). Athletes completing the
warm-up protocols followed by vertical jump, long jump, seated medicine ball toss and
10 yard sprint to determine positive or negative effects on performance. The results
showed that vertical jump performance was significantly greater after DY and DY2
compared with SS. Long jump performance was significantly greater after DY2
compared with SS. No significant differences between trials were observed for the seated
medicine ball toss or 10 yard sprint (Faigenbaum et al., 2006). These results indicate that
a dynamic warm-up performed with a vest weighted with two percent of body mass may
be the most effective warm-up protocol for enhancing jumping performance.

Another study done by Herman and Smith (2008) indicates that a four week

dynamic stretching warm-up intervention elicits long term performance benefits (Herman

34

& Smith, 2008). In this study 24 NCAA Division 1 wrestlers were randomly assigned to
complete either a four week dynamic warm-up (DWU) or a static warm—up (SWU). The
measures of performance included peak torque of the quadriceps and hamstrings,
medicine ball underhand throw, 300 yard shuttle, pull-ups, push-ups, sit-ups, broad jump,
600 meter run, sit and reach test, and trunk extension test. A four week dynamic
stretching protocol showed improvements in several performance areas, including
increases in quadriceps peak torque, broad jump, underhand medicine ball throw, sit-ups,
and push-ups. On the other hand, the static warm-up resulted in no observed
improvements (Herman & Smith, 2008). These findings suggest that a four week protocol
including dynamic stretching may help produce better power, strength, muscular
endurance, anaerobic capacity, and agility performance enhancements.

A similar study examined dynamic versus static stretching warm-up and their
effect on power and agility performance (McMillian, Moore, Hatler, & Taylor, 2006).
This study compared the two types of warm-ups using 30 cadets at the United States
Military Academy. On three consecutive days, subjects performed one of the two warm-
up routines (DWU or SWU) or performed no warm-up (NWU). Following the warm-up
the subject performed a t-shuttle run, underhand medicine ball throw for distance and 5-
step jump. Results showed better performance scores on all three tests after the dynamic
warm-up (McMillian et al., 2006). These results indicate that warm-up routines using
only static stretching may need to be reassessed.

Overall, a significant portion of the research indicates that dynamic stretching has
a more positive effect on performance than static stretching. Several studies indicate

significant improvements in long jump performance, vertical height performance, and

35

peak quad torque after performing a dynamic stretch or active warm-up for an assigned
period of time. However, only one study has examined the lasting effects of a dynamic
stretch. Therefore, more research is needed to validate the evidence. On the other hand,
one study concluded that there was no evidence of force enhancement with dynamic
stretching. Therefore it is vital that more research be conducted to truly determine the
best stretch for increasing range of motion and performance.
2.7 CONCLUSION

The purpose of this study was to determine an appropriate warm-up or stretching
protocol for athletes’ participating in an upper extremity sport. Most research on
stretching has focused primarily on lower body. A significant amount of the literature
primarily examined how to increase flexibility of the hamstring muscles and the effects
of lower body stretching on performance such as long jump and vertical jump.
Researchers also investigated how long these effects last. Upper extremity athletes such
as softball, baseball, and volleyball use their shoulder just as much or more than their
lower body. Therefore, research on the impact of stretching on the shoulder joint’s range
of motion and performance is extremely important. It would be beneficial for coaches and
clinicians working with upper extremity athletes to determine if a static or dynamic
stretching protocol could provide significant improvements in range of motion and/or

performance.

36

CHAPTER 3
METHODS

3.1 RESEARCH DESIGN

A randomized, counterbalanced, within—subj ect experimental design was used to
compare the two different types of stretching. The independent variable was stretching
technique (static, dynamic) and the dependent variables were range of motion and peak
torque.
3.2 SAMPLE POPULATION AND PARTICIPANT SELECTION

Thirty subjects from a mid-western university between the ages of 18 and 25
years were asked to volunteer for this study. All participants will be Division I NCAA
athletes participating in softball, baseball, or volleyball. Participants were excluded if
they had surgery on their dominant arm within the last 6 months. Participants were
excluded from the study if they had a previous injury to their dominant arm, elbow, wrist,
or hand 1 month prior to the study.
3.3 INSTRUMENTATION

3.3.1 GONIOMETRY

Goniometric measurements are used by physical therapists and athletic trainers to
quantify baseline limitations of range of motion, decide on appropriate therapeutic
interventions, and document the effectiveness of these interventions. In this study a large
plastic goniometer with a 10 in movable arm was used to measure shoulder flexion,
extension, internal rotation and external rotation. The scale of the goniometer is marked
in l-degree increments. A study done in 1987 confirmed the reliability of using a

goniometer in a clinical setting (Riddle, Rothstein, & Lamb, 1987).

37

3.3.2 BIODEX SYSTEM 3 DYNAMOMETER

The biodex system 3 dynarnometer was used to collect peak torque values for the
shoulder during this study. This system is reliable and valid and is specifically used for
isolated muscle testing and rehabilitation. A study in 2004 showed that the biodex system
3 dynarnometer was capable of producing valid measures of torque (Drouin, Valovich-
mcLeod, Shultz, Gansneder, & Penin, 2004). To assess validity measurement of each
variable using the Biodex system 3 dynarnometer was compared to a criterion measure of
position, torque, and velocity. Position was assessed at 5 degree increments across the
available range of motion of the dynarnometer. Torque measures were assessed
isometrically by hanging six different calibrated weights fiom the lever arm. Velocity
was assessed across a 70 degree are of motion by manually accelerating the weighted
lever arm. The biodex performed with acceptable mechanical reliability and validity on
all variables tested (Drouin et al., 2004).

Researchers have also shown that this dynarnometer is reliable in measuring
glenohumeral medial and lateral rotation (internal and external rotation) concentrically
and eccentrically in neutral to slightly abducted positions (Stickley, Hetzler, Freemyer &
Kimura, 2008). For this study, peak torque was assessed by the dynarnometer with the
shoulder in a neutral to slightly abducted position going from external to internal rotation.
Isokinetic internal and external rotation peak torque data was measured in
Newton*meters for the dominant arm.

3.4 STATIC STRETCHING INTERVENTION
Participants performed four different types of static stretches. Each of the four

stretches was performed 3 times for 30 8. Static stretch 1 was a shoulder stretch.

38

Participants stood tall, feet slightly wider than shoulder-width apart, knees relaxed and
slightly bent. They placed their dominant arm parallel with the ground across the front of
their chest. Participants bent their non-dominant arm up and used their non-dominant
forearm to ease the dominant arm closer to their chest. Participants felt the stretch in their
shoulder (See Figure 1).

Static stretch 2 was a shoulder and triceps stretch. Participants stood tall, feet
slightly wider than shoulder-width apart, knees relaxed and slightly bent. They placed
both hands above their head and then slid their dominant hand down the middle of their
spine. Their non-dominant hand pressed down on their dominant elbow to increase the
stretch. They felt the stretch in their shoulders and their triceps (see Figure 2).

Static stretch 3 was a biceps stretch. Participants stood tall, feet slightly wider
than shoulder-width apart, knees relaxed and slightly bent. They held their arms out to the
side, parallel with the ground. Facing forward, participants rotated their hands so their
palms faced to the rear. Then they stretched their arms back as far as possible while
clasping their hands together. Participants felt the stretch across their chest and in the
biceps (see Figure 3).

Static stretch 4 was a sleeper stretch. Participants positioned themselves laying
down on their dominant arm side with their dominant arm in fi'ont of them so it was
perpendicular to their body. They bent their right elbow to 90 degrees so that their
forearm was perpendicular to the floor and their fist is pointing up. Participants used their
non-dominant hand to gently push their dominant forearm and hand toward the ground
alongside their body until a stretch was felt in the back of their shoulder. If participants

started to feel a pinch, they eased up on the stretch (see Figure 4).

39

Figure 1: Shoulder stretch (static stretch l)

 

Figure 2: Shoulder and Triceps Stretch (static stretch 2)

 

Figure 4: Sleeper Stretch (Posterior Capsule) (static stretch 4)

 

40

3.5 DYNAMIC STRETCHING INTERVENTION

Participants performed four different types of dynamic stretches. Each of the four
stretches was performed 3 times for 30 3. Dynamic Stretch 1 was shoulder circles.
Participants stood tall, feet slightly wider than shoulder-width apart, knees slightly bent.
They raised their dominant shoulder towards their dominant ear, took it backwards, down
and then up again to the ear in a smooth action (see Figure 5).

Dynamic Stretch 2 was overhead/down and back arm swings. Participants stood
tall, feet slightly wider than shoulder-width apart, knees slightly bent. They kept their
back straight at all times. They swung both arms continuously to an overhead position
and then forward, down, and backwards (see Figure 6).

Dynamic Stretch 3 was side/front crossover arm swings. Participants stood tall,
feet slightly wider than shoulder-width apart, knees slightly bent. They again kept their
back straight at all times. Participants swung both arms out to their sides then cross them
in fiont of their chest (see Figure 7).

Dynamic Stretch 4 was a wall shoulder girdle stretch. Participants positioned their
back against the wall. They placed feet away from wall, slightly bending hips and knees.
They bent their elbows to 90 degrees and position back of arms against wall. Participants
then pushed shoulders and back of arms and hands into wall and slowly raised their arms
as high as possible maintaining contact with the wall. Still pushing shoulders arms, they

slowly lowered their arms to starting position (see Figure 8).

41

Figure 5: Shoulder Circles (dynamic stretch 1)

 

Figure 7: Side/Front Crossover Arm Swings (dynamic stretch 3)

 

42

Figure 8: Wall Shoulder Girdle Stretch (dynamic stretch 4)

 

3.6 PROCEDURES

Prior to data collection, this study was approved from the Institutional Review
Board (IRB) at Michigan State University. Each participant was asked to sign an
informed consent and complete a health history questionnaire (see Appendix A). Data
collection took place in Duffy Daugherty Athletic Training Room at Michigan State
University.

Each subject was given a tutorial on static and dynamic stretching prior to
completing the study. All participants were required to attend 2 testing sessions each
lasting approximately 30 min. Dominant arm was determined by the arm athletes use to
throw a baseball/softball or attack a volleyball. I

3.6.1 SESSION 1

Participants were randomly assigned to either a static or dynamic group prior to
the start of session 1. Baseline testing was done for range of motion (shoulder extension,
shoulder flexion, shoulder internal rotation, and shoulder external rotation) and peak

torque using a goniometer and the biodex, respectively. In this study, shoulder extension

43

was measured with the patient lying prone, arm at side, and head facing away from the
shoulder being tested. The elbow was slightly bent and the palm will be facing towards
the body. The goniometer’s fulcrum was aligned lateral to the acronrion process, the
stationary arm was aligned parallel to the table top, and the moving arm was aligned with
the midline of the lateral humerus. The patient was instructed to the lift their arm off the
table as far as they can. The normal range of motion for shoulder extension is 40 to 60
degrees.

Shoulder external rotation was measured with patient lying supine, elbow flexed
to 90 degrees. The goniometer’s fulcrum was centered on the olecranon process, the
stationary arm perpendicular to the floor or parallel to the table top, and the moving arm
was centered over the long axis of the ulna. The patient was instructed to rotate their arm
up as far as possible. The normal range of motion for shoulder external rotation is 80 to
100 degrees.

Shoulder flexion was measured with the patient lying supine, arm at side, and
palm facing the body. The goniometer’s fulcrum was aligned lateral to the acromion
process, the stationary arm was aligned parallel to the table top, and the moving arm was
aligned with the midline of the lateral humerus. The patient was instructed to the lift their
arm over their over, making sure the keep the palm of their hand facing toward their
body. The normal range of motion for shoulder flexion is 160 to 180 degrees.

Shoulder internal rotation was measured with patient lying supine, elbow flexed
to 90 degrees. The goniometer’s fulcrum was centered on the olecranon process, the
stationary arm perpendicular to the floor or parallel to the table top, and the moving arm

was centered over the long axis of the ulna. The patient was instructed to rotate their arm

down as far as possible. The normal range of motion for shoulder internal rotation is 60
to 80 degrees.

Peak torque measurements were taken with the shoulder in internal and external
rotation in the modified neutral position (seated). The dynarnometer orientation was at 20
degrees, the dynamometer tilt was 50 degrees, the seat orientation was 15 degrees, and
the seatback tilt was 55-85 degrees. The axis alignment was longitudinal through the head
of the shaft of the humerus in a horizontal plane. The ready position was full external
rotation. Following the static or dynamic stretching intervention post-testing
measurements was acquired again for range of motion and peak torque.

3.6.2 SESSION 2

Baseline testing was done for range of motion and peak torque as in Session 1
using a goniometer and the biodex, respectively. Following the static or dynamic
stretching intervention post-testing measurements was acquired for range of motion and
peak torque.

3.6.3 STATISTICAL ANALYSIS

Means and standard deviations was calculated for descriptive statistics. Each
dependent variable (i.e., shoulder flexion, shoulder extension) in this study was analyzed
separately. Data was analyzed using a 2 stretch condition (static vs. dynamic) x 2 testing
occasion (pre vs. post) analysis of variance (ANOVA) with repeated measures on the last
factor. The level of significance was set at p S .05 and all analyses were conducted using

SPSS version 17.1 for Windows (SPSS Inc., Chicago, IL).

45

CHAPTER 4
RESULTS

The primary purpose of this study was to investigate whether a static or dynamic
stretching protocol is more effective at the shoulder complex as measured by range of
motion and peak torque. The two major hypotheses were: a) dynamic stretching will
produce greater range of motion at the shoulder complex than static stretching, and b)
dynamic stretching will produce greater peak torque at the shoulder complex than static
stretching. For clarity, the results section is separated into subject demographics, flexion
range of motion, extension range of motion, internal rotation range of motion, external
rotation range of motion, peak torque away (fiom external rotation to internal rotation)
and peak torque towards (from internal rotation to external rotation).
4.1 SUBJECT DEMOGRAPHICS

A total of 60 NCAA Division I athletes volunteered to participate in the study.
There were nine male athletes (age =19.56 i 0.86 years, 72.22 i: 1.66 inches, 196.33 i
13.75 lbs.) and 21 female athletes (20 :t 0.916 years, 66.86 i 3.52 inches, 150.31 i 20.16
lbs.). All were healthy individuals with no self-reported surgery on their dominant arm
within the last 6-months or no previous injury to their dominant arm, elbow, wrist, or
hand 1 month prior to the study. Athletes had a total of 2.02 i .81 years experience
playing at MSU and 11.92 i 3.01 years experience playing their respective sport. The
majority of athletes were right arm dominant (26/30=86.7%). Over half the athletes
participated in softball (n=17, 57%) followed by baseball (n=9, 30%) and volleyball

(n=4, 13%). Player positions can be found in Table 4-1.

46

Table 4-1: Player Positions for Baseball, Softball, and Volleyball

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Softball Baseball Volleyball

Catcher 3 3

Center Fielder 1

First Base 1

Left Fielder l

Outfield 4 2

Pitcher 4 2

Second Base 1

Shortstop 1

Third Base 1

Utility 1 1

Libero 1
Right Side 1
Setter 2
Total 17 9 4

 

 

 

 

4.2 RESULTS FOR SHOULDER RANGE OF MOTION AND PEAK TORQUE
Athletes participated in two sessions that included a static stretching protocol and
a dynamic stretching protocol. Baseline range of motion testing was performed using a
goniometer for shoulder extension, shoulder flexion, shoulder internal rotation, and
shoulder external rotation. In addition to range of motion, athletes also performed a

biodex test for peak torque which included measurements for both away (shoulder

47

 

moving fi'om external rotation to internal rotation) and towards (shoulder moving fi'om
internal rotation to external rotation).

4.2.1 SHOULDER FLEXION

The normal range of motion for shoulder flexion is 160 to 180 degrees. A
repeated measure ANOVA was conducted to determine flexion range of motion in
stretching conditions (static vs dynamic) and testing occasions (pre vs post). Athletes
demonstrated significant differences within the testing occasions (F ( 1,58) = 110.46, p <
.00) (see Tables 4-2, 4-3). Pairwise comparisons revealed significant differences between
the pre stretch and post stretch (p <.00). Specifically, when athletes performed either the
static stretch or the dynamic stretch they significantly increased their flexion range of
motion fiom pre to post test. There were no significant differences between the static and
dynamic stretching (F(1,58) = .28, p = .60) or the interaction between testing and
stretching (F(1,58) = .85, p = .36).

Table 4-2: Descriptive Statistics for Flexion Range of Motion for Stretching
Conditions and Testing Occasions

 

 

 

 

Flexion N Mean Std. 95% 95%
Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 180.10 1 4.326 178.444 181.756
Post 30 184.23 1: 3.989 182.688 185.799
Dynamic
Pre 30 181.00 :3; 4.727 179.344 182.656
Post 30 184.47 : 4.455 182.921 186.012

 

 

 

 

 

 

48

 

Table 4-3: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

Effect Wilk’s Lambda Df F p
Testing .344 1 1 10.46 .000*
Testing X Stretching .986 1 .850 .360

 

 

 

 

 

 

 

*(significant at the p = .05 level)

4.2.2 SHOULDER EXTENSION

The normal range of motion for shoulder extension is 45 degrees. A repeated
measure ANOVA was conducted to determine extension range of motion in stretching
conditions (static vs dynamic) and testing occasions (pre vs post). Athletes exhibited
significant differences within the testing occasions (F ( 1,58) = 9.31, p = .003) (see Tables
4-4, 4-5). Post-hoc pairwise comparisons revealed significant differences between the pre
stretch and post stretch (p =.003). Regardless of the stretching protocol, athletes
significantly increased their extension range of motion fi'om pre to post test. However,
there were no significant differences between the static and dynamic stretching (F(1,58) =

.21, p = .65) or the interaction between testing and stretching (F(1,58) = 1.31, p = .26).

49

Table 4-4: Descriptive Statistics for Extension Range of Motion for Stretching
Conditions and Testing Occasions

 

 

 

 

Extension N Mean Std. 95% 95%
Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 69.37 i 6.071 67.035 71.698
Post 30 70.70 i 6.706 68.269 73.131
Dynamic
Pre 30 67.87 3; 6.673 65.535 70.198
Post 30 70.80 i 6.599 68.369 73.231

 

 

 

 

 

 

Table 4-5: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

 

 

 

 

Effect Wilk’s Lambda df F P
Testing .862 1 9.3 13 .003*
Testing X Stretching .978 1 1.310 .257

 

 

 

*(significant at the p = .05 level)

4.2.3 SHOULDER EXTERNAL ROTATION

The normal range of motion for shoulder external rotation is 80 to 100 degrees for

normal non-athletes. Generally, athletes that participate in overhead sports tend to have a

higher range of motion for external rotation. A repeated measure ANOVA was conducted

to determine external rotation range of motion in stretching conditions (static vs dynamic)

and testing occasions (pre vs post). As expected, athletes demonstrated significant

differences within the testing occasions (F( 1,58) = 30.24, p < .00) (see Tables 4-6, 4-7).

Further, pairwise comparisons revealed athletes significantly increased their external

rotation range of motion from pre stretch to post stretch (p <.00). There were no

50

 

 

significant differences between the static and dynamic stretching (F(1,58) = .31, p = .58).
However, the interaction between testing and stretching was found to be significant for
external rotation (F(1,58) = 4.05, p = .049).

Table 4-6: Descriptive Statistics for External Rotation Range of Motion for
Stretching Conditions and Testing Occasions

 

 

 

 

External N Mean Std. 95% 95%
Rotation Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 111.23 1 7.394 108.530 113.937
Post 30 112.97 : 8.503 108.597 114.03
Dynamic
Pre 30 111.30 1: 7.401 110.048 115.886
Post 30 115.03 3: 7.435 112.114 117.952

 

 

 

 

 

 

Table 4-7: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

Effect Wilk’s Lambda df F P
Testing .657 1 30.241 .000*
Testing X Stretching .935 1 4.048 0.049*

 

 

 

 

 

 

 

*(significant at the p = .05 level)
4.2.4 SHOULDER INTERNAL ROTATION
The normal range of motion for shoulder internal rotation is 55 degrees.
Consistent with all other data analysis for range of motion, a repeated measure ANOVA
was conducted to determine internal rotation range of motion in stretching conditions
(static vs dynamic) and testing occasions (pre vs post). Athletes demonstrated significant

differences in internal range of motion (F(1,58) = 8.96, p = .004) (see Tables 4-8, 4-9).

51

 

Post-hoe analysis revealed collegiate athletes significantly increased their internal
rotation from pre stretch to post stretch (p =.004). There were no significant differences
between the static and dynamic stretching (F (1,58) = .71 , p = .40) or the interaction
between testing and stretching (F(1,58) = .000, p = .99).

Table 4-8: Descriptive Statistics for Internal Rotation Range of Motion for
Stretching Conditions and Testing Occasions

 

 

 

External N Mean Std. 95% 95%
Rotation Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 47.43 ' 1 10.510 43.680 51.187
Post 30 50.53 1 10.523 45.713 53.220
Dynamic
Pre 30 49.47 _‘I_'_ 10.027 46.901 54.165
Post 30 52.53 i 9.317 48.901 56.165

 

 

 

 

 

 

 

Table 4-9: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

Effect Wilk’s Lambda df F P
Testing .866 1 8.955 .004*
Testing X Stretching 1.000 1 .000 0.987

 

 

 

 

 

 

 

*(significant at the p = .05 level)
4.2.5 SHOULDER PEAK TORQUE AWAY
Collegiate athletes performed a biodex test to measure peak torque away, which is
defined as the shoulder moving from external rotation to internal rotation. A repeated
measure AN OVA was conducted to determine peak torque away in stretching conditions

(static vs dynamic) and testing occasions (pre vs post). No significant differences were

52

 

noted within the testing occasions (F(1,58) =0.05, p = 0.82) (see Tables 4-10, 4-11). In
addition, athletes did not exhibit significant differences between the static and dynamic
stretching (F(1,58) = .01 , p = .92) or the interaction between testing and stretching (F(1,58)
= 0.02, p = .90).

Table 4-10: Descriptive Statistics for Peak Torque Away for Stretching Conditions
and Testing Occasions

 

 

 

 

Peak Torque N Mean Std. 95% 95%
Away Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 33.90 : 14.378 28.960 38.840
Post 30 33.70 : 12.598 28.760 38.640
Dynamic
Pre 30 34.23 : 13.408 29.413 39.054
Post 30 33.80 _+_ 12.971 28.979 38.621

 

 

 

 

 

 

Table 4-11: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

Effect Wilk’s Lambda df F P
Testing .999 l .051 0.823
Testing X Stretching 1.000 1 .015 0.904

 

 

 

 

 

 

 

*(significant at the p = .05 level)
4.2.6 SHOULDER PEAK TORQUE TOWARDS
Finally, athletes performed a biodex test for peak torque towards which was
defined as their shoulder moving from internal rotation to external rotation. A repeated
measure ANOVA was conducted to determine peak torque towards in stretching

conditions (static vs dynamic) and testing occasions (pre vs post). No significant

53

 

 

differences were found for testing occasions (F(1,58) = 2.07, p = .16) (see Tables 4-12, 4-

13), the interaction between testing and stretching (F(1,58) = .1.89, p = .18), or between

static and dynamic stretching (F(1,58) = .04, p = .84).

Table 4—12: Descriptive Statistics for Peak Torque Towards for Stretching

Conditions and Testing Occasions

 

 

 

 

Peak Torque N Mean Std. 95% 95%
Towards Deviation Confidence Confidence
Interval Interval
Lower Upper
Static
Pre 30 18.50 3; 9.609 14.935 22.065
Post 30 19.97 i 8.520 16.135 23.265
Dynamic
Pre 30 19.70 i 9.900 16.615 23.319
Post 30 19.73 i 9.780 16.381 23.085

 

 

 

 

 

 

Table 4-13: AN OVA Comparing Stretching Conditions and Testing Occasions

 

 

 

 

 

 

 

 

Effect Wilk’s Lambda df F P
Testing .966 1 2.068 0.156
Testing X Stretching .968 1 1.889 0.175

 

 

*(significant at the p = .05 level)

54

 

CHAPTER 5
DISCUSSION

The primary purpose of this study was to investigate whether a static or dynamic
stretching protocol is more effective at the shoulder complex as measured by range of
motion and peak torque. It was hypothesized that dynamic stretching would produce
greater range of motion at the shoulder complex than static stretching. In addition, it was
also hypothesized that dynamic stretching would produce greater peak torque at the
shoulder complex than static stretching. The discussion section is organized into six
subsections. These include: a) range of motion at the shoulder complex following static
and dynamic stretching, b) peak torque at the shoulder complex following static and
dynamic stretching, c) utilization and clinical implications for static and dynamic
stretching, d) limitations of current study, e) future research implications, and f)
conclusions.
5.1 RANGE OF MOTION AT THE SHOULDER COMPLEX FOLLOWING
STATIC AND DYNAMIC STRETCHING

The current study’s finding revealed collegiate athletes significantly increased
their shoulder flexion range of motion from pre-stretching to post-stretching. However,
flexion at the shoulder complex was not differentially influenced by either a dynamic
stretching or a static protocol. In other words, one stretching protocol did not produce
significantly greater gains over the other stretching protocol. Similar to flexion, extension
at the shoulder complex was not influenced any more by using a dynamic stretching

protocol versus a static protocol. Although, collegiate athletes did have significant gains

55

in extension range of motion after stretching, neither the static nor dynamic stretching
protocol was more effective.

The findings from the current study did reveal an interaction between the
stretching protocols and time (i.e., time pre to post stretch) for external rotation.
Specifically, collegiate athletes demonstrated significantly greater range of motion on
external rotation after performing a dynamic stretching protocol when compared to a
static stretching protocol. This finding may be relevant to baseball players who need a
greater range of motion when pitching in order to produce greater velocity. According to
Crockett et al. (2002) throwing shoulders in pitchers frequently exhibit excessive external
rotation. In this study, Crockett and colleagues (2002) examined glenohumeral joint
range of motion of the dominant vs. non-dominant shoulder in 25 professional pitchers
(throwing group) and 25 non-throwing subjects. External rotation, humeral head
retroversion, and glenoid retroversion in the dominant shoulder of the throwing group
were significantly greater than the non-dominant shoulder. In the non-throwing group
there was no significant difference in external rotation, humeral head retroversion, or
glenoid retroversion between dominant and non-dominant shoulders. When comparing
the throwing group vs. the non-throwing group, external rotation was also significantly
greater (Crockett et al., 2002). This study concluded that increases in external rotation,
humeral head retroversion, and glenoid retroversion may provide a competitive edge in
pitching, because for the same amount of external rotation (which may relate positively to
pitch velocity) the arm with more humeral head retroversion places less stress on the

anterior capsule-labral structures (Crockett et al., 2002). Therefore, it can be thought of as

56

not only a protective mechanism but also a performance booster. This indicates that
dynamic stretching may be better for pitchers to perform before practice or competition.

The present study found that there were no significant differences between the
static and dynamic stretching protocol when collegiate athletes performed internal
rotation at the shoulder complex. However, collegiate athletes did significantly increase
their shoulder internal range of motion after performing both the static and dynamic
stretching protocols. The findings of this study were similar to a study by Laudner and
colleagues (2008) who found internal and external rotation were increased after sleeper
stretches (e. g. static stretches). This study only examined NCAA Division I baseball
players, while the current study used baseball, volleyball, and softball players. In
addition, a clinician performed these stretches rather than the athlete themselves.

In contrast to the above study and this study, Reinold and colleagues (2008) found
that internal and external rotation were significantly decreased after a pitching session.
Reinold et al. concluded that this decrease in range of motion after pitching lasts for 24
hours and may be a result of eccentric muscle contractions causing acute alterations in the
musculotendinous junctions at the shoulder complex. These musculotendinous
adaptations alter the range of motion available in the shoulder (Reinold, et al., 2008).
Therefore, stretching before practice or competition may not be warranted for overhead
athletes due to potential decreases in range of motion caused by eccentric activity of the
shoulder musculature. However, more research is warranted to determine if stretching is

detrimental or facilities range of motion at the shoulder complex.

57

5.2 PEAK TORQUE AT THE SHOULDER COMPLEX FOLLOWING STATIC
AND DYNAMIC STRETCHING

Peak torque away (external to internal rotation) and peak torque towards (internal
to external rotation) did not demonstrate significant gains from pre-stretching to post-
stretching with either a static or dynamic stretching protocol. The current study did not
exhibit any negative effects from the stretching protocols. This is in contrast to prior
research, which found that static stretching preceding the main strength activity
significantly decreased performance in the lower extremity (Nelson, Kokkonen, &
Amall, 2005). Similarly, Cramer and colleagues (2004) found that after static stretching,
peak torque in the leg extensors also significantly decreased. These researchers suggested
that the stretching-induced decreases in peak torque may be related to changes in the
mechanical properties of the muscle, such as an altered length-tension relationship, or a
central nervous system inhibitory mechanism (Cramer, Housh, Johnson, Miller, Coburn,
& Beck, 2004; Nelson, Kokkonen, & Amall, 2005).

Nelson and Kokkonen also found conflicting results with the current study when
athletes performed ballistic stretches. These researchers examined the effects of ballistic
muscle stretching on maximal strength performance during knee flexion and knee
extension. Ballistic stretching is similar to dynamic stretching in terms of it being an
active motion to stretch. The ballistic stretching program had a negative influence on one
repetition maximum for knee flexion and knee extension (Nelson & Kokkonen, 2001).
Although, most of the aforementioned studies utilized the lower extremity, the shoulder
complex did not produce any detrimental effects after stretching on peak torque.

Moreover, it is difficult to compare and contrast previous studies as no research to date

58

has investigated the effects of static and dynamic stretching on peak torque at the
shoulder complex.

In contrast to these aforementioned studies, other studies did not observe any
detrimental effects of stretching on strength. A study by Egan and colleagues (2006)
found that static stretching had no impact on peak torque or mean power. Eleven female
collegiate basketball players performed maximal concentric isokinetic leg extensions on a
biodex system 3 dynarnometer. After the initial testing, the dominant leg extensors were
stretched using static stretches. After completing the stretching protocol, the athletes
performed the maximal concentric isokinetic leg extension tests again. There was no
significant decrease found in peak torque or mean power. These findings indicate that the
static stretching has no impact on peak torque or mean power during maximal, voluntary
concentric isokinetic leg extension in collegiate women's basketball players (Egan,
Cramer, Massey, Laurie, & Marek, 2006).

In another study the effect of acute stretching performed prior to a strength
activity in older adults was investigated. The study examined the effect of stretching on
maximal voluntary isokinetic torque production. Participants included 15 young (19-27
yrs) and 14 older adults (62-79 yrs). Maximal voluntary isokinetic torque was measured
before and after stretching using a biodex system 3 isokinetic dynarnometer. After
stretching the participant was allowed to rest 10 minutes before the strength tests were
repeated. Results revealed no significant differences between the pre- and post-treatment
maximal voluntary torque production values (Garrison, Nelson, Welsch, & Wood, 2002).
The two previously mentioned studies are in agreement with the current study that found

static stretching has no detrimental effect on peak torque.

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Finally, Herda and colleagues (2008) examined the acute effects of static versus
dynamic stretching on peak torque, electromyographic, and mechanomyo graphic
amplitude of the biceps fernoris during isometric maximal voluntary contractions of the
leg flexors. The researchers found that peak torque decreased after the static stretching,
but did not change after the dynamic stretching. Therefore, just as the current research
study demonstrated, an acute dynamic stretching protocol is not detrimental to muscle
strength.

The difference between the previously mentioned studies and Nelson and
Cramer’s studies showing decrease in strength, was the amount of time the stretch was
maintained or performed. The recommended time for stretching is 30 to 45 seconds and it
is also optimal to perform each stretch 3 to 4 times (Bandy & Irion, 1994). The studies
that found decreases in strength typically performed the stretches for an excessive amount
of time (i.e. 1-2 min.) (Rubini, Costa, & Gomes, 2007). In the current study, the athletes
performed each stretch 3 times for 30 seconds, which is the optimal amount of time.
Therefore, this could be a potential reason for no detrimental effects on peak torque.

5.3 UTILIZATION AND CLINICAL IMPLICATIONS FOR STATIC AND
DYNAMIC STRETCHIN G

The results of this study provide athletic trainers, physical therapists, and coaches
with important information regarding overhead athletes and pre-practice or therapeutic
stretching protocols. In essence the current study demonstrates that neither stretching
protocol is better than the other except for external range of motion. In fact, in terms of
range of motion, this study illustrated that both stretching protocols had produced
significant gains, External rotation range of motion was the only motion that exhibited

greater gains with dynamic stretching over static stretching. In terms of peak torque away

60

and towards, the current findings demonstrated that there were no significant gains in
peak torque after stretching.

Coaches can rest easy knowing that whichever stretching protocol they choose
their athletes will be ready to throw or spike a ball. Numerous coaches are set on using a
static stretching protocol because it is what they are familiar with or have the most
experience using. Coaches may also believe that using a static stretching protocol can
prevent injuries, because this is what they have grown up learning. The current study
shows that it does not matter which protocol is used, except perhaps in regards to baseball
pitchers. It may be beneficial to use dynamic stretching with them over static stretching
since greater gains in external rotation range of motion were found with the dynamic
stretching. And greater external rotation has been shown to give greater velocity to
pitches.

Clinicians can use either a dynamic or static stretching protocol when bringing
their patient back from injury or surgery to play. Athletic trainers and physical therapists
are always looking for cutting edge research on what is best to return athletes to play. Just
as coaches are more familiar and more comfortable with static stretching, so are
clinicians. Static stretching is something that is taught to increase range of motion after
an injury or surgery takes place. The current study indicates that dynamic stretching
could also be used. Dynamic stretching may also be more firnctional for return to play; its
constant motion may provide more of a transition to sport specific activities like throwing
and spiking. It may also be better to utilize this type of stretching for baseball pitchers

that are returning fi'om surgery.

61

 

This information also allows the athlete to make the decision for their pre-practice
stretching routine for their shoulder. If the athlete feels that one prepares them better for
competition it may be better for them to use that stretching protocol. Athletes can be
affected by anything that they believe can affect their peak performance. This may be due
to familiarity, word of mouth, or repeated use fiom their childhood. This study shows that
either stretching protocol can be utilized with no significant difference between the two.
5.4 LIMITATIONS OF CURRENT STUDY

There are several limitations within this study. First, there were only 30 collegiate
athletes that participated in this study. Although this was an adequate sample size for the
type of study being conducted, an increase in sample size would also increase the
external validity of the study. Second, the sample size only included three collegiate
teams (ie., softball, baseball, volleyball) with softball players representing 57% of the
participants. As a result, these collegiate teams were not equally represented, and,
therefore the results may relate more to softball players than volleyball and baseball. A
third limitation to the study rs the way peak torque was measured. Peak torque was
supposed to represent the power that each athlete uses to either throw or spike a ball. This
is not a direct representation of the power used in throwing or spiking, but rather a tool to
represent these activities. Finally, only collegiate athletes were used for this study. Future
studies could concentrate on high school athletes shoulder range of motion and peak
torque.

5.5 FUTURE RESEARCH

The current study has led to the possibility of several firture studies. For example,

stretching protocols could be compared between males and females. This may determine

62

if males or females are affected differently by various stretching protocols. Another
firture study could investigate one specific population such as baseball pitchers, rather
than overhead athletes in general. Baseball pitchers are known to have increased external
rotation range of motion at the shoulder complex when compared to the general
population. Therefore, how would various stretching protocols affect their pitching
capabilities? It would also be advantageous to examine propioceptive neuromuscular
facilitation (PNF) stretching. Unlike dynamic and static stretching, PNF would involve a
clinician. PNF has been shown to give large gains in range of motion in a small amount
of time. However, it would be important to control for bias between testers (stretching
clinicians) in a study like the one suggested. Another possible research study could to
investigate sport specific performance rather than measuring peak torque using the
biodex. For example, you could measure the speed of a pitch or spike, or examine the
accuracy of a throw. Finally, future studies could investigate injury occurrences between
various stretching protocols (ie., static, dynamic, PNF).
5.6 CONCLUSIONS

Overall, this study demonstrates that there isno significant difference between
static and dynamic stretching protocols at the shoulder complex when performing range
of motion or peak torque. The one exception is external rotation range of motion. The
dynamic stretching protocol demonstrated significantly greater gains in range of motion
than the static stretching protocol for external rotation. This greater significant increase in
external rotation with the dynamic stretching protocol is relevant for baseball pitchers
who need the greater external rotation to make gains in velocity. Results of this study will

allow coaches and clinicians to use either stretching protocol for practice or competition

63

warm-ups and return to play protocols. It will also allow them to consider trying dynamic
stretching for baseball pitchers. For athletes, this study indicates that they can use either
stretching protocol to increase range of motion and have no significant effect on their

torque output.

64

APPENDIX A

HEALTH HISTORY QUESTIONNAIRE

65

Health History Questionnaire

 

 

 

 

 

Name Date
Gender: M F Age
Height Weight
Sport Position

 

 

Years you have played current sport

 

Years you have played on MSU’s NCAA Team

 

Dominant arm used to throw, pitch, or spike a ball

 

Have you had surgery on your dominant arm within the last 6 months? Y N

List any injury to your dominant arm, elbow, wrist, or hand one month prior to
participating in this study

 

 

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APPENDIX B

INFORMED CONSENT FORM

67

The Effects of Static and Dynamic Stretching on Range of Motion and Performance

Informed Consent
For questions regarding this study, For questions regarding your rights
Please contact: as a research participant, contact:
Dr. Tracey Covassin, ATC Michigan State University
Department of Kinesiology Human Research Protection Program
Michigan State University 207 Olds Hall
Phone: 517.353.2010 East Lansing, MI 48824
E-mail: covassin@ath.msu.edu Phone: 517.355.21 80

Fax: 517.432.4503

Katie M. Rapking, ATC E-mail: irb@msu.edu
Graduate Assistant
Michigan State University

Phone: 513.218.1828
E-mail: rapkingk@msu.edu

The purpose of this study is to investigate whether a static or dynamic stretching protocol
is more effective at the shoulder complex as measured by range of motion and peak torque. The
study will use a goniometer to measure range of motion and a Biodex system 3 dynarnometer to
measure peak torque pre and post test.

If you have had surgery on your dominant arm within the last six months you will be
excluded from this study. If you have had an injury to your dominant arm, elbow, wrist, or
hand within the last month, you will also be excluded from this study.

Your participation in this study will require two testing sessions (approximately 30
minutes each session) on separate days. Upon your first session arrival to the MSU Athletic
Training Research Laboratory, you will be presented with an overview of the study, voluntarily
sign a consent form, and complete a health history questionnaire. You will then be given a verbal
and visual tutorial on either the static stretching protocol or the dynamic stretching protocol being
studied for this research. Once you feel comfortable with the protocol, your shoulder range of
motion (flexion, extension, internal rotation and external rotation) will be measured as well as
your peak torque. Each stretching protocol will consist of four stretches that will be performed 3
times for 30 seconds. Following the stretching protocol post-test measurements will be taken for
range of motion and peak torque.

The second session will also be performed at MSU’s Athletic Training Research
Laboratory. You will be given a verbal and visual tutorial on either the dynamic stretching
protocol or the static stretching protocol. When you feel comfortable with the protocol, baseline
measurements will again be taken for range of motion and peak torque. You will then perform the
stretching protocol. Each of the four stretches will be performed 3 times for 30 seconds.
Following the stretching protocol post-test measurements will be taken for range of motion and

peak torque.

It is impossible for the risk of injury to be completely eliminated during physical activity.
The risk associated with this study may be minimal delayed onset muscle soreness from
performing the stretches and measuring of peak torque. Measures will be taken during the test to
ensure your safety throughout the research protocol. A certified athletic trainer will be on-site at

68

all times during the testing session. Ifthere is any point during the testing procedures when you
feel that you cannot continue, please let the investigator know and the test will be terminated.

The benefits that come from your participation will help further advancements in
determining which stretching protocol is more appropriate for upper extremity sports to use prior
to practice or competition. This could potentially lead to firrther advancements in the sports of
softball, baseball, and volleyball. The results of this test will be provided to you at the conclusion
of the session.

Participation in this research project is completely voluntary. You have the right to say
no. You may change your mind at any time and withdraw. You may choose not to answer
specific questions or to stop participating at any time. Your identity and information
recorded during the study will remain confidential. Confidentiality will be protected by;

(a) results will be presented in aggregate form in any presentations and publications; and

(b) all data will be stored in a computer that has a password necessary to see confidential

data. Data will be stored under double lock and key, whereby only the investigators and

their agents will have access. Confidentiality will be protected to the maximum extent allowable
by law. Your participation in this research project will not involve any additional costs to you or
your health care insurer. You will not receive money or any other form of compensation for
participating in this study.

If you are injured as a result of your participation in this research project,
Michigan State University will assist you in obtaining emergency care, if necessary, for
your research related injuries. If you have insurance for medical care, your insurance
carrier will be billed in the ordinary manner. As with any medical insurance, any costs
that are not covered or are in excess of what are paid by your insurance, including
deductibles, will be your responsibility. The University’s policy is not to provide
financial compensation for lost wages, disability, pain or discomfort, unless required by
law to do so. This does not mean that you are giving up any legal right you may have.
You may contact Dr. Tracey Covassin at 517.353.2010 with any questions or to report an

my ury.

If you have concerns or questions about this study, such as scientific issues, how to do
any part of it, or to report an injury, please contact the researcher (Katie M. Rapking, Jenison
FieldHouse, East Lansing, MI, 48824, rapkingk@msu.edu, 513.218.1828 or Dr. Tracey Covassin
105 [M Sport Circle, East Lansing MI 48824, covassin@msu.edu. 517.353.2010).

Ifyou have questions or concerns about your role and rights as a research participant,
would like to obtain information or offer input, or would like to register a complaint about this
study, you may contact, anonymously if you wish, the Michigan State University’s Human
Research Protection Program at 517-355-2180, Fax 517-432-4503, or e-mail irb@msu.edu or
regular mail at 207 Olds Hall, MSU, East Lansing, MI 48824.

Your signature below indicates your voluntary agreement to participate in this study.

 

 

 

I, , have read and agree to participate in
(Please Print Your Name)
this study as described above.
/ /
(Please Sign Your Name) (Date)

69

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70

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