w? m l/ll/////I////lI///I////lllll/I/I/lx/lI/[l/l/lljlll L LEE-RM RY Michigan: §¢aw University *2' THESIS This is to certify that the thesis entitled THE EFFECTS OF WATER IMMERSION AND LEVEL OF EXHALATION UPON BODY DENSITY ANALYSIS presented by Craig S. Vossekuil has been accepted towards fulfillment of the requirements for degreein Physical Education ZZZ/Z Mummmmaun DateW/V 0-7639 O OVERDUE FINES: 25¢ per day per itel BEJURNING LIBRARY MATERIALS: Place in book return to remove charge from circulation records THE EFFECTS OF WATER IMMERSION AND LEVEL OF EXHALATION UPON BODY DENSITY ANALYSIS BY Craig S. Vossekuil A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department of Health, Physical Education and Recreation 1981 ABSTRACT THE EFFECTS OF WATER IMMERSION AND LEVEL OF EXHALATION UPON BODY DENSITY ANALYSIS BY Craig S. Vossekuil The purpose of this study was to determine the effects of immersion in water upon residual volume and body density calculation and to compare the effects of level of exhalation upon body density calculation. Thirty-five normal, healthy males, 18-28 years of age, served as subjects. A sequence of five measurements of lung volume were determined: predicted residual volume, residual volume in air, residual volume while immersed to the neck in water, and end-tidal volume while fully submerged in water. The underwater weight of each subject was recorded simultane- ously with the latter two measurements, and calculations of body density were made for each of the five conditions. There were statistically significant differences (p<.01) between the criterion procedure for measuring body density (exhaling maximally while fully submerged in water) and all other procedures except one: there was no significant differ- ence between the criterion procedure and the procedure using end-tidal lung volume. It is apparent that the determination Craig S. VOssekuil of body density using end-tidal lung volume is a valid alter- native to the criterion procedure. To my parents ii ACKNOWLEDGMENTS Were it not for the work of others in generating and transmitting knowledge, the wheel would be continually rein- vented: we stand on the shoulders of giants. Among the tallest of these are Dr. W. D. VanHuss and Dr. W. W. Heusner, to whom I am indebted for assisting with this paper and for setting high standards of performance. Thanks also to Mr. Bob Wells for the generous donation of his time, which is limited, and his technical expertise, which is not, and to Bill, Bruce, and Homer for their help in data collection. iii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . Chapter I. INTRODUCTION TO THE PROBLEM. . . . . . Purpose of the Study . . Research Hypotheses. . . Research Plan. . . . . Definition of Terms. . . Residual Volume . . . . . . . . Functional Residual Volume. . . . . Hydrostatic Weighing. . . . . . . Body Composition . . . . . . . . Body Density . . . . . . . . . II. REVIEW OF THE LITERATURE. . . . . . . The Effect of Water Submersion on Residual Volume . . . . . A Review of the Methods for Determining Residual Volume . The Effect of the Level of Expiration on Body Composition Measurement . . . . III. RESEARCH METHODS . . . . . . . . . Subjects . . . . . Measurement Procedures. . . . . . . Underwater Weight. . . . . . . . Lung Volume. . . . . . . . . . Test Procedures . . . . . . . . . Residual Volume in Air . . . . . Residual Volume While Immersed to the Neck in Water . . . Residual Volume While Fully Submerged in Water . . - End-Tidal Volume While Fully Submerged in Water . . . . . . . . . . Statistical Analysis . . . . . . . iv Page vi UlU'lU'lU1U'I ()1wa l-' 0‘ 11 11 11 11 12 13 13 14 14 15 15 Chapter Page IV. RESULTS AND DISCUSSION . . . . . . . . 17 Residual Volume. . . . . . . . . . 17 Percent Fat . . . . . . . . . . . 18 Discussion . . . . . . . . . . . 20 V. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS . . 22 Summary . . . . . . . . . . . . 22 Conclusions . . . . . . . . . . . 23 Recommendations. . . . . . . . . . 24 APPENDICES Appendix A. BaSiC Data 0 o o o o e o o o o o o 25 B. Formulas. . . . . . . . . . . . . 26 C. Test Instrument, Schematic Diagram of . . . 27 BIBLIOGRAPHY. . . . . . . . . . . . . . 28 Table 4.1. LIST Statistical Results, Volume . . . . Statistical Results, Volume . . . . Statistical Results, Statistical Results, Fat 0 O O O I Correlation, Percent OF TABLES Page Descriptive, Residual O O O O O O O O O 18 Significance, Residual O O O O O O O I O 18 Descriptive, Percent Fat. 19 Significance, Percent O O O O O O O O O 19 Fat. 0 O O O O O O 19 vi CHAPTER I INTRODUCTION TO THE PROBLEM In physiological research concerned with the effects of such variables as exercise and diet, it is often of interest to determine the effects of these stresses on body composi- tion. Measurements of body composition permit the estimation of body fat and fat-free weight. When these components of body composition are in the proper proportion to each other both sports performance and healthful living in general are enhanced. Obtaining an accurate estimation of body composition is not easily accomplished. The approach most commonly used to obtain such an estimation is hydrostatic weighing. In this method the precision with which one can estimate body composi- tion is dependent upon obtaining accurate measures of under- water body weight and of the residual volume of air in the lungs at the time of weighing. Most underwater weighing systems are suspension systems whereby the subject is lowered underwater by means of a hoist. The subject then exhales maximally, at which time the underwater weight is quickly observed, and the residual volume of air is measured. Care must be taken with this system, however, to obtain the needed accuracy. Water turbulence, pendulum action created by lowering the chair into the water, and movement of the subject in the chair (some of which may be unavoidable due to the necessity for the subject to exhale maximally) can all create sufficient scale oscillations to preclude any reasonable chance of obtaining an accurate reading. The present study is intended to examine ways of simplify- ing the measurement of lung volume at the time of underwater weighing, with the goal of reducing operator error associated with body composition measurement. This could conceivably be accomplished in two ways. First, the subject could be allowed to exhale normally to end-tidal volume, rather than exhaling maximally to residual volume. This would minimize movement of the chair and scale oscillation and maximize the time for the operator to evaluate the underwater weight. Second, residual volume could be measured under ordinary environmental conditions (in air) or with the subject immersed in water up to the neck. If one of these measures of residual volume were found to be a sufficiently accurate estimation of residual volume while submerged, it could be used in subsequent cal- culations of body composition, which would simplify procedures for obtaining a measure of underwater weight. Few studies have been conducted comparing estimates of body composition using lung volumes following maximal expira- tion with estimates obtained using lung volumes following partial expiration, and those that have been done show conflicting results. Some show that it makes no difference what volume of air remains in the lungs at the time the under- water weight is observed (4,12); others show body density to be lower at full expiration than at one-half full expiration (l9). Similarly, findings differ in studies comparing residual volume measured in air with residual volume measured while immersed. Some investigators found decreases in residual volume when immersed (1,2,11); some found increases (9); some found no difference (3,5,7,15,18); and others have found both increases and decreases depending upon the age of the subject (13). The present study is intended to offer new information in this area. Purpose of the Study To determine the effects of immersion in water (either immersion to the neck or full submersion) upon residual volume and to compare the effects of the level of exhalation (either end-tidal or maximal) upon body density calculation. Research Hypotheses The present investigation was designed to test the follow- ing hypotheses: 1. There is no difference between residual volume measurements made with subjects fully submerged in water and those made under ordinary environmental conditions (in air) or while immersed to the neck. Predicted residual volume, based upon subjects' height, weight, and age, will not differ from residual volume measured with the subjects submerged in water. Body density calculations will not differ, regard- less of whether lung volume is measured following maximal or end-tidal exhalation. Research Plan Five body density calculations were made on each of 35 subjects using the lung volume taken under the conditions noted below: 1. 5. Residual volume under ordinary environmental con- ditions (in air). Residual volume while immersed to the neck in water. Residual volume while fully submerged. Predicted residual volume, based on subjects' age, height, and weight. End-tidal volume while fully submerged. The residual volume was determined using the procedures originally outlined by Lundsgaard and VanSlyke (14), modified by Rahn, Penn, and Otis (16), and validated further by Sloan and Bredell (18). Body density was calculated as described by Buskirk (4). The Siri formula was used for the determina- tion of percent fat (17). Data analyses were accomplished using dependent t-tests and Pearson product-moment correlations. Definition of Terms Residual Volume The volume of air remaining in the lungs following a maximal exhalation. Functional Residual Volume The volume of air remaining in the lung following a normal exhalation (end-tidal volume). Hydrostatic Weighing A technique used to determine body composition whereby a subject is weighed while fully submerged in water. Adjust- ments necessarily must be made in subsequent calculation of body density for the volume of air remaining in the lungs. Body7Composition The division of body constituents into its components of body fat and lean body mass. Body Density A measure of weight per cubic centimeter of the body, which varies with the relative contributions of body fat and lean body mass. CHAPTER II REVIEW OF THE LITERATURE The literature which is related to this study has been subdivided into the following three sections: (a) the effect of water submersion on residual volume, (b) a review of the methods for determining residual volume, and (c) the effect of the level of expiration on body composition measurement. The Effect of Water Submersion on on Residual Volume The principle of Archimedes states that a body immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body. Because the amount of fluid displaced will vary with the amount of air that is in the lungs, it becomes critical in the calculation of body density to know the volume of air that is in the lungs at the time the underwater weight is recorded. Accordingly, most investigators obtain a simultaneous measurement of underwater weight and residual volume while the subject is completely submerged in water. Problems with operator error and subject discomfort exist with this method, however, and therefore it is of interest to determine the neces- sity of obtaining a measurement of residual volume while fully submerged in water vis a vis obtaining that measurement under ordinary environmental conditions (in air) or with the subject immersed to the neck. Few studies have been conducted comparing residual volume values collected when subjects were fully submerged in water with residual volume values collected in air. Several studies, however, have compared residual volume values in air with those obtained while the subject was immersed in water to the neck, but these studies show conflicting results. Some investigators have found no significant differences in residual volume when measured in air as when measured With the subject immersed to the neck in water (5,7,15). Sloan and Bredell (18) and Brozek, Henschel, and Keys (3) observed distinct, though not quite significant, decreases in residual volume with subjects immersed to the neck and fully submerged, respectively. Other researchers have found significant decreases in residual volume as a result of immersion to the neck in water (1,2,11). Some report an increase in residual volume (9) or both increases and decreases depending upon the age of the subject (13). While there has been a lack of uniformity in these find- ings, most authors are consistent in finding that the magnitude and the direction of the difference between residual volume while immersed and residual volume in air varied considerably between individuals. This suggests that the magnitude and direction of these variations are due to an interplay of factors. As these factors vary in importance between indi- viduals, measured residual volume will be greater or lesser when submerged than when measured in air. Among those suggested are psychological factors, such as fear and apprehension of the subject, which might inhibit exhalation and result in increased residual volume (3); hydrostatic pressure on the chest wall, resulting in greater exhalation and decreased residual volume (3); greater pressure on the lower limbs than on the chest wall, leading to vascular engorgement and stiffness of lung tissue, trapped air in alveoli, and an increased residual volume (9). A Review of the Methods for Determining Residual Volume Modifications of two basic methods for indirect measure- ment of residual volume have been employed in body density research; the open-circuit method originally developed by Darling, Cournand, and Richards (8), and the closed-circuit method reported by Lundsgaard and VanSlyke in 1918 (14). In the open-circuit approach, the subject inspires pure oxygen for a period of up to seven minutes. The expired air is collected, and when all of the nitrogen has been washed out of the lungs, the volume of expired air is noted, a sample is drawn for analysis, and residual volume is calculated. The closed-circuit method developed by Lundsgaard and VanSlyke consists of having a subject exhale maximally and then take 4-5 fairly deep respirations from a rubber bag filled with 3-4 liters of oxygen. A percentage equilibrium between the air in the lungs and the air in the bag is reached; a sample from the bag is analyzed for its nitrogen percentage; and the residual volume can then be calculated. In 1948, Rahn, Penn, and Otis found that equilibrium is established between the gases in lung and the gases in a 2-liter rebreathing bag after the third breath, rather than the fourth or the fifth (16). Further, they showed that the value for nitrogen content in normal alveolar air prior to the inhalation of oxygen is more properly 80%, rather than 79.1. The present investigation uses the Rahn modification of the Lundsgaard and VanSlyke closed-circuit method. This method has consistently been shown to be highly reliable and valid (18,20,21), and it minimizes the time needed per deter— mination. The Effect of the Level of Expiration on Body Composition Measurement Among those factors suggested as reasons for some indi- viduals having smaller residual volumes when submerged, others largers, are psychological factors, viz. anxiety and appre- hension while exhaling maximally under water. Although it has been customary that subjects should exhale maximally, the amount of air in the lungs at the time of measurement should theoretically not influence the calculation of body density. That is, as long as the volume of air in the lungs was known, it would be accounted for in the subsequent calculation of 10 body density. If this were indeed the case, it would be possible to eliminate much of the individualistic tendency mentioned above by performing hydrostatic weighing at less than full expiration; the subject would be allowed greater comfort, psychological factors would be minimized, and the Operator would have more time to accurately assess the under- water weight. Buskirk (4) cited Carlson and Chen (unpublished) as finding that as long as residual volume was measured, it made no difference what volume of air remained in the lungs at the moment the underwater weight was observed. Keys and Brozek (12) also found close agreement in body composition at full expiration and at moderate expiration in repeated trials in the same men. welch and Crisp (19), on the other hand, found body density at full expiration to be lower than at one-half full expiration. CHAPTER III RESEARCH METHODS The present study was undertaken to investigate differ- ences in body density when lung volume is measured as follows: (a) residual volume measured in air, (b) residual volume measured with the subject immersed up to the neck in water, (c) residual volume measured with the subject fully submerged, (d) end-tidal volume measured with the subject fully submerged, and (e) predicted residual volume. Subjects Thirty-five normal, healthy males ranging in age from 18-28 years (mean age = 20.9) volunteered as subjects for the study. None was either grossly obese or emaciated. Measurement Procedures Underwater Weight Measurement of underwater weight was made using a suspen- sion system whereby the subject sat in a metal chair that was lowered by a hoist to a depth such that his head was approxi- mately one inch underwater. A Sanborn recorder (Model 60—200), coupled with a Sargent recorder (Model SR), was used to record the output of a ZOO-lb load capacity strain gauge. The scales 11 12 were sufficiently damped to eliminate artifact yet retain adequate sensitivity to measure underwater weight within thirty grams. Final calibration of the scales was accomplished by attaching the rebreathing bag assembly to the metal chair, sealing the mouthpiece with tape, submerging the chair to a depth such that a subject would be completely submerged, and then readjusting the zero point on the recorder. Lung Volume Ninety-nine point eight percent pure oxygen was passed through a spirometer to saturate the gas with water vapor and to bring it to room temperature and pressure. Then, using a one-liter syringe coupled with a three-way valve, two liters of the gas were withdrawn from the spirometer and introduced into a rebreathing bag assembly. The rebreathing bag assembly was portable and consisted of a mouthpiece and three-way valve, branching off to a breathing tube open to room air and a breathing tube leading to a two-liter rubber rebreathing bag. The dead space in the tubing and three-way valve was deter- mined to be 72.5 ml by means of water displacement. The water displacement method was also used to calibrate the one-liter syringe. The spirometer, connective tubing, syringe, and rebreathing bag were thoroughly flushed with 02 prior to introducing the 02 used for determination of lung volume. After the sample was taken, the rebreathing bag was immediately transported to an adjoining room and analyzed for content of the gas. Determinations of percent CO2 and 02 13 were accomplished simultaneously by using the Beckman LB-Z and OM-ll analyzers, respectively. The percentages were added together and subtracted from 100% to give percent N2. The gas analyzers were adjusted to the zero points by the use of compressed helium. Using a Haldane chemical analyzer oxygen and carbon dioxide concentrations (20.1% 02; 4.52% C02) of a standard gas sample were determined. In addition a calibrated sample of 99.5% 02 was used to check the upscale range of the oxygen analyzer. Test Procedures A sequence of four measurements of lung volume were taken. Prior to the first measurement, the subject was weighed, and the weight was recorded. The subject then sat in a chair, a nose clip was placed on his nose, and he inserted the mouth- piece of the rebreathing bag assembly into his mouth. The subject was instructed to exhale as forcefully as he could, and this procedure was repeated until it became apparent that the subject had truly made a maximal exhalation; the subject was then considered to be trained and ready to proceed with the determinations of lung volume. Residual Volume in Air After successfully performing a maximal exhalation as described above, the subject was instructed to again exhale maximally; upon reaching the point of maximal exhalation, he turned the three-way valve on the rebreathing bag assembly so 14 that he would inhale on the next breath from the rebreathing bag, which had been filled with two liters of 02. The subject then took three deep breaths. After the third exhalation, the subject turned the three-way valve back to its original posi- tion, and the gas in the bag was immediately analyzed for per- centage CO2 and 02' Residual Volume While Immersed to the Neck in Water Following the determination of residual volume in air, the rebreathing bag was flushed three times with O2 and refilled with two liters of 02. The rebreathing bag assembly was then attached by a clamp to a metal chair suspended above a swimming pool; the subject sat in the chair and put the mouthpiece of the rebreathing bag assembly in his mouth and the noseclip on his nose. The subject was lowered into the water by a hoist so that his shoulders were approximately one inch underwater. The same procedure was followed as in the pre- ceding determination; the subject exhaled maximally, turned the three-way valve, inhaled and exhaled three times from and into the rebreathing bag filled with 02, and turned the valve back after the third exhalation. The gas in the bag was analyzed for percentage CO2 and 02. Residual Volume While Fully Submerged in Water After the rebreathing bag was flushed, refilled with two liters of 02, and reattached to the metal chair, the chair and 15 subject were lowered into the water so that the subject's head was approximately one inch underwater. The subject was accli- mated to breathing underwater until he was able to stay under- water for fifteen seconds without undue stress. The subject was then resubmerged and made four respirations so that a baseline of four respiratory cycles was established on the recorder. The fourth exhalation was maximal and was held for five seconds. The subject turned the three-way valve. inhaled and exhaled three times, and turned the valve back. The gas in the bag was analyzed for percentage CO2 and 02, and the underwater weight at the point of the five-second maximal exhalation was noted. End-Tidal Volume While Fully Submerged in Water The rebreathing bag was again flushed and refilled with 02. The subject was resubmerged so that his head was approxi- mately an inch underwater, and he made four respirations to establish a baseline. The fourth exhalation was a normal one and was held for five seconds. The subject turned the three- way valve, inhaled and exhaled three times, and turned the valve back. The gas in the bag was analyzed for percentage CO2 and 02, and the underwater weight at the point of the five-second end-tidal exhalation was noted. Statistical Analysis Using residual volume while fully submerged, with the underwater weight recorded simultaneously, as the criterion 16 measure, t-tests for dependent samples were conducted com- paring other measures of residual volume and percent fat with those collected using the criterion measure. The significance level was set at p<.01. Pearson product-moment correlations were also calculated between the criterion measure of percent fat and other measures of percent fat. CHAPTER IV RESULTS AND DISCUSSION The purpose of this investigation was to study the effects of immersion in water upon residual volume and subsequent calculation of body density and to compare the effects of level of exhalation upon body density calculation. The data are presented in the following order: a. Predicted residual volume, residual volume measured in air, and residual volume measured with the subject immersed to the neck in water all in comparison with the criterion measure, i.e., residual volume measured with the subject fully immersed in water. Percent fat calculated using predicted residual volume, percent fat calculated using residual volume measured in air, percent fat calculated using residual volume measured with the subject immersed to the neck in water, and percent fat calculated using end-tidal volume all in comparison with percent fat calculated using the criterion measure of residual volume. Residual Volume The results for residual volume are presented in Tables 4.1 and 4.2. The differences between the criterion measure 17 l8 and other measures of residual volume were all statistically significant. Table 4.l.--Statistical Results, Descriptive, Residual Volume. End-Tidal RV Volume RV RV RV Fully Fully Predicted In Air Head Out Submerged Submerged i 1972 1426 1371 1205 1680 SD 256 360 327 443 525 Table 4.2.—-Statistical Results, Significance, Residual Volume. RV RV RV Predicted In Air Head Out RV Fully Submerged <.01 <.01 <.01 (Criterion Measure) Percent Fat The results for percent fat are presented in Tables 4.3, 4.4, and 4.5. The only measure of percent fat that was not significantly different from the criterion measure was that calculated from end-tidal volume. In addition, the measure of percent fat calculated from end-tidal volume was highly correlated with the criterion measure. 19 Table 4.3.--Statistical Results, Descriptive, Percent Fat. % Fat % Fat % Fat % Fat % Fat Fully End-Tidal Predicted In Air Head Out Submerged Volume X 9.08 12.51 12.68 13.70 13.81 SD 5.92 5.14 5.51 5.18 5.72 Table 4.4.--Statistical Results, Significance, Percent Fat. % Fat % Fat % Fat % Fat End-Tidal Predicted In Air Head Out Volume % Fat Fully Submerged <.01 <.01 <.01 .70 (Criterion Measure) Table 4.5.--Corre1ation, Percent Fat. % Fat End-Tidal % Fat % Fat % Fat Volume Predicted In Air Head Out % Fat Predicted .822 % Fat In Air .886 .883 % Fat Head Out .885 .904 .974 % Fat Fully Submerged .954 .853 .920 .922 (Criterion Measure) 20 Discussion It was the intention of this study to determine the effects of variations in methods of measuring lung volume upon the subsequent calculation of body density. The residual volumes of all subjects were measured under three conditions: in air, immersed to the neck, and fully submerged in water. These values, along with predicted residual volume and end- tidal volume were used in separate calculations of body den- sity. Statistical analyses were then made to determine whether or not there were significant differences between methods of measuring residual volume and whether or not these differences in lung volume resulted in significant differences in calculated body density. At this point it is important to review the hypotheses: Hypothesis 1: There is no difference between residual volume measurements made with subjects fully submerged in water (criterion measure) and those made under ordinary environmental conditions (in air) or while immersed to the neck. This hypothesis cannot be accepted. There were highly significant differences between the criterion measure of residual volume and those made in air or with the subject immersed to the neck (Table 4.2, p<.01). This finding is in the same direction as that of Brozek,.Henschel, and Keys (3), who found distinct, though not significant, decreases in residual volume when the subject was fully submerged. The present data tend to show that the further the body is immersed in water, the more the residual volume will decrease. 21 Hypothesis 2: Predicted residual volume, based upon subjects' height, weight, and age will not differ from residual volume measured with the subjects submerged in water. The data do not support this hypothesis. There is a highly significant statistical difference between the criterion measure of residual volume and predicted residual volume (Table 4.2, p<.01). Hypothesis 3: Body density calculation will not differ, regardless of whether lung volume is measured following maximal or end-tidal exhalation. The data collected in the present study support this hypothesis. No significant difference was found between body density at end-tidal exhalation and body density calculated using the criterion measure, i.e., residual volume while fully submerged (Table 4.4, p<.70). These data are at variance with that collected by Welch and Crisp (19), who found body density at full expiration to be lower than at one-half full expira- tion. The present data are, nevertheless, in agreement with those of Keys and Brozek (12) and Carlson and Chen (unpublished), who found that it made no difference what volume of air remained in the lungs at the moment the underwater weight was observed. CHAPTER V SUMMARY, CONCLUSIONS AND RECOMMENDATIONS Summary The purpose of this study was to determine the effects of immersion in water upon residual volume and subsequent body density calculation and to compare the effects of level of exhalation upon body density calculation. Thirty-five normal, healthy males, 18-28 years of age, served as subjects. A sequence of five measurements of lung volume were taken: residual volume in air, residual volume while immersed to the neck in water, predicted residual volume, residual volume while fully submerged in water, and end-tidal volume while fully submerged in water. In addition, the underwater weight of each subject was recorded simultaneously with the latter two measurements. Calculations of body den- sity were then made. The criterion measure, residual volume while fully submerged, was compared to the other measures of residual volume; similarly, the criterion procedure for measuring body density, based on residual volume measured with the subject fully submerged, was compared to the other pro- cedures for measuring body density.’ Data analysis was accom- plished by the use of dependent t-tests and correlation. 22 23 There were statistically significant differences between the criterion measure of residual volume and all other measures. Significant differences were also detected between the criterion measure of body density and all other measures of body density except one: there was no significant differ- ence between the criterion procedure for calculating body density and the procedure for calculating body density using end-tidal lung volume. Conclusions There was a significant difference between residual volume measured with the subject fully submerged and residual volume measured under ordinary environ- mental conditions or with the subject immersed to the neck. There was a significant difference between predicted residual volume and the criterion measure of residual volume. There was a significant difference between body den- sity measures based on the criterion measure of residual volume and those measures of body density based on other measures of residual volume. There was no statistically significant difference between the criterion measure of body density and the measure of body density based on end-tidal volume. With a correlation between these two measures of 24 .954, it is apparent that the determination of body density using end-tidal lung volume is a valid alternative to the criterion procedure. Recommendations Further studies should be made to test the reliability of the end-tidal procedure in comparison with the reliability of the criterion procedure for measure- ment of body density. In further studies of this nature, duplicate deter- minations should be made. 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