The purpose of this study was to determine the reliability of within-day and between-day measurements of body volume (BV), thoracic gas volume (Vtg), and body fat percentages (%fat) taken in the BOD POD. Fifty subjects (25 men, 25 women) of varying ages (20-81 yrs.), races, and body composition (2.2-51.1% fat) were tested under ideal conditions set forth by the manufacturer at the same time of day (± 3 hours) on three separate days within two weeks. On each day, testing was repeated in succession until three trials were obtained which met the manufacturer's criteria for acceptable BV and Vtg. Repeated measures ANOVA revealed no significant mean differences between the three within-day trials or for the first trial between each of the three days with the exception of between-day BV where day 1 was found to be 260 ml greater than days 2 and 3. Coefficient of variation (SD/mean* 100) and intra-class correlations were determined for each variable both within the three trials of each day and between the first trials of each of the days. For BV, the CV for the 150 cases of within-day measurements was.1 ± .01% while the between-day CV was .4 +.3%. For both within and between day BV, r = .99. The CV and correlations for Vtg was 2.8 ± 2.4% and .99 and 4.1 ± 2.6% and .98 for within-day and between-day measures, respectively. The mean absolute difference between measured Vtg and the predicted value (Vpred) from age, height, and weight was 0.471 ± 0.392 L which would result in body fat estimates that differ by 1.3 ± 0.3%. Estimates of body fat from Vpred were within +2% fat of those derived from measured Vtg values in 80% of the trials. Body fat percentage produced a within-day CV of 2.8 + 4.6% with an r = .99 and a between-day CV of 3.8 ± 5.9% with an r =.99. However, with the exclusion of 3 subjects with body fat <7%, the within-day and between-day CV decreased to 2.0 ± 1.8% and 2.7 ± 2.1%, respectively. The difference between the first two trials of each day was < 2% fat in 93% of the cases, and all 150 cases resulted in fat within + 2% in the three trials. In conclusion, these results support that BOD POD measurements of BV, Vtg, and % fat are reliable both within and between days for a wide range of adults. Also, to obtain the most reliable measurement of % fat in the BP, measuring thoracic gas volume and averaging the values obtained from two trials which agree within + 2 % fat is recommended. / School of Physical Education

The BOD POD (BP) is a device used for determining body composition that is based on the air displacement plethysmography method. There has been little research conducted on the BP, and the main focus of the research has been on the reliability and validity of the BP. Another important area of research with the BP is the effect that different types of clothing have on the percent fat readings from the BP. To produce the most accurate results, the manufacturers recommend that subjects wear a Lycra swimsuit, however this recommendation may not be feasible for some individuals or testing sites to follow. The purpose of this study was to determine if a standard type of clothing would affect the percent fat readings from the BP in a consistent manner. Fifty subjects (25 men, 25 women) of varying ages (19 to 84 years of age) and body composition (3.4 to 53.2% fat) completed six trials (3 cotton and 3 nylon) in the BP during one testing session. With the exception of the clothing, all other recommendations by the manufacturer were followed. The comparison between the two clothing conditions was analyzed with a 2-way ANOVA (gender x clothing), frequency distribution, and the Bland-Altman method. The reliability of the measurements was analyzed by comparing the absolute differences between the three trials with cotton clothing and the three trials with nylon clothing, with intra-class correlation coefficients, and the Bland-Altman method. The results from the 2-way ANOVA revealed that the interaction effect of gender and amount of clothing was significant with the difference between nylon versus cotton being 1.1% for men and 4.8% for women. There was also a significant difference between body fat measurements with the cotton clothing (24.2 + 11.2%) and the nylon clothing (27.1 + 11.6%) when analyzed with all the subjects combined (men and women). Reliability analysis resulted in intra-class correlation coefficients of 0.9 and 0.95 within the cotton and nylon clothing trials, respectively. The comparison of the absolute differences between the cotton trials and the nylon trials showed a between-trial standard deviation of approximately 0.6 for cotton and 0.7 for nylon. In the comparison of nylon to cotton clothing results, there was a greater difference between the results for the women than for the men. The men had a lower, similar difference when comparing the two clothing conditions, whereas the women had a higher, difference that was not similar between subjects. In conclusion, this study showed that using either cotton or nylon shorts for men is acceptable, whereas for women more testing is needed to find another type of clothing to replace the Lycra swimsuit that results in consistent percent fat measurements. Also, the reliability of the percent fat readings obtained with both clothing conditions was very good. / School of Physical Education

The purpose of this study was to examine the effects of hydration on %BFADP while using %BFDEXA as the criterion measure. Twenty healthy males and females ages 20-28 participated in the study. The subjects underwent dehydration in the environmental chamber at 32°C and 50% relative humidity until a total of 3% of their body weight had been lost. Subjects were measured with ADP and DEXA at euhydration, 1%, 2%, and 3% dehydration. The results revealed significant differences between %BFADP and %BFDEXA at each level of hydration. %BFDEXA did not change due to dehydration; however, %BFADP decreased as a result of dehydration. Therefore, standardization criteria must be employed in order to assure proper hydration and accurate %BF measurements via ADP. / School of Physical Education

No research has been performed comparing percent body fat measurements using dual energy x-ray absorptiometry (DEXA) and air plethysmography after weight loss. The purpose of this investigation was to compare body composition assessments using the Bod Pod® Body Composition System (BP) and the DEXA ProdigyTM before and after an 8-week weight loss diet and exercise program. Based on prior comparison studies, it was hypothesized that percent fat values would be significantly lower using the BP compared to the DEXA before and after weight loss. Also since both methods have been shown to be reliable, it was hypothesized that the BP and DEXA would detect similar changes in percent fat in response to a weight-loss intervention. Twelve women (42 ± 8 yrs) and ten men (40 + 11 yrs) had their percent body fat estimated using the BP and whole body DEXA ProdigyTM scanner. A similar significant (P < 0.05) decrease in percent body fat was observed using the BP and DEXA ProdigyTM (-2.2% and -1.8%, respectively) after weight loss. Percent body fat using the BP was significantly lower than the DEXA ProdigyTM before (36 ± 10.7% and 38.1 ± 9.4%, respectively) and after (33.8 ± 10.8% and 36.3 + 10.6%, respectively) the weight loss program. Significant Pearson correlation coefficients between the DEXA ProdigyTM and the BP were noted pre (r = 0.975) and post (r = 0.968) weight loss. These data indicate the BP provides significantly lower absolute %fat values within a range of body fat levels (20-56%) when compared to the DEXA. However, the BP and DEXA detect similar changes in %fat, fatfree mass, and fat mass from weight loss in men and women. Also, the BP consistently overestimated fat-free mass and underestimated %fat and fat mass compared to values obtained from DEXA. / School of Physical Education

The prevalence of obesity has made it necessary to develop a convenient, reliable and safe tool for timely assessing and monitoring this condition in public health. We suggest that three-dimensional (3D) anthropometry can provide a convenient, accommodating and comprehensive means to body composition assessment. A 3D anthropometry system based on stereo vision technology is developed. To make it more portable and affordable, the system is reduced to a two-stance design and only uses off-the-shelf components. The system is calibrated in two separate stages: camera calibration and 3D registration. The first stage is relatively complicated, but there is no need to repeat frequently. Therefore, only 3D registration is required when the system is transported. This property contributes to the portability and also reduces cost of maintenance. In this system, image acquisition can be completed in 200 ms, which is important in reducing artifacts caused by slight body movement. However, the computation in stereo vision is complex and intensive, and is still a challenge. A two-phase stereo matching algorithm is developed. In the first phase, the foreground is accurately segmented with the help of a predefined virtual interface, and a coarse disparity map is generated with block matching. In the second phase, local least squares matching is performed in combination with global optimization within a regularization framework, so as to ensure both accuracy and reliability. To make the 3D data more interpretable and manageable, it is essential to convert the raw 3D data to a surface model. For our system, a unique challenge is that there are large gaps in the data caused by occlusions. An effective surface reconstruction algorithm based on subdivision surface representation is developed. It has been verified that the algorithm is reliable in gap closing, accurate in representation, and efficient in data compression. To make the 3D anthropometry system ready for practical use, a body measurement system dedicated to body composition assessment is developed based on an earlier system that was designed for applications in apparel fitting. The functions of 3D measurement are enhanced by taking advantage of modern graphics hardware. The overall performance of the presented system has been evaluated on mannequins and human subjects. It has been shown that the measurements are highly repeatable. The feasibility of 3D anthropometry in body fat assessment has been demonstrated in comparison to air displacement plethysmography and bioimpedance analysis. / text

Whole-body bioelectrical impedance analysis (BIA) was evaluated for its reliability and accuracy in estimating body composition in children and youth. The established electrical principle for estimating volume in a geometrical system from conductor-length('2) divided by impedance is the basis for the use of this method in humans. The hypothesis that body-height('2) divided by the resistance component of impedance (resistance index) can be used to estimate total body water (TBW), fat free body (FFB), and percent fat (%FAT) was tested. Validation studies in adults indicate BIA is a reliable and fairly accurate method of estimating TBW, FFB, and %FAT but no testing has been completed on children. The subjects were 103 nonobese and obese anglo males and females from 10 to 14 years old. Within-day reliability of resistance and reactance was assessed by analysis of variance with built-in comparisons. Between-day reliability for all measurements, made four to five weeks apart, was evaluated by test-retest correlation coefficients and paired t-tests. The criterion variables were FFB and %FAT estimated using equations developed for children and youth based on: (1) skinfolds, (2) body density, (3) TBW, (4) density and TBW, (5) density, TBW, and bone mineral content. Regression and multiple regression analyses were used to select the most accurate method of measuring FFB and %FAT and to determine the relationship among criterion variables and the following independent variables: resistance index alone and combined with sex, fatness category, sex x fatness, age, sexual maturation status, weight, anthropometric variables, and reactance. From this study the following conclusions were made: (1) BIA measurements were reliable, (2) resistance index had a linear relationship with FFB estimated from several criterion variables, (3) weight, sex, fatness category, sex x fatness, age, and sexual maturation status were significant variables for predicting criterion variables used in combination with resistance index but were not significant when anthropometric variables were included in the analysis, (4) prediction accuracy for FFB and %FAT from resistance index was fair (SEE 2.58 kg and 4.21%) and from resistance index plus anthropometric variables and reactance was good (SEE 1.88 kg and 3.26%) and similar to that from the best anthropometric variables alone (SEE 2.11 kg and 3.19%).

The purpose of this study was to examine the effects of hydration status on the prediction of body composition using BIA, NIR, and DEXA. Twenty healthy males and females ages 18 to 28 were recruited for this study. The subjects were dehydrated in the climate control chamber and engaged in physical exercise, until they lost approximately 1%, 2%, and 3% of their pre-exercise body weight. Percent body fat (%BF), body weight, and urinalysis measures were taken initially on day 1, on day 4 at euhydration, following 1%, 2%, and 3% dehydration, and upon rehydration during day 5. The results indicated that there were significant decreases for %BFBIA and %BFNIR between euhydration and 1%, 2%, and 3% dehydration. %BFDExA did not significantly change.There were also significant differences in the response to dehydration between each technique. Proper hydration should be ensured before %BF is estimated with BIA and NIR. / School of Physical Education

Health care professionals require accurate measurements of body composition and the hydrostatic weighing method is widely used as a reliable technique. Hydrostatic weighing measures body density accounting for an individuals residual volume (RV). To determine differences of RV measured in air (RVA) and in water (RVW), college-age men and women (n=51) were randomly assigned to one of four groups: female RVA, female RVW, male RVA, or male RVW. To account for possible gender differences with protocol (RVA vs. RVW) male and female subjects were treated as separate groups. RVW subjects began the first two trials in water followed by two trials out of water. If RV measures differed by more than 200 ml between the first two trials either in water or in air, a third or fourth trial was completed until two RV measures were within 200 ml of each other. The two trials were then averaged to determine the RVW. The same procedure was used for RVA subjects. RV was determined by the closed circuit helium dilution method. A 2-factor repeated measures ANOVA revealed that there was no statistically significant interaction between genders and protocols, a statistically significant difference between genders, and a statistically significant difference between protocols (RVA vs. RVW). The RV mean decreased with immersion in water among college-age subjects. A decrease in RV will have a marked increase in estimation of percent body fat. Therefore, the results of this study indicate that measuring RV during immersion in water on college-age men and women, to accurately assess body composition, is a valid and recommended protocol.

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The purpose of the present study was to investigate if any relationship exists between anthropometric measurements with average concentric velocity (ACV) at various intensities in the back squat and the number of repetitions able to be performed during a set to volitional fatigue at 70% of one-repetition maximum (1RM). It was hypothesised that short femurs and total height would be related to slower ACVs and lower total number of repetitions performed. 58 resistance trained subjects were recruited and attended one day of data collection. Subjects performed 1RM testing of the back squat followed by two single repetition sets at 30-90% of 1RM and a 70% of 1RM set to fatigue. There was no significant correlation between femur length and height with ACV at any intensity (p>0.05). A significant negative correlation existed between both height (r=-0.39, p=0.003) and femur length (r=-0.31, p=0.018) with total number of repetitions performed. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection