Thesis (M.S.)--University of Michigan, 1995. / Thesis date on spine.

Thesis (M.S.)--University of Michigan, 1995. / Thesis date on spine.

Background: Childhood overweight and obesity remains high, contributing to cardiometabolic risk factors at younger ages. It is unclear which measures of adiposity serve as the best proxies for identifying children at metabolic risk. This study assessed whether DXA-derived direct measures of adiposity are more strongly related to cardiometabolic risk factors in children than indirect measures. Methods: Anthropometric and DXA measures of adiposity and a comprehensive assessment of cardiometabolic risk factors were obtained in 288, 9-12 year old girls, most being of Hispanic ethnicity. Multiple regression models for each metabolic parameter were run against each adiposity measure while controlling for maturation and ethnicity. In addition, regression models including both indirect and direct measures were developed to assess whether using direct measures of adiposity could provide a better prediction of the cardiometabolic risk factors beyond that of using indirect measures alone. Results: Measures of adiposity were significantly correlated with cardiometabolic risk factors (p < 0.05) except fasting glucose. After adjusting for maturation and ethnicity, indirect measures of adiposity accounted for 29-34% in HOMA-IR, 10-13% in TG, 14-17% in HDL-C, and 5-8% in LDL-C while direct measures accounted for 29-34% in HOMA-IR, 10-12% in TG, 13-16% in HDL-C, and 5-6% in LDL-C. The addition of direct measures of adiposity to indirect measures added significantly to the variance explained for HOMA-IR (p = 0.04). Conclusion: Anthropometric measures may perform as well as the more precise direct DXA-derived measures of adiposity for assessing most CVD risk factors in preadolescent girls. The use of DXA-derived adiposity measures together with indirect measures may be advantageous for predicting insulin resistance risk.

The purpose of the study was to examine the relationship and comparisons of athletic amenorrhea and bone mineral density in adolescent, cross-country runners. Subjects: Twenty-eight female adolescent cross-country runners (Mean Age + SD = 15.0 + 1.3 years); consisting of seventeen eumenorrheics & eleven amenorrheics. Design: The design consisted of a sixmonth longitudinal design in which the subjects were measured before and after cross-country season for height, weight, and lean tissue (LT), body fat (BF), bone mineral content (BMC), and bone mineral density (BMD) using whole-body scan densitiometry with a Lunar Dual-energy X-ray Absorptiometer (DXA). Run performance, weekly training volumes, menstrual dysfunction, menarchal age, nutritional information, and stress fractures were reported by the subjects. Statistical analyses consisted of Pearson product-moment and partial correlations to examine the associations of the variables, paired t-tests to measure seasonal body composition changes, multivariate analysis (MANOVA & MANCOVA) to investigate the subgroup differences of variables, and simple linear regression to determine the best body composition predictor variable for BMD. Results: The eumenorrheic subgroup's BMD was significantly greater than the amenorrheic subgroup's BMD (F(1, 54) = 16.22, p<.05, partial h² =.231). The eumenorrheic subgroup's bodyweight (F(1, 54) = 7.65, p<.05, partial h² =.124), BF (F(1, 54) = 8.56, p<.05, partial h² =.137), and BMC (F(1, 54) = 8.52, p<.05, partial h² =.136) were significantly greater than the amenorrheic subgroup. There was also a significant seasonal increase in BMD (t(27) = -4.01, p <.05) for the overall group. Bodyweight was the body composition component that best predicted BMD (F(1, 26) = 46.434, p<.05, R² =.641). There were no significant subgroup differences with respect to run performance, stress fractures, and nutritional supplementation. Conclusions: Athletic amenorrhea was highly associated with lower levels of BMD in adolescent, cross-country runners. Athletic amenorrhea was also highly associated with lower levels of bodyweight, BF, and BMC in adolescent cross-country runners. Finally, cross-country running was highly associated with increased BMD in adolescent athletes. Implications: The long-term implication of the study is that subjects with lower levels of BMD may be at a greater risk of osteoporosis. Recommendations: Educate and instruct runners to utilize proper training methods so the healthful benefits of crosscountry running, as well as improved performance, are obtained.

No description available.

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

Purpose: This is the first study done to determine the efficacy of 10-weeks of Nexersys training on improving cardiovascular fitness (CF) and body composition (BC). Nexersys is an "exergaming" system that combines mixed martial arts, high-intensity interval training and core work into an interactive unit with a monitor and 7-strike pads. Participants were provided a Nexersys unit in their homes to complete 10-weeks of training 3 to 4 times a week progressing from 5, 3-min rounds with a minute rest to 15 rounds at the end of 10-weeks. Participants were tested on 3 separate occasions, prior to beginning training (0wk), at 5-weeks (5wk) and 10-weeks (10wk). Body mass (BM), percent body fat (%BF), fat mass (FM) and lean mass (LM) were assessed using dual-energy X-ray absorptiometry (DEXA). CF was assessed during a 10-round Nexersys bout (NB) and a VO2max treadmill (VO2max) test. CF during NB and VO2max treadmill test was assessed by using regression analysis to determine the estimated average heart rate for a range of VO2 10-25 ml/kg/min (HRN) and 10-30 ml/kg/min (HRV) respectively. Results and Conclusion: Relative to starting values, BM did not change (79.8 ± 7.9 to 79.7 ± 7.5 kg). %BF and FM decreased from starting values (36.0 ± 3.4% to 34.1 ± 5.3%, p=0.003 and 30.0 ± 4.9 kg to 28.4 ± 4.6 kg, p=0.045, respectively). LM increased from starting values (46.7 ± 3.5kg to 48.4 ± 3.6kg, p=0.001). HRN and HRV decreased from starting (148 ± 2.7 to 140.8 ± 1.9 bpm, p=0.003 and 148 ± 1.8 to 140.1 ± 1.8 bpm, p=0.003, respectively). VO2max trended to increase but did not reach statistical significance (33.9 ± 1.7 to 36.3 ± 1.7 ml/kg/min, p=0.054). These findings suggest 10-weeks of Nexersys training improves body composition both by increasing LM and decreasing BF with no change in BM. CF improved at submaximal intensities. / text

No description available.

Blood pressure (BP) measurement reliability, year-to-year BP tracking, distinguishing characteristics of upper quintile (UQ) vs lower four quintiles' (LQ) systolic BP (SBP) tracking and the relationships of fat distribution and body composition to SBP were examined in 57 youth. Subjects were measured on two occasions approximately one year apart. Longitudinal measures included auscultatory BPs, height, weight, body circumferences, skeletal widths, bioelectrical impedance and skinfolds. Inter-trial reliability of right/left arm averaged BP (RLBP) exceeded that of either limb alone; tracking magnitude was likewise greater with RLBP. Greater total body mass and fatness as well as larger anthropometric dimensions distinguished UQ from LQ SBP trackers. Fat distribution and SBP were not consistently associated with each other across study years. Irrespective of gender differences, fatness and fat free mass per unit height2 were independently related to within year SBP, yet only initial fatness was independently predictive of future SBP.

No description available.