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The purpose of this investgation was to study the effects of repeated weight loss and physical training on the plasma levels of testosterone, growth hormone, insulin and cortisol. A further purpose of this study was to determine if changes in plasma hormone concentrations could be avoided through a nutritional education program and the addition of nutritional supplements to the diet. Lastly the effects of acute and seasonal weight loss upon mean anerobic power, peak power, and percent fatigue were measured.MethodsA total of 34 adolescent high school wrestlers ranging age from 14 to 18 years, were pair matched for age, size, percentage weight loss, and skill level (varsity or JV) and then randomly assigned into a control and treatment group. The treatment group recieved a nutritonal education program and nutritional supplements. Blood samples were taken four times throughout the study period: once in the preseason (October 14), twice in December (Dec. 7 and 14), and once in January (Jan. 13). The blood was drawn at the same time each morning after an 8 hour fast. The blood was analyzed to detect changes over time and between groups for hemoglobin, hematocrit, and plasma levels of insulin, cortisol, testosterone, and growth hormone. The wrestlers were also measured for caloric and nutrient intake, weight, height, body fat percentages, and for arm power with the Wingate test. The experimental design consisted of a pretest-posttest randomized groups test design. The hormone and power data were analyzed with a repeated measures ANOVA, and a probability level of 0.05 or above was chosen as statistical significance. Polynomial contrasts were used to determine whether significant differences over time followed linear, quadratic, or cubic trends. Post hoc tests were also used to determine where the difference did exist.ResultsThere were no significant (p<0.05) differences between the treatment and control groups in any variable tested. Over the experimental period, each group showed significant (p<0.05) decreases in weight, percent body fat, and fat free weight. No significant changes (p<0.05) in any of the power indicies occurred, but specific trends were apparent. Both groups had reductions in their absolute peak and mean power, and increases in their relative peak and mean power. Changes in percent fatigue and fatigue slope were inconsistent and nonsignificant. Serum concentrations of cortisol and insulin showed significant (p<0.05) decrements over the investigative period. The decline in serum growth hormone levels approached significance (p = 0.085), and serum testosterone levels showed a nonsignificant decreasing trend. Hormone levels per kilogram free fat weight were not changed, along with testosterone to cortisol ratios, hemoglobin and hematocrit levels.ConclusionsThe treatment of consuming a nutritional beverage (Exceed) and information on proper dieting did not produce a significant (p<0.05) difference between the groups. Over time the wrestlers lost significant amounts of weight, body fat, and fat free weight due to significant decreases in the intake of calories in the form of fat, protein and carbohydrate. There were also significant decreases in plasma levels of insulin and cortisol. These results indicate that weight loss over a wrestling season may significantly alter plasma hormone levels. / School of Physical Education

Twelve highly trained collegiate wrestlers were studied to determine if performance of a six-minute arm crank task can be maintained by feeding a hypocaloric, high percentage carbohydrate diet to athletes during a four day weight loss period. Subjects were placed on a hypocaloric, low percentage (41.9%) carbohydrate diet (LC) and a hypocaloric, high percentage (65.9%) carbohydrate diet (HC) during two separate weight loss periods. The reduction in work performed during six minutes of arm cranking from pre- to post-weight loss was 0.9% and 8.2% for HC and LC treatments, respectively. Post exercise lactate measures were significantly lower and pH values were significantly higher pre- and post-weight loss under the LC treatment as compared to the HC treatment. Pre-exercise glycerol values were significantly higher post weight loss as compared to pre weight loss under both diet treatments. Profile of Mood State (POMS) scores indicate a negative effect of weight loss on psychological well being of the subjects. This negative effect is exacerbated during weight loss under the LC as compared to HC treatment. These data indicate a significant reduction in performance following a four day weight loss of 6.1% under the LC treatment, while performance is maintained following the HC treatment. / Department of Biology

The purpose of this investigation was to examine the seasonal change in the nutritional protein status of adolescent wrestlers who lost weight for competition. Additionally, this study determined if changes in plasma proteins and amino acids could be prevented through nutritional education and dietary supplementation. Twenty-seven adolescent wrestlers (14.8-18.1 yr) were divided into two groups for study during a three month period. One group received a nutritional education and supplement program, the other group served as a control. Height, weight, percent body fat, and free fat weight were measured during wrestling season. Venous blood samples were drawn and analyzed for essential (E) and nonessential (NE) plasma amino acids, hemoglobin (Hb), hematocrit (Hct), retinol-binding protein (RBP), prealbumin (PA), albumin (AL), and blood urea nitrogen (BUN). Four, 4-day dietary records taken during the season were analyzed for protein, carbohydrate, fat, and total calories. The results demonstrated that weight, percent body fat, and fat free weight decreased significantly during the experimental period (p<0.001), with no significant differences between treatment and control groups. The blood RBP and PA decreased significantly during the experimental period (p<0.01), whereas AL didNot change. Most of the amino acids did not show significant decreases during the experimental period whereas the total essential amino acids showed a decreasing trend (p<0.05), the total nonessential amino acids did not change. The subjects' average caloric intake showed significant decreases during the experimental period (p<0.001). The wrestlers failed to meet the RDA for energy and protein intake. It was concluded that nutritional status of adolescent wrestlers appears to be diminished as a result of weight loss during the season. / Human Performance Laboratory

published_or_final_version / abstract / toc / Zoology / Doctoral / Doctor of Philosophy

The purpose of this thesis was to monitor body composition and energy expenditure changes during weight loss in subjects encouraged to maintain a diet equal to 90% of resting energy expenditure (REE). Over six months, 69 female subjects had REE measured at baseline and weeks 13 and 25 with fortnightly body composition measurements. Subjects lost significant total body mass (17.2 lb) and fat mass (16.7 lb) (p≤.000). Fat-free mass remained stable during the six month period. REE was significantly higher at baseline (1701.1 kcal) than weeks 13 (1576.3 kcal) and 25 (1579.4) (p≤.000); REE at weeks 13 and 25 were similar (p≥.05). Predicted REE at weeks 13 (1671.3 ± 254.7 kcal) and 25 (1658.5 ± 252.4 kcal), compared to measured REE, was significantly lower, 1576.3 kcal and 1579.4 kcal, respectively (p≤.000). Results of this study illustrate that individuals can lose significant amounts of total body mass while preserving fat-free mass and that during active weight loss, there is a metabolic adaptation to reduced caloric intake. / Department of Family and Consumer Sciences

Please read the abstract in the section 00front of this document / Dissertation (MA (HMS))--University of Pretoria, 2007. / Biokinetics, Sport and Leisure Sciences / unrestricted