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