Author and graduation date: Laura Jean PODEWILS, May, 1998

Committee members: Michael J. Buono (Chair), Mark Kern, Skaidrite Krisans

Thesis title: The Effect of Creatine Supplementation on Exercise Performance in the Heat

Creatine supplementation is associated with increases in body weight suggestive of an increase in fluid retention, yet this has not been fully established. The purpose of the current investigation was to look at body water changes and evaluate indicators of heat tolerance with creatine supplementation. Twenty college-aged males (mean age 22.15 + .80 years) were randomly assigned to a double blind protocol comparing creatine to a placebo over a 28-day period. Measurements of body weight, total body water, hydrostatically determined body composition, and hematocrit were taken across the time interval. Additionally, heart rate, core temperature, skin temperatures, hematocrit levels and sweat rate responses to an hour of exercise in the heat were assessed. No significant differences were found between groups at baseline. Body weight changes were significantly correlated to total body water changes, lending support to the original hypothesis that creatine increases fluid retention. With the exception of a single subject, results of a 2 x 2 ANOVA for repeated measures demonstrated a significant interaction of group by time, with the creatine group gaining weight and the placebo group staying relatively stable. Hydrostatically determined body fat percentage did not change significantly in either group; gains in weight were of the fat-free compartment. Further, a comparison of ending core temperatures from pre- to posttest procedures approached significance for the interaction (p = .052) with the creatine group temperatures declining and placebo temperatures closely resembling the pretest trial. A larger sample is necessitated to investigate whether a thermoregulatory advantage may exist with creatine supplementation. No significant differences were found for heart rate, skin temperature, sweat rate, or hematocrit levels in either group. Lack of changes in these measures, in consideration of creatine transport process as sodium dependent, supports intracellular water retention. These results suggest that the body weight gains with creatine supplementation may be explained by proportional total body water changes. More specific measurement techniques are warranted to determine specific changes in each of the body fluid compartments, as well as alterations in osmolarity with creatine supplementation.

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