The Effects Of Creatine Supplementation On Thermoregulation And Isokinetic Muscular Performance Following Acute (3-day) Supplementation

Abstract

PURPOSE: The purpose of this investigation was to determine the effects of 3-d of creatine supplementation on thermoregulation and muscle force output. METHODS: 14 males participated in two exercise bouts (thermoregulation and muscle force), following 3-d of creatine supplementation (0.3 g/kg total body weight) or placebo. For the thermoregulation session subjects ran for 60 min at 60-65% of VO2max in the heat (32.58 + 0.91°C; 18.52 + 4.79%). Immediately following the thermoregulation session muscular force output was measured isokinetically at velocities of 60, 180, and 300°/s. Pre- and post-test thermoregulatory measures included nude body weight (NBW), urine specific gravity (USG), total body water (TBW), extracellular water (ECW), intracellular water (ICW), serum creatine levels (SCR), and urinary creatinine levels (UCR). During the 60 min run core temperature (Tr) was assessed in 5 min intervals. Peak torque was used to assess isokinetic muscular force output. The velocities and repetitions included 60°/s × 10 reps; 180°/s × 15 reps; and 300°/s × 30 reps. RESULTS: Tr increased over the 60 min run for both conditions. For TBW and ECW there were significant (p <.05) treatment and time effects. TBW was significantly greater following creatine supplementation versus placebo, and pre-test TBW values were greater than post-test TBW values. ECW was greater following creatine supplementation versus placebo, and pre-test ECW values were significantly less than post-test ECW values. No significant difference (p >.05) was found between conditions for ICW, NBW, USG, UCR, and SCR. However, pre-test scores for ICW, USG, UCR, and SCR were significantly less (p <.05) at pre-test versus post-test. There were no significant differences (p >.05) in peak torque values between conditions for each velocity. A significant (p <.05) overall velocity effect was found for both flexion and extension. As velocity increased, mean peak torque values decreased. CONCLUSIONS. 3-d of creatine supplementation does not effect thermoregulation during submaximal exercise in the heat. The lack of difference in peak torque values suggests that 3-d of creatine supplementation is not enough to elicit an ergogenic effect for muscle force output following endurance activity.