A Comparison of Thermoregulation With Creatine Supplementation Between the Sexes in a Thermoneutral Environment

OBJECTIVE: To compare the effect of creatine supplementation on thermoregulation in males and females during exercise in a thermoneutral environment. DESIGN AND SETTING: Male and female subjects participated in 30 minutes of cycle ergometry in nonsupplemented (NS) and creatine-supplemented (Cr) conditions at 70% to 75% of predetermined peak oxygen consumption. SUBJECTS: Ten male and ten female subjects were evaluated with and without creatine supplementation. MEASUREMENTS: Analyses were performed during exercise for core temperature and mean skin temperature using two 2 x 2 x 7 mixed-factorial analyses of variance (ANOVAs). We compared mean differences between NS and Cr conditions and sex for heart rate, systolic blood pressure, and diastolic blood pressure using 3 2 x 2 x 4 mixed-factorial ANOVAs. Three 2 x 2 mixed-factorial ANOVAs were computed to examine differences between sex and conditions for the following variables: nude body weight and blood urea nitrogen before and after exercise and urine specific gravity. RESULTS: Significant time effects were found for core temperature, skin temperature, heart rate, and diastolic blood pressure. Time effect and difference between the sexes for systolic blood pressure were both significant. Differences in nude body weight and blood urea nitrogen before and after exercise were greater for males, but there was no difference between conditions. No significant difference between sex and condition for urine specific gravity was noted. CONCLUSIONS: Short-term creatine supplementation did not affect thermoregulation between the sexes when exercising in a thermoneutral environment. Differences in changes in nude body weight before and after exercise may be due to a higher sweating rate in males versus females. Differences in blood urea nitrogen before and after exercise between the sexes may be due to a reduced glomerular filtration rate coupled with greater muscle creatine breakdown in males.