Effects of creatine on thermoregulatory responses while exercising in the heat.
OBJECTIVE
We hypothesized that creatine supplementation would interfere with normal body fluid shifts that occur during exercise in a hot environment due to its osmotic effect intracellularly. This study examined the effects of acute creatine loading (20 g/d for 5 d) on the thermoregulatory response of the body during a bout of exercise at 39 degrees C.


METHODS
Subjects (15 men and 1 woman) performed a cycle test of maximum oxygen consumption to determine the proper work rate for the heat-stress test (40 min at 55% maximum oxygen consumption at 39 degrees C) and were assigned to a creatine group (n = 8) or a placebo group (n = 8) in a double-blind fashion. Each group performed the heat-stress test on two separate occasions: before supplementation and after supplementation (20 g/d of creatine with Gatorade or Solka-floc plus Gatorade). Dependent variables included rectal temperature, mean skin temperature, mean body temperature, and perceived thermal sensation.


RESULTS
Repeated measure analysis of variance showed a significant (P < or = 0.05) increase in body weight in the group supplemented with Gatorade. Core temperature was significantly lower after supplementation for both groups combined (before supplementation at 37.85 degrees C and after supplementation at 37.7 degrees C), with no difference between groups. A significant three-way interaction (group x trial x time) was also found for rectal temperature, with both groups having significantly lower rectal temperature after supplementation. Mean body and mean skin temperatures showed no differences.


CONCLUSIONS
Short-term creatine supplementation (20 g/d for 5 d) did not have a negative effect on thermoregulatory responses during exercise at 39 degrees C.
Mendel
Ronald W
RW
Ohio Research Group, Wadsworth, Ohio, USA. rwmendel@wadsnet.com
Blegen
Mark
M
Cheatham
Chris
C
Antonio
Jose
J
Ziegenfuss
Tim
T
D000328:Adult; D000704:Analysis of Variance; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects* / Q000502:physiology; D001835:Body Weight / Q000187:drug effects; D003401:Creatine / Q000494:pharmacology*; D019587:Dietary Supplements; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D012881:Skin Temperature / Q000187:drug effects; D013997:Time Factors
D003401:Creatine