Exercise duration and thermoregulatory responses after whole body precooling.
Whole body precooling was hypothesized to reduce thermoregulatory and metabolic responses, thereby enhancing running time. Fourteen male runners completed two high-intensity running tests consisting of resting in 24 degrees C (normothermic condition; NC) or 5 degrees C (hypothermic condition; HC) for 30 min followed by 10-16 min of rest at 24 degrees C and then an exercise bout (24 degrees C) at 82% maximal aerobic capacity to exhaustion. Rectal temperature (Tre) before exercise was lower (by 0.37 degrees C; P < 0.005) and exercise duration was longer (by 121 +/- 24%; P < 0.05) in HC than in NC. Tre and mean skin (Tsk) and mean body (Tb) temperatures remained lower during HC (P < 0.01). Pre- and postexercise changes for Tsk, Tb, thermal gradient (Tre-Tsk), and heart rate (HR) were larger in HC than in NC (P < 0.05). Final Tre, Tre-Tsk, HR, and blood lactate were similar between HC and NC. During exercise, heat storage was greater (P < 0.01) in HC than in NC (173 +/- 46 and 143 +/- 38 W/m2, respectively) and subjects sweated more in NC than in HC (P < 0.01). O2 consumption was lower initially in HC than in NC (P < 0.05), but O2 pulse was not different. It was concluded that precooling results in greater exercise endurance with enhanced heat storage rate and less stress on metabolic and cardiovascular systems.
Lee
D T
DT
Department of Nutrition, Food, and Movement Sciences, Florida State University, Tallahassee 32306, USA.
Haymes
E M
EM
D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D001833:Body Temperature Regulation; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D013546:Sweating; D013997:Time Factors