Dt. Lee et Em. Haymes, EXERCISE DURATION AND THERMOREGULATORY RESPONSES AFTER WHOLE-BODY PRECOOLING, Journal of applied physiology, 79(6), 1995, pp. 1971-1976
Whole body precooling was hypothesized to reduce thermoregulatory and
metabolic responses, thereby enhancing running time. Fourteen male run
ners completed two high-intensity running tests consisting of resting
in 24 degrees C (normothermic condition; NC) or 5 degrees C (hypotherm
ic condition; HC) for 30 min followed by 10-16 min of rest at 24 degre
es C and then an exercise bout (24 degrees C) at 82% maximal aeorbic c
apacity to exhaustion. Rectal temperature (T-re)before exercise was lo
wer (by 0.37 degrees C; P < 0.005) and exercise duration was longer (b
y 121 +/- 24%; P < 0.05) in HC than in NC. T-re and mean skin ((T) ove
r bar(sk)) and mean body ((T) over bar(b)) temperatures remained lower
during HC (P < 0.01). Pre- and postexercise changes for (T) over bar(
sk), (T) over bar(b), thermal gradient (T-re - (T) over bar(sk)), and
heart rate (HR) were larger in HC than in NC (P < 0.05). Final T-re, T
-re - (T) over bar(sk), HR, and blood lactate were similar between HC
and NC. During exercise, heat storage was greater (P < 0.01) in HC tha
n in NC (173 +/- 46 and 143 +/- 38 W/m(2), respectively) and subjects
sweated more in NC than in HC (P < 0.01). O-2 consumption was lower in
itially in HC than in NC (P < 0.05), but O-2 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 card
iovascular systems.