The influence of whole-body vs. torso pre-cooling on physiological strain and performance of high-intensity exercise in the heat

Little research has been reported examining the effects of pre-cooling on h igh-intensity exercise performance, particularly when combined with strateg ies to keep the working muscle warm. This study used nine active males to d etermine the effects of pre-cooling the torso and thighs (LC), pre-cooling the torso lice-vest in 3 degreesC air) while keeping the thighs warm (LW), or no cooling (CON: 31 degreesC air), on physiological strain and high-inte nsity (45-s) exercise performance (33 degreesC, 60% rh). Furthermore, we so ught to determine whether performance after pre-cooling was influenced by a short exercise warm-up. The 45-s test was performed at different (P < 0.05 ) mean core temperature [(rectal + oesophageal)/2] [CON: 37.3 +/- 0.3 (S.D. ), LW: 37.1 +/- 0.3, LC: 36.5 +/- 0.4<degrees>C] and mean skin temperature (CON: 34.6 +/- 0.0, LW: 29.0 +/- 1.0, LC: 27.2 +/- 1.2 degreesC) between al l conditions. Forearm blood flow prior to exercise was also lower in LC (3. 1 +/- 2.0 ml 100 mi tissue(-1) min(-1)) than CON (8.2 +/- 2.5, P = 0.01) bu t not LW (4.3 +/- 2.6, P = 0.46). After an exercise warm-up, muscle tempera ture (T-m) was not significantly different between conditions (CON: 37.3 +/ - 1.5, LW: 37.3 +/- 1.2, LC: 36.6 +/- 0.7 degreesC, P = 0.16) but. when war m-up was excluded, T-m was lower in LC (34.5 +/- 1.9 degreesC, P = 0.02) th an in CON (37.3 +/- 1.0) and LW (37.1 +/- 0.9) Even when a warm-up was perf ormed, torso + thigh pre-cooling decreased both peak (-3.4+/-3.8%, P = 0.04 ) and mean power output (-4.1 +/- 3.8%, P = 0.01) relative to the control, but this effect was markedly larger when warm-up was excluded (peak power - 7.7 +/- 2.5%, P = 0.01; mean power -7.6 +/- 1.2%, P = 0.01). Torso-only pre -cooling did not reduce peak or mean power, either with or without warm-up. These data indicate that pre-cooling does not improve 45-s high-intensity exercise performance, and can impair performance if the working muscles are cooled. A short exercise warm-up largely removes any detrimental effects o f a cold muscle on performance by increasing T-m. (C) 2001 Elsevier Science Inc. All rights reserved.