Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat

Body cooling before exercise (i.e. pre-cooling) reduces physiological strai n in humans during endurance exercise in temperate and warm environments, u sually improving performance. This study examined the effectiveness of pre- cooling humans by ice-vest and cold (3 degreesC) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performa nce in the heat (35 degreesC, 60% RH). Nine habitually-active males complet ed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degreesC air) before 35-min cycle exercise: 20 min at similar to 65% (V) over dot O-2peak then a 15-min work-performance trial. At exercise onset, mean core ((T) over bar (c), from oesophagus and rectum) and skin temperatu res, forearm blood How (FBF), heart rate (HR), and ratings of exertion, bod y temperature and thermal discomfort were lower in LW and LC than CON (P < 0.05). They remained lower at 20 min [e.g. <(T)over bar>(c): CON 35.4 +/- 0 .2 (+/- S.E.), LW 37.9 +/- 0.1, and LC 37.8 +/- 0.1 degreesC; HR: 177 +/- 3 , 163 +/- 3 and 167 +/- 3 b.p.m), except that FBF was equivalent (P = 0.10) between CON (15.5 +/- 1.6) and LW (13.6 +/- 1.0 ml 100 mi tissue(-1). min( -1)). Subsequent power output was higher in LW (2.95 +/- 0.24) and LC (2.91 +/- 0.25) than in CON (2.52 +/- 0.28 W kg(-1), P = 0.00, N = 8), yet final (T) over bar (c) remained lower. Pr e-cooling by ice-vest and cold air eff ectively reduced physiological and psychophysical strain and improved endur ance performance in the heat, irrespective of whether thighs were warmed or cooled. (C) 2001 Elsevier Science Inc. All rights reserved.