Differences in dry-bulb temperature do not influence moderate-duration exercise performance in warm environments when vapor pressure is equivalent.

Abstract

Recent studies have determined that ambient humidity plays a more important role in aerobic performance than dry-bulb temperature does in warm environments; however, no studies have kept humidity constant and independently manipulated temperature. Therefore, the purpose of this study was to determine the contribution of dry-bulb temperature, when vapor pressure was matched, on the thermoregulatory, perceptual and performance responses to a 30-min cycling work trial. Fourteen trained male cyclists (age: 32 ± 12year; height: 178 ± 6cm; mass: 76 ± 9kg; [Formula: see text]: 59 ± 9mLkg-1min-1; body surface area: 1.93 ± 0.12m2; peak power output: 393 ± 53W) volunteered, and underwent 1 exercise bout in moderate heat (MOD: 34.9 ± 0.2°C, 50.1 ± 1.1% relative humidity) and 1 in mild heat (MILD: 29.2 ± 0.2°C, 69.4 ± 0.9% relative humidity) matched for vapor pressure (2.8 ± 0.1kPa), with trials counterbalanced. Despite a higher weighted mean skin temperature during MOD (36.3 ± 0.5 vs. 34.5 ± 0.6°C, p < 0.01), none of rectal temperature (38.0 ± 0.3 vs. 37.9 ± 0.4°C, p = 0.30), local sweat rate (1.0 ± 0.3 vs. 0.9 ± 0.4mgcm-2min-1, p = 0.28), cutaneous blood flow (283 ± 116 vs. 287 ± 105 PU, p = 0.90), mean power output (206 ± 37 vs. 205 ± 41W, p = 0.87) or total work completed (371 ± 64 vs. 369 ± 70kJ, p = 0.77) showed any difference between environments during the work trial. However, all perceptual measures (perceived exertion, thermal discomfort, thermal sensation, skin wettedness, pleasantness, all p < 0.05) were affected detrimentally during MOD compared to MILD. In a warm and compensable environment, dry-bulb temperature did not influence high-intensity cycling performance when vapor pressure was maintained, whilst the perceptual responses were affected.