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

Purpose 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. Methods Fourteen trained male cyclists (age: 32 +/- 12 year; height: 178 +/- 6 cm; mass: 76 +/- 9 kg; V & x2d9;O2: 59 +/- 9 mL kg(-1) min(-1); body surface area: 1.93 +/- 0.12 m(2); peak power output: 393 +/- 53 W) volunteered, and underwent 1 exercise bout in moderate heat (MOD: 34.9 +/- 0.2 degrees C, 50.1 +/- 1.1% relative humidity) and 1 in mild heat (MILD: 29.2 +/- 0.2 degrees C, 69.4 +/- 0.9% relative humidity) matched for vapor pressure (2.8 +/- 0.1 kPa), with trials counterbalanced. Results Despite a higher weighted mean skin temperature during MOD (36.3 +/- 0.5 vs. 34.5 +/- 0.6 degrees C, p < 0.01), none of rectal temperature (38.0 +/- 0.3 vs. 37.9 +/- 0.4 degrees C, p = 0.30), local sweat rate (1.0 +/- 0.3 vs. 0.9 +/- 0.4 mg cm(-2) min(-1), p = 0.28), cutaneous blood flow (283 +/- 116 vs. 287 +/- 105 PU, p = 0.90), mean power output (206 +/- 37 vs. 205 +/- 41 W, p = 0.87) or total work completed (371 +/- 64 vs. 369 +/- 70 kJ, 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. Conclusion 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.