Abstract
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; \(\dot{V}{\text{O}}_{{{2}\,{\max}}}\): 59 ± 9 mL kg−1 min−1; body surface area: 1.93 ± 0.12 m2; peak power output: 393 ± 53 W) 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 ± 0.1 kPa), with trials counterbalanced.
Results
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 ± 0.4 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.
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Abbreviations
- BSA:
-
Body surface area
- CVR:
-
Cutaneous vascular resistance
- η p 2 :
-
Partial eta-squared
- E max :
-
Maximal evaporative capacity of the environment
- E req :
-
Required evaporative cooling for heat balance
- HR:
-
Heart rate
- HSI:
-
Heat strain index
- LSR:
-
Local sweat rate
- MAP:
-
Mean arterial pressure
- PETCO2 :
-
Partial pressure of end-tidal CO2
- \(\dot{Q}\) :
-
Cardiac output
- \(\dot{Q}_{{{\text{sk}}}}\) :
-
Skin blood flow
- RER:
-
Respiratory exchange ratio
- RPE:
-
Rating of perceived exertion
- SV:
-
Stroke volume
- T core :
-
Core body temperature
- T rec :
-
Rectal temperature
- \(\bar{T}_{{{\text{sk}}}}\) :
-
Mean skin temperature
- \(\dot{V}{\text{O}}_{2}\) :
-
Rate of oxygen uptake
- \(\dot{V}{\text{O}}_{{{2}\,{\max}}}\) :
-
Maximal rate of oxygen uptake
- WBSR:
-
Whole-body sweat rate
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THL, ZJS, JDC and TM contributed to conceptualization and design. THL, AMCM, HZ, SRS and TM were responsible for data collection. THL, ZJS and TM were responsible for data analysis, interpretation and drafting of the article. AMCM, HZ, SRS, NK and JDC reviewed the article and provided critical feedback. All authors approved the final manuscript. There are no conflicts of interest to report.
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Lei, TH., Schlader, Z.J., Che Muhamed, A.M. et al. Differences in dry-bulb temperature do not influence moderate-duration exercise performance in warm environments when vapor pressure is equivalent . Eur J Appl Physiol 120, 841–852 (2020). https://doi.org/10.1007/s00421-020-04322-8
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DOI: https://doi.org/10.1007/s00421-020-04322-8