Impact of different climatic conditions on peak core temperature of elite athletes during exercise in the heat: a Thermo Tokyo simulation study

Abstract

Objectives To evaluate how separate and combined climatic parameters affect peak core temperature during exercise in the heat using computer simulations fed with individual data. Methods The impact of eight environmental conditions on rectal temperature (T re) was determined for exercise under heat stress using the Fiala-thermal-Physiology-and-Comfort simulation model. Variations in ambient temperature (T a ±6°C), relative humidity (RH±15%) and solar radiation (SR+921 W/m 2) were assessed in isolation and combination (worst-case/best-case scenarios) and compared with baseline (T a 32°C, RH 75%, SR 0 W/m 2). The simulation model was fed with personal, anthropometric and individual exercise characteristics. Results 54 athletes exercised for 46±10 min at baseline conditions and achieved a peak core temperature of 38.9±0.5°C. Simulations at a higher T a (38°C) and SR (921 W/m 2) resulted in a higher peak T re compared with baseline (+0.6±0.3°C and +0.5±0.2°C, respectively), whereas a higher RH (90%) hardly affected peak T re (+0.1±0.1°C). A lower T a (26°C) and RH (60%) reduced peak T re by-0.4±0.2°C and a minor-0.1±0.1°C, respectively. The worst-case simulation yielded a 1.5±0.4°C higher T re than baseline and 2.0±0.7°C higher than the best-case condition. Conclusion Combined unfavourable climatic conditions produce a greater increase in peak core temperature than the sum of its parts in elite athletes exercising in the heat.