Are current heat guidelines for outdoor sports putting athletes at risk?

This study evaluates whether the current thermal safety thresholds used in outdoor sports guidelines are scientifically valid and safe for athletes under extreme heat conditions. With climate change making extreme heat more common, safeguarding athletes from heat-related illnesses is critical. Yet many current thresholds lack strong physiological validation. This study uses advanced simulation modeling to fill that evidence gap without the logistical and ethical difficulties of experimenting with athletes in severely hot environments.

The authors used the joint system thermoregulation model (JOS-3) to simulate core body temperatures in 29 experiments, covering six Olympic sports (namely football, marathon, rowing, rugby sevens, tennis and triathlon). They generated thousands of environmental and physiological condition combinations to predict whether thresholds would result in potentially hazardous core temperatures.

Findings show that the current heat thresholds for marathons, triathlons, and football may allow core temperatures to exceed 40°C, a marker of exertional heat stroke. These simulations therefore suggest to revise these thresholds, i.e. revise from WBGT 28°C to 24–27°C for marathon, revise from wet bulb globe temperature (WBGT) 32°C to 29–31°C or not revise for football, revise from WBGT 32.2°C to 23–26°C for triathlon. As current heat guidelines may not be conservative enough, revising these thresholds is necessary, and if not possible, the authors recommend implementing stronger mitigation strategies like schedule changes, more medical resources, and cooling protocols.

CITE: Oyama, T., Fujii, M., Nakajima, K., Takakura, J. Y., & Hijioka, Y. (2024). Validation of upper thermal thresholds for outdoor sports using thermal physiology modelling. Temperature, 11 (1), 92-106. doi: 10.1080/23328940.2023.2210477

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