Modified physiological equivalent temperature for monitoring heat stress: 20-year data from the Falmouth Road Race.

Wet-Bulb Globe Temperature (WBGT) is a commonly used tool for monitoring heat stress in outdoor endurance races. The Physiologically Equivalent Temperature (PET) and the Universal Thermal Climate Index (UTCI) have been proposed as alternatives to overcome WBGT's limitations, but PET also has shortcomings and needs improvement for effective use as a screening tool. The aim is to identify the best predictor for Exertional Heat Illness (EHI) and Exertional Heat Stroke (EHS) in outdoor races. Based on a 20-year dataset from the Falmouth Road Race, generalized linear regression was used to analyze the relationship between the incident rate and the predictors, and model performance was evaluated by leave-one-out cross-validation. The modified version of PET, mPET, had the highest explanation for EHI rate at 59%, with WBGT at 45.7%. UTCI and PET had the lowest explanatory power, 21% and 17.9% respectively. For EHS, WBGT had the highest explanatory power at 58.1%, and mPET followed with 49.1%. In cross-validation for EHI, the predicted values of mPET strongly correlated with the actual values (cor = 0.767, p < 0.05). In cross-validation for EHS, the predicted values of WBGT significantly correlated with the actual values (cor = 0.604, p < 0.05). Overall, mPET is a superior predictor for EHI rate compared with PET, WBGT and UTCI, but for EHS rate, further research is needed to identify the best predictor.