Author(s): PÉRIARD, J., CLARK, B., TAYLOR, B., GOUTTEBARGE, V., BROWN, H.A., Institution: UNIVERSITY OF CANBERRA, Country: AUSTRALIA, Abstract-ID: 493

INTRODUCTION:
Professional football, both domestically (e.g. Australia) and internationally (e.g. FIFA World Cup), is often played in hot summer conditions. To attenuate the risk of exertional heat illness, the Australian Professional Leagues implemented a new heat policy during the 2023-2024 season involving one to two drink/cooling breaks per half when wet-bulb globe temperature (WBGT) and/or ambient temperature exceeded 26ºC and 31ºC, respectively. This study monitored gastro-intestinal temperature (Tgi) and running characteristics during male and female A-League matches.
METHODS:
Twenty-seven (20 females) elite football players from two A-League Men’s (ALM) and three Women’s (ALW) teams were monitored in 24 matches (ALM: n = 11; ALW: n = 13) during the 2024-2025 season. Tgi was monitored continuously and rating of perceived exertion (RPE) and thermal sensation were recorded at match completion. Individual running characteristics were recorded using GPS and environmental conditions were recorded on site. Generalised additive mixed models were used to analyse Tgi and perceptual responses. Match running characteristics were analysed using linear mixed-effects models.
RESULTS:
Ambient temperature, relative humidity and WBGT for ALM were: 27.1 ± 4.9ºC, 57 ± 17% and 22.7 ± 3.9ºC; and for ALW: 29.2 ± 3.4ºC, 48 ± 18% and 24.7 ± 2.6ºC. Average Tgi during ALM and ALW matches was 38.9°C [38.6, 39.2] and 38.7°C [38.4, 39.0], respectively. During half-time, Tgi decreased by 0.6°C [0.2, 1.0] (P<0.01) for ALM and 0.8°C [0.5, 1.1] (P<0.01) for ALW. Average peak Tgi during ALM and ALW matches was 39.4°C [39.1, 39.6] and 39.0°C [38.8, 39.3], respectively. Peak Tgi was correlated with wet-bulb temperature (r=0.365, P<0.01) and WBGT (r=0.295, P=0.01). Match RPE was 15.4 [14.8, 16.4] for ALM and 16.0 [15.3, 16.6] for ALW. Match thermal sensation was 5.1 [4.8, 5.3] for ALM and 5.5 [5.3, 5.8] for ALW. Perceptual variables were correlated with WBGT (r=0.373–0.738, P≤0.01) and distance covered (r=0.257–0.484, P≤0.03). Total match running distance was 10,490 m [10,112, 10,861] for ALM and 10,366 m [10,074, 10,657] for ALW. WBGT did not significantly correlate with distance for ALM (P=0.69) or ALW (P=0.67). Distance at high intensity was 669 m [575, 763] for ALM and 472 m [391, 552] for ALW. WBGT did not significantly correlate with high intensity distance for ALM P=0.28) or ALW (P=0.11).
CONCLUSION:
The A-Leagues heat policy appears to protect most players from severe heat strain. While Tgi exceeded 40ºC in some instances, the prevalence was relatively low (7%). The WBGT where Tgi was >40ºC ranged from 22.8°C to 29.7°C and on two occasions this occurred during matches with drink/cooling breaks. As such, additional data with greater participant and environmental condition diversity are required to elucidate the relationship between the environment and the development of heat strain. Of note, our data reinforce that half-time is the most effective break/intervention for reducing core temperature.