ECSS Paris 2023: OP-PN11
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.
Read CV Julien PériardECSS Paris 2023: OP-PN11
INTRODUCTION: Extreme heat events are becoming become more frequent and intense, with widespread impacts on health, wellbeing and performance (1, 2). It has been proposed that a physically active lifestyle could protect against heat-related impacts (4). Although heat loss responses are improved in trained individuals or by exercise training interventions (3), the effect of physical activity level on thermoregulatory function remains unclear. The objective of this study is to test the hypothesis that thermoregulatory function during heat stress is positively associated with physical activity levels. METHODS: Forty young adults (27 ± 8 y; 22 males and 18 females;) wore a tri-axial accelerometer for 7 consecutive days before being exposed to heat stress using the water perfused suit model. During heat stress, local sweat rate (LSR) was measured continuously until esophageal temperature increased by 1.2°C. Whole-body sweat rate (WBSR) was calculated from changes in nude body mass. Mean body temperature (Tb) was calculated as a weighted average of oesophageal and mean skin temperature to determine the activation threshold and thermosensitivity of LSR via segmented regression analysis. Pearson or Spearman correlations were then used to evaluate potential associations between average daily energy expenditure (EE) and time spent in moderate-vigorous physical activity (MVPA) and the LSR activation threshold and thmerosensitivity as well as WBSR. Analyses were further stratified by biological sex. RESULTS: There were no associations between EE or MVPA and the LSR activation threshold (EE: r=-0.06, p=0.360; MVPA: r=-0.079, p=0.314) and thermosensitivity (EE: r=0.17, p=0.153; MVPA: r=0.098, p=0.275). In contrast, WBSR was associated with EE (r=0.46, p < 0.001) and MVPA (r=0.27, p=0.048). When stratified by sex, WBSR was associated with EE in females (r=0.616, p=0.003) but males (r=0.036, p=0.440). CONCLUSION: These results suggest that physical activity levels are associated with whole-body sweat rate during passive heat stress, specifically amongst females. In contrast, physical activity levels are not associated with the thermoregulatory control of local sweat rate. References: 1. Meehl GA, Tebaldi C. More intense, more frequent, and longer lasting heat waves in the 21st century. Science. 2004;305(5686):994-7. 2. Romanello M, Walawender M, Hsu SC, Moskeland A, Palmeiro-Silva Y, Scamman D, et al. The 2024 report of the Lancet Countdown on health and climate change: facing record-breaking threats from delayed action. Lancet. 2024;404(10465):1847-96. 3. Cramer MN, Gagnon D, Laitano O, Crandall CG. Human temperature regulation under heat stress in health, disease, and injury. Physiol Rev. 2022;102(4):1907-89. 4. Deshayes TA, Périard JD. Regular physical activity across the lifespan to build resilience against rising global temperatures. eBioMedicine. 2023;96.
Read CV Amine DahhakECSS Paris 2023: OP-PN11
INTRODUCTION: Internal cooling strategies are widely used and have proven efficiency for mitigating thermal strain in intermittent sports during major events in the heat1-2. However, ice slushy ingestion may reduce sweat rate3 potentially impairing evaporative heat loss. Ice slushy implementation could also induce gastrointestinal discomfort in athletes4. As palatability and sensory properties can modulate thermal perception and tolerance, this study investigated the impact of different ice slushy flavors on physiological, perceptual, and performance responses during cycling repeated-sprint sessions in the heat. METHODS: In a crossover design, seventeen world-class female rugby seven players performed three cycling repeated-sprint sessions (three sets of five 6-s sprints; 24-s and 3-min inter-repetition and inter-set recovery, respectively) in the heat (38°C; 43% relative humidity) with ad libitum water and additional 2×150 g (before and mid-session) of either water (CON) or two isocaloric ice slushies: mint syrup (ICE-M) or grape juice (ICE-G). Performance was measured via peak and mean power output (PPO and MPO, respectively), along with sweat rate (SR) and perceptual ratings assessing pleasure, thermal comfort, and gastrointestinal symptoms (GIS). RESULTS: Ad libitum water intake was not different between conditions (p>0.69). No significant main effects were found for PPO and MPO (all p>0.37). SR was significantly different between conditions (p=0.03) driven by a lower SR in the ICE-G condition compared to both CON and ICE-M but without post-hoc analysis significances (CON−ICE-G pHolm=0.08; ICE-G−ICE-M pHolm=0.08; CON−ICE-M pHolm=0.69). Regarding perceptual ratings, thermal comfort was significantly higher for ICE-M compared to ICE-G (pHolm<0.01) and CON (pHolm<0.01) but without any effect on pleasure (p=0.43). While immediate post-session GIS showed no significant effects (p=0.14), GIS post-12 h and post-24 h were significantly higher for ICE-G compared to CON (pHolm=0.01; pHolm=0.02, respectively). No post-hoc analysis significances were observed between ICE-M and CON, or between ICE-G and ICE-M (all pHolm>0.12). Paired Hedges’ g visual estimation plots (ΔCON−ICE-G minus ΔCON−ICE-M) highlighted substantial individual variability for pleasure and all GIS time points. CONCLUSION: In this study, minty ice slushy appeared to be the optimal choice for improving thermal comfort in the heat. Compared to ad libitum water and grape juice ice slushy, it does not reduce the sweat rate, thus preserving evaporative thermoregulation. It also did not induce gastrointestinal symptoms post-session. These findings guided the strategy selected by the supporting staff for the Olympic Games; however, the high inter-individual variability observed in pleasure and gastrointestinal symptoms highlights the benefit of pre-competition testing before major sporting events. 1. Racinais et al. 2023 2. Katagiri et al. 2025 3. Morris et al. 2016 4. Naito et al. 2022
Read CV Camille PrecartECSS Paris 2023: OP-PN11