Author(s): BATISTA OLIVEIRA, C., COSTA, J.A., PINTO, A., DORES, H., SOUSA, M., BRITO, J., Institution: NOVA MEDICAL SCHOOL, UNIVERSIDADE NOVA DE LISBOA, Country: PORTUGAL, Abstract-ID: 2386

INTRODUCTION:
Global warming and rising ambient temperatures pose significant challenges for outdoor sports, including football, by increasing the physiological risks associated with heat stress. Female referees are exposed to the same environmental challenges as football players; however, they are often overlooked, and their physiological response to exercise in the heat remains unknown. This study aimed to assess the effects of exercising in hot and humid (HEAT) compared to temperate (TEMP) conditions on the core temperature (Tc) and hydration status of female football referees.
METHODS:
Twelve female football referees (27.9 ± 5.1 y, Tier 3), users (n = 8) and non-users (n = 4) of hormonal contraceptives, performed a 90-minute exercise protocol with two 45-minute halves separated by a 15-minute break (SAFT90) in HEAT (ambient temperature [Ta], 31ºC; relative humidity [RH], 74%; Wet Bulb Globe Temperature [WBGT], 28ºC) and TEMP (22ºC Ta; 65% RH; 19ºC WBGT). The study had a randomised, crossover design and was conducted indoors. Menstrual cycle and hormonal contraceptive use were tracked. Users of hormonal contraceptives were tested during the taking phase, while naturally menstruating participants were mostly tested during the luteal phase. Tc was recorded continuously via ingestible telemetric capsules (BodyCAP). Hydration status was assessed by urine specific gravity (USG), saliva osmolality (SOSM), body mass loss, sweat rate, and sweat sodium concentration [Na+]. Four participants did not complete the study due to knee pain (n = 2) or not tolerating the humid heat (n = 2). Their available data were included in the analysis. Data were analysed using linear mixed-effects models and are presented as mean and 95% confidence intervals.
RESULTS:
The participants started both exercise sessions in a euhydrated state (USG: 1.012 ± 0.006; SOSM: 64.6 ± 12.3 mOsm). During exercise, the peak Tc reached was higher in HEAT (39.0ºC [38.7, 39.2] vs 38.5ºC [38.2, 38.9]; p = .006). A Tc value of 39.0ºC was reached or exceeded by two participants in TEMP and by eight in HEAT. Overall, the peak Tc was 39.3ºC among those who fully completed the study and 39.5ºC among those who did not. Peak values were mainly reached during the first half (between minutes 17 and 47), except for two participants in HEAT (minutes 85 and 95). The mean Tc values (38.3ºC [38.1, 38.6] vs 38.0ºC [37.8, 38.2]; p = .017) and the sweat rate (0.9 L/h [0.7, 1.0] vs 0.6 L/h [0.6, 0.7]; p = .004) were both higher in HEAT. Neither body mass loss (HEAT: 1.1% [0.8, 1.4] vs TEMP: 1.2% [1.0, 1.5]; p = .558) nor saliva osmolarity (HEAT: 92.8 [80.2, 105.4] vs TEMP: 94.3 [78.5, 110.0]; p = 1.000) differed between conditions. Similarly, the sweat [Na+] was not impacted by HEAT (HEAT: 36.6 mmol/L [24.5, 48.6] vs TEMP: 32.8 mmol/L [17.7, 48.0]; p = .387).
CONCLUSION:
Exposure to hot and humid conditions during a 90-minute exercise protocol increased both thermal strain and sweat rate in female football referees relative to temperate conditions.