The impact of age and aging on exercise-induced thermoregulatory responses during a 15-km road race

OBJECTIVES: To assess the effect of age and aging on thermoregulatory responses during a 15-km road race under real-world conditions. DESIGN: Observational field study combining cross-sectional and longitudinal analyses during the 2008, 2009, and 2024 editions of a 15-km road race. METHODS: Data were collected in n = 57 participants for cross-sectional comparisons, and in n = 12 participants for longitudinal analyses, to determine the effects of age and aging, respectively. Ambient temperature across editions ranged from 8 to 12 °C. Intestinal core temperature (Tcore) and skin temperature (Tskin) were continuously measured, while metabolic heat production was estimated using running speed. RESULTS: Running speed and estimated metabolic heat production were higher in younger (29 [26-34] years, n = 28) versus older (65 [62-69] years, n = 29) runners (12.3 ± 1.9 versus 11.2 ± 1.6 km/h, p = 0.027; 15.1 ± 2.1 versus 14.0 ± 1.8 W/kg, p = 0.027, respectively), while sweat rates were similar. Start Tcore (37.4 ± 0.4 °C) increased to 38.8 ± 0.6 °C at the finish, with no differences between groups (p = 0.98). Older runners required more time to reach a steady state Tcore (37.0 ± 11.8 versus 27.2 ± 8.4 min, p = 0.003). Tskin at start and finish did not differ between groups. Start Tcore was lower after fifteen years of aging (37.3 ± 0.4 °C versus 37.7 ± 0.3 °C, p < 0.001). Finish Tcore (38.6 ± 0.6 °C versus 38.7 ± 0.7 °C, p = 0.38) and Tcore elevations (1.2 ± 0.3 °C versus 1.0 ± 0.6 °C, p = 0.20) remained unchanged, despite lower estimated metabolic heat production (13.8 ± 2.0 versus 15.7 ± 1.7 W/kg, p < 0.001). CONCLUSIONS: Thermoregulatory responses did not differ between younger and older runners, and Tcore elevations were comparable after fifteen years of aging. These findings indicate similar thermoregulatory responses during self-paced running in the cold across age groups and over fifteen years of aging.