Author(s): DAHHAK, A., PAMART, N., LEE, E., HSOUNA, H., OUBOUCHOU, K., DUMAIS, A., DESHAYES, T.A., GAGNON, D., Institution: MONTREAL HEART INSTITUTE, Country: CANADA, Abstract-ID: 1271

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:
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