Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat

Joseph P. Bachraty, JianBo Qiao, Elizabeth S. Powers, Lesley W. Vandermark, J. Luke Pryor and Riana R. Pryor ()
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Joseph P. Bachraty: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA
JianBo Qiao: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA
Elizabeth S. Powers: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA
Lesley W. Vandermark: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA
J. Luke Pryor: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA
Riana R. Pryor: Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA

IJERPH, 2024, vol. 21, issue 3, 1-13

Abstract: This study compared physiological responses to two work/rest cycles of a 2:1 work-to-rest ratio in a hot environment. In a randomized crossover design, fourteen participants completed 120 min of walking and rest in the heat (36.3 ± 0.6 °C, 30.2 ± 4.0% relative humidity). Work/rest cycles were (1) 40 min work/20 min rest [40/20], or (2) 20 min work/10 min rest [20/10], both completing identical work. Core temperature (T c ), skin temperature (T sk ), heart rate (HR), nude body mass, and perception of work were collected. Comparisons were made between trials at equal durations of work using three-way mixed model ANOVA. T c plateaued in [20/10] during the second hour of work ( p = 0.93), while T c increased in [40/20] ( p < 0.01). There was no difference in maximum T c ([40/20]: 38.08 ± 0.35 °C, [20/10]: 37.99 ± 0.27 °C, p = 0.22) or end-of-work T sk ([40/20]: 36.1 ± 0.8 °C, [20/10]: 36.0 ± 0.7 °C, p = 0.45). End-of-work HR was greater in [40/20] (145 ± 25 b·min −1 ) compared to [20/10] (141 ± 27 b·min −1 , p = 0.04). Shorter work/rest cycles caused a plateau in T c while longer work/rest cycles resulted in a continued increase in T c throughout the work, indicating that either work structure could be used during shorter work tasks, while work greater than 2 h in duration may benefit from shorter work/rest cycles to mitigate hyperthermia.

Keywords: heat strain; work-to-rest ratio; intermittent work; hot environment; hyperthermia (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2024
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