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

Bachraty, Joseph P.; Qiao, JianBo; Powers, Elizabeth S.; Vandermark, Lesley W.; Pryor, J. Luke; Pryor, Riana R.

doi:10.3390/ijerph21030371

Open AccessArticle

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

by

Joseph P. Bachraty

,

JianBo Qiao

,

Elizabeth S. Powers

,

Lesley W. Vandermark

,

J. Luke Pryor

and

Riana R. Pryor

^*

Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY 14214, USA

^*

Author to whom correspondence should be addressed.

Int. J. Environ. Res. Public Health 2024, 21(3), 371; https://doi.org/10.3390/ijerph21030371

Submission received: 29 January 2024 / Revised: 12 March 2024 / Accepted: 18 March 2024 / Published: 20 March 2024

(This article belongs to the Special Issue The Impact of Extreme Weather and Climate on Human Health)

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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

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MDPI and ACS Style

Bachraty, J.P.; Qiao, J.; Powers, E.S.; Vandermark, L.W.; Pryor, J.L.; Pryor, R.R. Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat. Int. J. Environ. Res. Public Health 2024, 21, 371. https://doi.org/10.3390/ijerph21030371

AMA Style

Bachraty JP, Qiao J, Powers ES, Vandermark LW, Pryor JL, Pryor RR. Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat. International Journal of Environmental Research and Public Health. 2024; 21(3):371. https://doi.org/10.3390/ijerph21030371

Chicago/Turabian Style

Bachraty, Joseph P., JianBo Qiao, Elizabeth S. Powers, Lesley W. Vandermark, J. Luke Pryor, and Riana R. Pryor. 2024. "Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat" International Journal of Environmental Research and Public Health 21, no. 3: 371. https://doi.org/10.3390/ijerph21030371

APA Style

Bachraty, J. P., Qiao, J., Powers, E. S., Vandermark, L. W., Pryor, J. L., & Pryor, R. R. (2024). Plateau in Core Temperature during Shorter but Not Longer Work/Rest Cycles in Heat. International Journal of Environmental Research and Public Health, 21(3), 371. https://doi.org/10.3390/ijerph21030371

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

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