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Adding sleep restriction to the equation: impact on wildland firefighters’ work performance and physiology in hot conditions

Abstract

Purpose

To examine the effects of sleep restriction on firefighters’ physical task performance, physical activity, and physiological and perceived exertion during simulated hot wildfire conditions.

Methods

31 firefighters were randomly allocated to either the hot (n = 18, HOT; 33 °C, 8-h sleep opportunity) or hot and sleep restricted (n = 13, HOT + SR; 33 °C, 4-h sleep opportunity) condition. Intermittent, self-paced work circuits of six firefighting tasks were performed for 3 days. Firefighters self-reported ratings of perceived exertion. Heart rate, core temperature, and physical activity were measured continuously. Fluids were consumed ad libitum, and all food and fluids consumed were recorded. Urine volume and urine specific gravity (USG) were analysed and sleep was assessed using polysomnography (PSG).

Results

There were no differences between the HOT and HOT + SR groups in firefighters’ physical task performance, heart rate, core temperature, USG, or fluid intake. Ratings of perceived exertion were higher (p < 0.05) in the HOT + SR group for two of the six firefighting tasks. The HOT group spent approximately 7 min more undertaking moderate physical activity throughout the 2-h work circuits compared to the HOT + SR group.

Conclusion

Two nights of sleep restriction did not influence firefighters’ physical task performance or physiological responses during 3 days of simulated wildfire suppression. Further research is needed to explore firefighters’ pacing strategies during real wildfire suppression.

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Acknowledgements

We would like to acknowledge the Bushfire Co-operative Research Centre for providing logistical support for this project. We would like to thank all the firefighters that generously volunteered their time to participate in this research. Dr. Grace Vincent is supported by an Early Career Fellowship at Central Queensland University. Dr. Nicola D Ridgers was supported by an Australian Research Council Discovery Early Career Researcher Award (DE120101173). We acknowledge Eoin O’Connell for the development of the customized Excel macro and Dr. Jacqueline Tran for assistance with the statistical analyses.

Funding

This study was funded by the Bushfire Co-operative Research Centre (Grant name: Operational readiness of rural firefighters during bushfire suppression).

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Correspondence to Grace E. Vincent.

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Research involving human participants

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Conflict of interest

The authors declare they have no conflicts of interest.

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Vincent, G.E., Ferguson, S., Larsen, B. et al. Adding sleep restriction to the equation: impact on wildland firefighters’ work performance and physiology in hot conditions. Int Arch Occup Environ Health 91, 601–611 (2018). https://doi.org/10.1007/s00420-018-1304-9

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  • DOI: https://doi.org/10.1007/s00420-018-1304-9

Keywords

  • Firefighting
  • Sleep restriction
  • Physical performance
  • Heat
  • Physical activity