Abstract
Introduction
Personal protective equipment (PPE) inhibits heat dissipation and elevates heat strain. Impaired cooling with PPE warrants investigation into practical strategies to improve work capacity and mitigate exertional heat illness.
Purpose
Examine physiological and subjective effects of forearm immersion (FC), fan mist (MC), and passive cooling (PC) following three intermittent treadmill bouts while wearing PPE.
Methods
Twelve males (27 ± 6 years; 57.6 ± 6.2 ml/kg/min; 78.3 ± 8.1 kg; 183.1 ± 7.2 cm) performed three 50-min (10 min of 40%, 70%, 40%, 60%, 50% vVO2max) treadmill bouts in the heat (36 °C, 30% relative humidity). Thirty minutes of cooling followed each bout, using one of the three strategies per trial. Rectal temperature (Tcore), skin temperature (Tsk), heart rate (HR), heart rate recovery (HRR), rating of perceived exertion (RPE), thirst, thermal sensation (TS), and fatigue were obtained. Repeated-measures analysis of variance (condition x time) detected differences between interventions.
Results
Final Tcore was similar between trials (P > .05). Cooling rates were larger in FC and MC vs PC following bout one (P < .05). HRR was greatest in FC following bouts two (P = .013) and three (P < .001). Tsk, fluid consumption, and sweat rate were similar between all trials (P > .05). TS and fatigue during bout three were lower in MC, despite similar Tcore and HR.
Conclusion
Utilizing FC and MC during intermittent work in the heat with PPE yields some thermoregulatory and cardiovascular benefit, but military health and safety personnel should explore new and novel strategies to mitigate risk and maximize performance under hot conditions while wearing PPE.
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Data availability
All data generated or analyzed during this study are included in this published article.
Abbreviations
- ACU:
-
Army combat uniform
- FC:
-
Forearm cooling
- HR:
-
Heart rate
- HRR:
-
Heart rate recovery
- HRV:
-
Heart rate variability
- MC:
-
Fan-mist cooling
- NBC:
-
Nuclear, biological, or chemical
- NBM:
-
Nude body mass
- PC:
-
Passive cooling
- PPE:
-
Personal protective gear
- ANOVA:
-
Analysis of variance
- RPE:
-
Rate of perceived exertion
- SD:
-
Standard deviation
- Tcore :
-
Rectal temperature
- Tsk :
-
Mean skin temperature
- TS:
-
Thermal sensation
- USG:
-
Urine-specific gravity
- VO2max:
-
Maximal volume of oxygen uptake
- VO2peak:
-
Peak value of oxygen uptake
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Acknowledgements
We would like to thank the U.S. Army Medical Research and Development Command for funding this study, as well as those who volunteered to participate.
Funding
This study was sponsored by the U.S. Army Medical Research and Development Command under a research contract with The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc.; Award No.: W81XWH-17–2-0024. The cooling device used for forearm immersion was developed by First Line Technologies (Chantilly, VA, USA) which is a corporate sponsor of the Korey Stringer Institute, where this project was conducted.
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Contributions
Conceptualization and design: [Margaret C. Morrissey, Ciara N. Manning, Tushar Gulati, Srinivas Laxminarayan, Jaques Reifman, Douglas J. Casa]; Data collection: [Sean P. Langan, Margaret C. Morrissey, Ciara N. Manning]; Data analysis: [Sean P. Langan]; Writing – original draft preparation: [Sean P. Langan]; Writing – review and editing: [Sean P. Langan, Margaret C. Morrissey, Ciara N. Manning, Tushar Gulati, Srinivas Laxminarayan, Jaques Reifman, Douglas J. Casa]; Funding acquisition: [Douglas J. Casa]; Supervision: [Douglas J. Casa]. All authors approved the final version of the manuscript.
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The Korey Stringer Institute focuses on exertional heat illnesses and research aimed at maximizing performance, optimizing safety, and preventing sudden death in athletes, warfighters, and laborers.
Ethics approval
This study was approved by the University of Connecticut Institutional Review Board and all procedures were in accordance with the Declaration of Helsinki. This study was also reviewed and approved by the U.S. Army Human Research Protections Office (Fort Detrick, MD).
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Informed consent was obtained from all individual participants included in the study.
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Communicated by Narihiko kondo.
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Langan, S.P., Manning, C.N., Morrissey, M.C. et al. Efficacy of two intermittent cooling strategies during prolonged work-rest intervals in the heat with personal protective gear compared with a control condition. Eur J Appl Physiol 123, 1125–1134 (2023). https://doi.org/10.1007/s00421-023-05139-x
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DOI: https://doi.org/10.1007/s00421-023-05139-x