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Relationship between core temperature, skin temperature, and heat flux during exercise in heat

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Abstract

Purpose

This paper investigates the relationship between core temperature (T c), skin temperature (T s) and heat flux (HF) during exercise in hot conditions.

Method

Nine test volunteers, wearing an Army Combat Uniform and body armor, participated in three sessions at 25 °C/50 % relative humidity (RH); 35 °C/70 % RH; and 42 °C/20 % RH. Each session consisted of two 1-h treadmill walks at ~350 W and ~540 W intensity. T s and HF from six sites on the forehead, sternum, pectoralis, left rib cage, left scapula, and left thigh, and T c (i.e., core temperature pill used as a suppository) were measured. Multiple linear regressions were conducted to derive algorithms that estimate T c from T s and HF at each site. A simple model was developed to simulate influences of thermal conductivity and thickness of the local body tissues on the relationship between T c, T s, and HF.

Results

Coefficient of determination (R 2) ranged from 0.30 to 0.88, varying with locations and conditions. Good sites for T c measurement at surface were the sternum, and a combination of the sternum, scapula, and rib sites. The combination of T s and HF measured at the sternum explained ~75 % or more of variance in observed T c in hot environments. The forehead was found unsuitable for exercise in heat due to sweating and evaporative heat loss. The derived algorithms are likely applicable only for the same ensemble or ensembles with similar thermal and vapor resistances.

Conclusion

Algorithms for T c measurement are location-specific and their accuracy is dependent, to a large degree, on sensor placement.

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Acknowledgments

We would like thank to the volunteers who endured the experimental heat trials. We would also like to thank Dr. Reed Hoyt for his critical review and comments of this manuscript. We would like to acknowledge and thank Mr. Stephen Mullen, Patel Tejash, Timothy Rioux, Julio Gonzalez, William Tharion, Alex Welles, and Ms. Laurie Blanchard for their technical assistance in the collection, organization, and analysis of the study data.

Disclaimer

This study is approved for public release; distribution is unlimited. The opinions or assertions contained herein are the private views of the author(s) and are not to be construed as official or reflecting the views of the Army or the Department of Defense. The investigators have adhered to the policies for protection of human subjects as prescribed in Army Regulation 70-25, and the research was conducted in adherence with the provisions of 32 CFR Part 219. Human subjects participated in these studies after giving their free and informed voluntary consent. Investigators adhered to AR 70-25 and USAMRMC Regulation 70-25 on the use of volunteers in research. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations.

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Correspondence to Xiaojiang Xu.

Additional information

Communicated by George Havenith.

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Xu, X., Karis, A.J., Buller, M.J. et al. Relationship between core temperature, skin temperature, and heat flux during exercise in heat. Eur J Appl Physiol 113, 2381–2389 (2013). https://doi.org/10.1007/s00421-013-2674-z

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  • DOI: https://doi.org/10.1007/s00421-013-2674-z

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