The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limit

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Davey, SL, Downie, V, Griggs, K ORCID: https://orcid.org/0000-0002-1962-9613 and Havenith, G, 2021. The physiological strain index does not reliably identify individuals at risk of reaching a thermal tolerance limit. European Journal of Applied Physiology. ISSN 1439-6319

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Official URL: https://doi.org/10.1007/s00421-021-04642-3

Abstract

Purpose
The physiological strain index (PSI) was developed to assess individuals' heat strain, yet evidence supporting its use to identify individuals at potential risk of reaching a thermal tolerance limit (TTL) is limited. The aim of this study was to assess whether PSI can identify individuals at risk of reaching a TTL.

Methods
Fifteen females and 21 males undertook a total of 136 trials, each consisting of two 40-60 minute periods of treadmill walking separated by ~ 15 minutes rest, wearing permeable or impermeable clothing, in a range of climatic conditions. Heart rate (HR), skin temperature (T sk), rectal temperature (T re), temperature sensation (TS) and thermal comfort (TC) were measured throughout. Various forms of the PSI-index were assessed including the original PSI, PSI fixed , adaptive-PSI (aPSI) and a version comprised of a measure of heat storage (PSI HS). Final physiological and PSI values and their rate of change (ROC) over a trial and in the last 10 minutes of a trial were compared between trials completed (C, 101 trials) and those terminated prematurely (TTL, 35 trials).

Results
Final PSI original , PSI fixed , aPSI, PSI HS did not differ between TTL and C (p > 0.05). However, differences between TTL and C occurred in final T sk , T re-T sk , TS, TC and ROC in PSI fixed , T re , T sk and HR (p < 0.05).

Conclusion
These results suggest the PSI, in the various forms, does not reliably identify individuals at imminent risk of reaching their TTL and its validity as a physiological safety index is therefore questionable. However, a physiological-perceptual strain index may provide a more valid measure.

Item Type:	Journal article
Publication Title:	European Journal of Applied Physiology
Creators:	Davey, S.L., Downie, V., Griggs, K. and Havenith, G.
Publisher:	Springer Science and Business Media LLC
Date:	7 March 2021
ISSN:	1439-6319
Identifiers:	Number Type 10.1007/s00421-021-04642-3 DOI 1424333 Other
Rights:	© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Divisions:	Schools > School of Science and Technology
Record created by:	Jeremy Silvester
Date Added:	12 Mar 2021 10:33
Last Modified:	31 May 2021 15:05
URI:	https://irep.ntu.ac.uk/id/eprint/42495