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Potential Links Between Physiological and Perceptual Strain in High Heat Stress.

Xiujing Zhao·Brendon P McDermott·Wen-Juo Lo
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Abstract

The physiological strain index (PhSI) is widely used to quantify thermoregulatory and cardiovascular strain during heat stress. However, direct physiological measurements may not always be feasible in occupational or athletic settings. Therefore, this study aimed to examine the relationship and agreement between perceptual strain and integrated physiological strain indices during high heat stress. Ten healthy, physically active, non-heat-acclimated males (29 (7) yr; 1.79 (0.11) m; 77.4 (9.3) kg) completed two randomized crossover exercise trials in hot-dry (HD) and warm-humid (WH) environments with equivalent wet-bulb globe temperatures. Heart rate, rectal temperature, skin temperature, rating of perceived exertion, and thermal sensation were measured at baseline and every 15&#xa0;minutes during 60&#xa0;minutes of cycling. Physiological strain index (PhSI), adaptive physiological strain index (aPhSI), and perceptual strain index (PeSI) were calculated using validated equations. Repeated-measures correlation analyses demonstrated very strong associations between PeSI and both PhSI and aPhSI under HD (Rrm&#xa0;=&#xa0;0.940-0.943) and WH (Rrm&#xa0;=&#xa0;0.980-0.982; all p&#xa0;<&#xa0;0.001). Receiver operating characteristic analyses demonstrated good-to-excellent discrimination of physiological strain by PeSI (AUC&#xa0;=&#xa0;0.895-0.969). Mixed-effects analyses showed that higher PeSI values were associated with increased PhSI (&#x3b2;&#xa0;=&#xa0;1.325, p&#xa0;<&#xa0;0.001) and aPhSI (&#x3b2;&#xa0;=&#xa0;1.459, p&#xa0;<&#xa0;0.001). However, Bland-Altman analyses demonstrated relatively small mean biases (0.4-0.9 AU) but wide limits of agreement (-2.8 to 4.2 AU), indicating that PeSI and physiological strain indices are not interchangeable. These findings suggest that PeSI may serve as a practical adjunctive or screening indicator of physiological strain when direct physiological measurements are unavailable.

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HumansMaleHeart RateHot TemperatureAdultCross-Over StudiesBody TemperatureHeat Stress DisordersBody Temperature RegulationSkin TemperaturePhysical ExertionThermosensingPerceptionExerciseStress, Physiologicalheat strain indexperceivedsensationsubjective measuresthermoregulationJournal ArticleRandomized Controlled Trial

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Xiujing Zhao, Brendon P McDermott, Wen-Juo Lo. 2026. Potential Links Between Physiological and Perceptual Strain in High Heat Stress.. https://doi.org/10.1002/ejsc.70226

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Journal Article; Randomized Controlled Trial resourceAdult subjectCross-Over Studies subjectExercise subjectHeart Rate subjectHot Temperature subjectHumans subjectJournal Article subjectMale subjectPerception subjectRandomized controlled trials study

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