Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, LE11 3TU, UK.
Department of Health and Life Sciences, Coventry University, Oxford, UK.
Eur J Appl Physiol. 2021 Jun;121(6):1701-1713. doi: 10.1007/s00421-021-04642-3. Epub 2021 Mar 7.
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.
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), rectal temperature (T), temperature sensation (TS) and thermal comfort (TC) were measured throughout. Various forms of the PSI-index were assessed including the original PSI, PSI, adaptive-PSI (aPSI) and a version comprised of a measure of heat storage (PSI). 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).
Final PSI, PSI, aPSI, PSI did not differ between TTL and C (p > 0.05). However, differences between TTL and C occurred in final T, T-T, TS, TC and ROC in PSI, T, T and HR (p < 0.05).
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.
生理应激指数（PSI）旨在评估个体的热应激水平，但目前支持其用于识别可能达到热耐受极限（TTL）个体的证据有限。本研究旨在评估 PSI 是否可以识别有达到 TTL 风险的个体。
15 名女性和 21 名男性共进行了 136 次试验，每次试验包括两个 40-60 分钟的跑步机行走期，中间间隔约 15 分钟的休息时间，穿着透气或不透气的衣服，在一系列气候条件下进行。在整个过程中测量心率（HR）、皮肤温度（T）、直肠温度（T）、温度感觉（TS）和热舒适度（TC）。评估了 PSI 指数的各种形式，包括原始 PSI、PSI、自适应 PSI（aPSI）和包含热储存测量的版本（PSI）。在试验期间和试验最后 10 分钟内比较了完成试验（C，101 次试验）和提前终止试验（TTL，35 次试验）的最终生理和 PSI 值及其变化率（ROC）。
在 TTL 和 C 之间，最终 PSI、PSI、aPSI 和 PSI 没有差异（p > 0.05）。然而，在 TTL 和 C 之间，最终 T、T-T、TS、TC 和 PSI 的 ROC、T、T 和 HR 发生了差异（p < 0.05）。
这些结果表明，PSI 的各种形式并不能可靠地识别即将达到 TTL 的个体，因此其作为生理安全指数的有效性值得怀疑。然而，生理-知觉应激指数可能提供更有效的衡量标准。
