title: Perceived exertion is as effective as the perceptual strain index in predicting physiological strain when wearing personal protective clothing.
abstract: The perceptual strain index (PeSI) has been shown to overcome the limitations associated with the assessment of the physiological strain index (PSI), primarily the need to obtain a core body temperature measurement. The PeSI uses the subjective scales of thermal sensation and perceived exertion (RPE) to provide surrogate measures of core temperature and heart rate, respectively. Unfortunately, thermal sensation has shown large variability in providing an estimation of core body temperature. Therefore, the primary aim of this study was to determine if thermal comfort improved the ability of the PeSI to predict the PSI during exertional-heat stress.
  
  
  
  Eighteen healthy males (age: 23.5years; body mass: 79.4kg; maximal aerobic capacity: 57.2ml·kg-1·min-1) wore four different chemical/biological protective garments while walking on treadmill at a low (<325W) or moderate (326-499W) metabolic workload in environmental conditions equivalent to wet bulb globe temperatures 21, 30 or 37°C. Trials were terminated when heart rate exceeded 90% of maximum, when core body temperature reached 39°C, at 120min or due to volitional fatigue. Core body temperature, heart rate, thermal sensation, thermal comfort and RPE were recorded at 15min intervals and at termination. Multiple statistical methods were used to determine the most accurate perceptual predictor.
  
  
  
  Significant moderate relationships were observed between the PeSI (r=0.74; p<0.001), the modified PeSI (r=0.73; p<0.001) and unexpectedly RPE (r=0.71; p<0.001) with the PSI, respectively. The PeSI (mean bias: -0.8±1.5 based on a 0-10 scale; area under the curve: 0.887), modified PeSI (mean bias: -0.5±1.4 based on 0-10 scale; area under the curve: 0.886) and RPE (mean bias: -0.7±1.4 based on a 0-10 scale; area under the curve: 0.883) displayed similar predictive performance when participants experienced high-to-very high levels of physiological strain.
  
  
  
  Modifying the PeSI did not improve the subjective prediction of physiological strain. However, RPE provided an equally accurate prediction of physiological strain, particularly when high-to-very high levels of strain were observed. Therefore, given its predictive performance and user-friendliness, the evidence suggests that RPE in isolation is a practical and cost-effective tool able to estimate physiological strain during exertional-heat stress under these work conditions.
authors.affiliation: Institute of Health and Biomedical Innovation, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane 4059, Queensland, Australia. Electronic address: dn.borg@qut.edu.au.
authors.forename: David N
authors.initials: DN
authors.lastname: Borg
authors.affiliation: Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth PO1 2ER, United Kingdom.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Costello
authors.affiliation: Institute of Health and Biomedical Innovation, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane 4059, Queensland, Australia.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Bach
authors.affiliation: Institute of Health and Biomedical Innovation, School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane 4059, Queensland, Australia.
authors.forename: Ian B
authors.initials: IB
authors.lastname: Stewart
mesh_terms: D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology*; D004777:Environment; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D010465:Perception / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011237:Predictive Value of Tests; D011481:Protective Clothing; D011601:Psychophysics; D012372:ROC Curve; D013312:Stress, Physiological / Q000502:physiology*; D016526:Workload; D055815:Young Adult
keywords: Perceived exertion; Psychophysiological measures; Subjective indices; Thermal behaviour; Thermoregulation