Relationship of Environmental, Physiological, and Perceptual Heat Stress Indices in Iranian Men

BACKGROUND: Heat stress is a known occupational hazard, which cause reduced exercise capacity. The purpose of this study was to evaluate the relationship among environmental, physiological, and perceptual heat stress indices in Iranian men. METHODS: This analytical study was carried out on 24 healthy men (age 23.34 ± 1.64 years) with normal body weight (body mass indices 21–25 kg/m(2)) in low workload for 120 min under hot climates (22–32°C, 40% relative humidity). Physiological strain index (PSI), wet-bulb globe temperature (WBGT), oral temperature, heart rate (HR), and heat strain score index (HSSI) questionnaires were simultaneous measurements taken at any 5 min during the exposure and resting state the initial measurements. RESULTS: The results showed that the range of WBGT index was 20.47–31.40°C. Significant correlation were found among WBGT and HSSI (r = 0.995), PSI (r = 0.990), oral temperature (r = 0.991), and HR (r = 0.972) indices. Also, significant correlation were found among HSSI and oral temperature (r = 0.983), HR (r = 0.978), and PSI (r = 0.987). CONCLUSIONS: The results have shown that simultaneous with the increase in valid indices of heat stress such as WBGT and PSI indices, the amount of HSSI has also increased with high power. Therefore, when there is no access to a reliable heat stress method such as WBGT, or PSI indices, HSSI, an observative and subjective heat strain method, can be used as a simple, fast in least 5 min, and inexpensive for evaluating the heat strain in Iranian men.