Reliability of Perceptual Measures During and After Exercise in the Heat

Abstract

Research conducted with individuals exercising in the heat often includes perceptual ratings such as thirst sensation, thermal sensation, and rating of perceived exertion. The reliability of these measures during and after exercise heat stress is not well understood. PURPOSE: To assess the reliability of perceptual ratings of thirst, thermal sensations, and perceived exertion during and after exercise in the heat. METHODS: Eleven males and seven females (mean ± SD age, 23 ± 2 y; mass, 72.02 ± 10.33 kg; body fat, 16.2 ± 6.2 %) performed identical exercise on two occasions (separated by 8 ± 4 days). After walking (3.5 mph, 5% incline) in the heat (35.1 ± 2.3°C, 44 ± 7% RH) for 120 minutes, subjects sat in a thermoneutral environment (~22°C) for 135 min. During the first 45 min post-exercise subjects consumed a volume of water equal to 150% of sweat losses. Rating of perceived exertion (RPE), thermal, and thirst sensations were assessed every 30 min during exercise, every 15 min during the first 45 min after exercise (during rehydration), and every 30 min during the 90 min post-rehydration. Reliability of perceptual measures during (RPE, thermal and thirst sensations) and after (thermal and thirst sensations) exercise between the two trials were assessed with Bland-Altman plots [mean bias and limits of agreement (LOA)], correlation coefficients (r), intraclass correlation coefficient (ICC), and standard error of the mean (SEM). A reliable measure was defined as having a mean bias between −1 and 1 and a LOA less than ± 3. RESULTS: Mean bias, LOA, r, ICC and SEM for RPE during exercise were 0.55, ±2.87, 0.82, 0.88, and 0.78, respectively. Thermal sensation mean bias, LOA, r, ICC and SEM during exercise were 0.21, ±0.98, 0.73, 0.84, and 0.27, respectively; the same reliability measures post exercise were −0.24, ±1.65, 0.64, 0.68, and 0.49, respectively. Thirst sensation mean bias, LOA, r, ICC and SEM during exercise were 0.39, ±2.55, 0.87, 0.86, and 0.70, respectively; the same measures post exercise were −0.13, ±2.33, 0.88, 0.92, and 0.62, respectively. CONCLUSIONS: RPE was reliable during exercise heat stress; thermal sensation was reliable during and after exercise. Thirst sensation had greater variability (i.e., larger LOA) then thermal sensation during and after exercise but remained in defined reliability limits.