Aural canal, esophageal, and rectal temperatures during exertional heat stress and the subsequent recovery period

Abstract

Context: The measurement of body temperature is crucial for the initial diagnosis of exertional heat injury and for monitoring purposes during a subsequent treatment strategy. However, little information is available about how different measurements of body temperature respond during and after exertional heat stress. Objective: To present the temporal responses of aural canal (Tac), esophageal (Tes), and rectal (Tre) temperatures during 2 different scenarios (S1, S2) involving exertional heat stress and a subsequent recovery period. Design: Randomized controlled trial. Setting: University research laboratory. Patients or Other Participants: Twenty-four healthy volunteers, with 12 (5 men, 7 women) participating in S1 and 12 (7 men, 5 women) participating in S2. Intervention(s): The participants exercised in the heat (42°C, 30% relative humidity) until they reached a 39.5°C cutoff criterion, which was determined by Tre in S1 and by Tes in S2. As such, participants attained different levels of hyperthermia (as determined by Tre) at the end of exercise. Participants in S1 were subsequently immersed in cold water (2°C) until Tre reached 37.5°C, and participants in S2 recovered in a temperate environment (30°C, 30% relative humidity) for 60 minutes. Main Outcome Measure(s): We measured Tac, Tes, and T re throughout both scenarios. Results: The Tes (S1 = 40.19 ± 0.41 °C, S2 = 39.50 ± 0.02°C) was higher at the end of exercise compared with both Tas (S1 = 39.74 ± 0.42°C, S2 = 38.89 ± 0.32°C) and Tre (S1 = 39.41 ± 0.04°C, S2 = 38.74 ± 0.28°C) (for both comparisons in each scenario, P < .001). Conversely, Tes (S1 = 36.26 ± 0.74°C, S2 = 37.36 ± 0.34°C) and Tas (S1 = 36.48 ± 1.07°C, S2 = 36.97 ± 0.38°C) were lower compared with Tre (S1 = 37.54 ± 0.04°C, S2 = 37.78 ± 0.31°C) at the end of both scenarios (for both comparisons in each scenario, P < .001). Conclusions: We found that Tas, Tes, and Tre presented different temporal responses during and after both scenarios of exertional heat stress and a subsequent recovery period. Although these results may not have direct practical implications in the field monitoring and treatment of individuals with exertional heat injury, they do quantify the extent to which these body temperature measurements differ in such scenarios. © by the National Athletic Trainers' Association, Inc.