Context: Precooling and midevent cooling of the torso using cooling vests can improve exercise performance in the heat with or without physiological changes; however, the effects of such cooling during intermittent exercise in the heat are unknown. Objective: To investigate the effects of torso cooling during intermittent exercise in the heat (35°C, 50% relative humdity) on sprint performance and the physiological and perceptual responses to the exercise. Design Crossover study: Setting Walk-in environmental chamber. Patients or Other Participants: Ten non-heat-acclimated, male soccer players (age = 25 ± 2 years, height = 1.77 ± 0.06 m, mass = 72.9 ± 7.6 kg). Intervention(s): Two 90-minute bouts of soccer-specific intermittent running in the heat: 1 trial with a cooling vest worn during the exercise and 1 trial without a cooling vest. Each trial comprised two 45-minute periods separated by approximately 15 minutes of seated rest in cool conditions (approximately 23°C, 50% relative humdity). Main Outcome Measure(s): Peak sprint speed, rectal temperature (Tr), mean-weighted skin temperature (Tsk), heart rate (HR), rating of perceived exertion (RPE), and thermal sensation (TS) were measured every 5 minutes. Results: Peak sprint performance was largely unaffected by the cooling vest. The Tr, Tsk, HR, RPE, and TS were unaffected in the cooling-vest trial during the first 45 minutes, but Tr rose at a slower rate in the cooling-vest trial (0.026°C/min ± 0.008°C/min) than in the no-vest trial (0.032°C/min ± 0.009°C/min). During the second 45-minute period, Tr, Tr rate of rise, Tsk, RPE, and TS were lower in the cooling-vest trial (Hedges g range, 0.55-0.84), but mean HR was unaffected. Conclusions: Wearing a cooling vest during soccer-specific intermittent running in the heat reduced physiological and perceptual strain but did not increase peak sprint speed.
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