Effect of a Cooling Kit on Physiology and Performance Following Exercise in the Heat

Context: Exercising in the heat leads to an increase in body temperature that can increase the risk of heat illness or cause detriments in exercise performance. Objective: To examine a phase change heat emergency kit (HEK) on thermoregulatory and perceptual responses and subsequent exercise performance following exercise in the heat. Design: Two randomized crossover trials that consisted of 30 minutes of exercise, 15 minutes of treatment (T-1), performance testing (5-10-5 pro-agility test and 1500-m run), and another 15 minutes of treatment (T-2) identical to T-1. Setting: Outdoors in the heat (wet-bulb globe temperature: 31.5 degrees C [1.8 degrees C] and relative humidity: 59.0% [5.6%]). Participants: Twenty-six (13 men and 13 women) individuals (aged 20-27 y). Interventions: Treatment was performed with HEK and without HEK (control, CON) modality. Main Outcome Measures: Gastrointestinal temperature, mean skin temperature, thirst sensation, and muscle pain. Results: Maximum gastrointestinal temperature following exercise and performance was not different between trials (P >.05). Cooling rate was faster during T-1 CON (0.053 degrees C/min [0.049 degrees C/min]) compared with HEK (0.043 degrees C/min [0.032 degrees C/min]; P =.01). Mean skin temperature was lower in HEK during T-1 (P <.001) and T-2 (P =.05). T-2 thirst was lower in CON (P =.02). Muscle pain was lower in HEK in T-2 (P =.03). Performance was not altered (P >.05). Conclusions: HEK improved perception but did not enhance cooling or performance following exercise in the heat. HEK is therefore not recommended to facilitate recovery, treat hyperthermia, or improve performance.