Effect Of Localized Cooling On Thermo-physiological Responses To Cycling-induced Hyperthermia During Recovery In Thermally-challenging Conditions

Abstract

PURPOSE: To determine the effects of a phase changing ice-vest and a palm-cooling device on rectal and mean skin temperatures, heart rate (HR), and perceived thermal comfort during a 60 minute recovery period following exercise in the heat. METHODS: Ten recreationally active men and women (25 ± 3 years, VO2 peak: 43.6 ± 7.5 mL·kg -1· min-1) cycled for 60 minutes at 50% VO2 peak on a friction-braked cycle ergometer while exposed to hot environmental conditions (36°C; 45% relative humidity). Following exercise, each subject donned an ice vest, used a palm-cooling device, or sat passively, in randomized order for 60 additional minutes while in hot environmental conditions. Rectal (Tre) and four-site (chest, tricep, quadriceps, calf)) skin (Tsk) temperatures, heart rate (HR), and perceived thermal comfort (TC) were measured every 5 min throughout exercise and recovery. RESULTS: Sixty minutes of cycling in hot environmental conditions elicited an elevation in Tre from baseline across all exercise bouts (PostTre: 38.29 ± .32 °C, Net Tre gain: 1.11 ± .34 °C). Reduction in mean Tsk during the recovery period was significantly greater with the ice vest than the non-cooling condition (MD = 1.20 ± .39 °C, p = 0.042), with specific differences at 10–30, 45, and 55 min of recovery (p < 0.05). Reduction in HR during recovery was found to be significantly greater with the ice vest than the non-cooling condition (MD = 8.5 ± 1.5 b·min-1, p = 0.001) with differences recorded at 5, 15, and 25–60 min of recovery (p < 0.05). Despite Tsk and HR differences, no significant Tre (p = 0.61) or perceived TC (p = 0.24) effects were found between the three recovery conditions. Use of the palm-cooling device was not statistically different than the non-cooling control in any variable measured. CONCLUSION: The use of a phase-changing ice vest following exercise, while still exposed to environmental heat stress, augmented Tsk and HR recovery. This may be attributed to the larger surface area exposed to the cooling stimulus compared to the palm-cooling device. However, this cooling technique was not effective in lowering Tre more than a non-cooling control, which arguably may play a greater role in hyperthermic fatigue. Furthermore, the use of palm-cooling was ineffective in providing thermo-physiological benefit during post-exercise recovery in a hot environment.