Effect of breathing cooled air during cycling on physiology and performance in the heat.

BACKGROUND: The aim of this study was to determine the physiological, perceptual, and exercise performance responses to breathing cooled air during and following exercise in the heat. METHODS: Twelve trained male cyclists (26±4 y; 180.5±5.6 cm; 56.4±7.5 mL/kg/min V̇O2max) cycled at 60% V̇O2max for 75 minutes, completed a 5-kilometer (5k) time trial, and recovered for 15 minutes in hot conditions (31 °C; 55% RH). Participants completed three separate trials in random order; breathing room air at a 1:4 (1 min on: 4 min off) ratio without ice (control [CON]), a 1:4 min ratio with ice (low-dose inhalation [LO]), and 1:1 min ratio with ice (high-dose inhalation [HI]). Intestinal temperature (TGI), heart rate (HR), blood pressure (BP), thirst, thermal sensation, rating of perceived exertion (RPE), and inspired air temperature were recorded every 15 minutes during cycling and five minutes during time trial and recovery. RESULTS: TGI (P=0.827), HR (P=0.363), Physiological Strain Index ([PSI], P=0.253), mean arterial pressure ([MAP] P=0.055) and thirst sensation (P=0.140) were not different between trials. Following the time trial, thermal sensation and RPE were significantly decreased in LO vs. CON and HI vs. CON (P≤0.039). Following the cooldown, thermal sensation was significantly decreased in HI vs. CON (P=0.006). Five-k time trial differences were not significant between groups (P≥0.098). CONCLUSIONS: Breathing cooled air during cycling in the heat did not provide a significant thermoregulatory or statistically significant performance advantage.