Pre-exercise and inter-bout palm cooling enhances intermittent sprint performance despite no thermoregulatory advantage during exercise in the heat

This study investigated whether palm cooling applied before exercise and during inter-bout recovery enhances intermittent sprint performance by improving thermoregulatory and perceptual responses during exercise in the heat (32°C, 60% RH). Nine physically active men completed two experimental trials in a randomized crossover design: a control (CON) and palm cooling (COOL; 12°C) condition. In each trial, participants performed two identical exercise bouts consisting of 30 min of cycling at 50% of peak power output followed by an intermittent sprint protocol (10 × 5-s maximal sprints interspersed with 25 s of unloaded pedaling and 30 s of passive recovery). In the COOL condition, palm cooling was applied before the first exercise bout and again during the 15-min recovery period separating the two exercise bouts. The mean and peak power outputs during the sprint protocol were significantly higher in the COOL condition than in the CON condition (p < 0.01). Palm skin temperature and skin blood flow were significantly lower, accompanied by improved thermal sensation, thermal comfort, and perceived exertion (p < 0.05). In contrast, rectal temperature, mean skin temperature, forehead deep temperature, heart rate, sweat loss, and dehydration did not differ between the conditions (p > 0.05). These findings demonstrate that palm cooling applied before exercise and during recovery enhances intermittent sprint performance in the heat, despite the absence of measurable thermoregulatory or cardiovascular benefits. Therefore, the ergogenic effect may be associated with improved perceptual responses rather than a reduction in systemic physiological strain.