Limited benefit of repeated post-exercise hot water immersion on exercise performance of well-trained cyclists in warm and hot conditions.

purposeThis study investigated the effects of daily hot water immersion after exercise in cool conditions on the physiological, perceptual, and endurance performance responses of well-trained cyclists in warm and hot conditions.

methodsSixteen male cyclists completed a six-day intervention involving daily cycling exercise for 40 min at 50% of their peak power output at 13.9 ± 0.1 °C, 43.9 ± 5.9% RH followed immediately by either hot water immersion (HWI; n = 8) or thermoneutral water immersion (CON; n = 8) for 40 min. At baseline and post-intervention, participants completed two 30-min continuous cycling tests followed by 20-km time-trial tests on two different days (first at 27.0 ± 0.2 °C, 42.2 ± 3.3% RH and 48 h later at 35.0 ± 1.2 °C, 35.5 ± 3.4% RH).

resultsHot water immersion decreased peak heart rate (p = 0.03), peak thermal sensation (p < 0.01), and peak rating of perceived exertion (p = 0.02) during the 30-min continuous test at 27 °C, and also decreased peak thermal sensation (p = 0.03) and peak rating of perceived exertion (p = 0.01) during the same test at 35 °C. None of these variables was altered in the CON group. The HWI intervention did not affect the time-trial performance in either condition.

conclusionThe findings that post-exercise hot water immersion for six consecutive days had no significant impact on the functioning of the cardiovascular and thermoregulatory systems or endurance performance in the heat suggest that this heat acclimation protocol cannot serve as an effective alternative to active heat acclimation in endurance-trained male individuals.