Hot bath or hot tub post-workout provides heat acclimation, study shows

Planning a winter getaway that includes a hot-climate race? Here’s a tip: jump in the hot tub (or alternatively, have a hot bath) after your daily run to prepare yourself for running in the heat. A study published this week in Frontiers in Physiology showed that hot water immersion after exertion resulted in significant heat acclimation in endurance-trained and recreational runners alike. A post-workout sauna may have a similar effect.

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The study was done with eight endurance-trained athletes and eight recreational runners running on a treadmill in a room heated to 19 C. None had been exposed to heat recently, and none were regular hot bath-takers after exercise.

Subjects ran at 65 per cent of VO2 max for 40 minutes on six consecutive days, followed by a hot bath at 40 C for up to 40 minutes. The runners’ heat acclimation was assessed both before the six-day experiment and afterwards, with a 40-minute treadmill run in a room heated to 33 C, measuring such variables as skin temperature, core temperature, onset of sweating, perceived exertion, end-exercise heartrate and exercise performance.

Taking a hot bath after exercise elicits heat acclimation adaptations in endurance trained @ProfNeilWalsh @JessicaAnneMee @MikeZurawlew https://t.co/FK1Iwwhgm7

— Extremes (@ERGbangor) December 18, 2018

The only heat-acclimation variable that was significantly different between the endurance-trained athletes and the recreational runners was that the recreational runners’ end-exercise heartrates were significantly lower after the experiment. The authors note that endurance athletes are considered to be already somewhat heat-acclimated due to the nature of training, and that their potential for improved acclimation may be less. Still, they benefitted from hot water immersion, and this could be a strategy for athletes to follow leading up to the Tokyo 2020 Olympics, which are forecasted to be extremely hot. And recreational athletes can benefit, too.