Triathletes will do just about anything to acclimate for a hot race, from long sauna sessions to sweating in hot yoga to setting up the trainer in a garage on a sweltering summer day. But heat acclimation may be as simple as taking a soak. Research published in the Scandinavian Journal of Medicine in Science & Sports shows the bathtub is a straightforward and effective tool for building heat adaptations in endurance athletes.
In the study, non-heat acclimated athletes ran a 5K time trial in temperate and hot conditions, then took part in a six-day routine involving a 40-minute treadmill run followed by either a hot-water or room-temperature soak. At the conclusion of the week, they ran the time trial again—and there was a big difference between the two soaking sets when running in the heat.
“The normal decrease in performance over a 5K time trial was 5%,” says Professor Neil Walsh of Bangor University. “This decrease was prevented in those who heat acclimated.”
In other words, the ones who soaked in the hot tub after their workouts were able to run just as fast in hot weather as they were in mild conditions. Walsh says this is because heat acclimation, even in a tub, can lower resting body temperature and switch on the heat loss mechanisms (such as sweating) earlier during exercise in the heat.
Walsh says the benefits of this protocol may last at least two weeks. To implement this practice ahead of training or racing in a warmer climate, Walsh provides the following instructions:
- Train as usual, but allot time at the end of the workout for a soak.
- Take a hot bath for 15 minutes on day one, building 5 minutes per day, until 40 minutes on day six.
- The bath should be hot, but not as hot as you can stand—Walsh recommends 104 degrees Fahrenheit (40 degrees Celsius). If in doubt, get out.
- Immersion should reach up to the neck.