Hot bath after exercise improves performance in the heat

New research from Bangor University shows that taking a hot bath after exercise for 6 days reduces both resting and exercising body temperature and improves running performance in the heat. Prof Walsh, whose team lead the work, said “for sports people who compete in the heat, the new mantra should be: "train-cool, bathe-hot".

Athletes and those in physically demanding occupations, such as soldiers and fire fighters, are often required to perform in the heat. Exercise performance is reduced in the heat due to the increase in body temperature. The body sweats in order to cool down, but this puts extra strain on the cardiovascular system which, in turn, increases fatigue. Also, when exercising in the heat there is an increased risk of collapse due to exertional heat illness and the much more serious condition, heat stroke which can be fatal.

To combat this, athletes typically heat acclimatise by training for 10 to 14 days in the heat. Current practice involves relocating to train in a hot country or, for the lucky few with access, daily training in a simulated hot environment in an environmental chamber. These options are neither cheap nor practical.

This novel work by Prof Walsh’s team at Bangor University’s School of Sport, Health & Exercise Sciences, shows that simply taking a hot bath in 40°C water after exercise in temperate conditions on 6 successive days provides heat acclimation. This was shown as reduced body temperature at rest and during exercise and improved 5 km time trial performance during treadmill running in the heat.

As Prof Walsh explains: “The therapeutic benefits of hot water bathing have long been recognised ─ anyone with aching bones and muscles who has bathed at a Roman Spa will testify to this! Indeed, it was the writer Silvia Plath who in the Bell Jar said “I am sure there are things that can’t be cured by a good bath but I can’t think of one.””

The researchers highlight other potential health and fitness benefits of taking a hot bath after exercise beyond the pleasurable sensation of bathing aching muscles in hot water. For example, recent research from the University of Tokyo shows that heat stress after exercise can enhance fitness training adaptations at the cellular level in skeletal muscle. These changes in muscle are thought to contribute to improved fitness. The authors suggested that heat exposure might be a useful treatment for people who can't do much exercise, such as the elderly and injured athletes.

The team in Bangor also believe that a hot bath can stimulate the immune system which may be helpful for athletes as heavy exercise temporarily decreases immune function and increases the risk of infections such as the common cold.

They also recognise that this alternative heat acclimation strategy conflicts with current athlete practice, which includes taking an ice-bath after exercise, known as ‘cryotherapy’. But, Prof Walsh is quick to stress that the proposed benefits of cryotherapy for recovery after exercise and fitness adaptations have recently been questioned.

“Although participants in our study bathed for up to 40 minutes in 40°C water after exercise the benefits may be gained by bathing for as little as 20 minutes. We recommend a sensible and safe approach when adopting a heat acclimation strategy,” Prof Walsh said.

This study is published online ahead of print in Scandinavian Journal of Medicine & Science in Sports – Post-exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat. December 2015 DOI 10.1111/sms.12638

Publication date: 11 December 2015