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Beat the Heat – a hot bath after exercise boosts performance in the heat

We are all familiar with the no-pain-no-gain images of hardy Olympic athletes plunging into post-race ice baths ─ but our new findings show there may be another path to greatness.

In our new paper in Scandinavian Journal of Medicine and Science in Sports we show that swapping the ice bath for a soak in a hot bath triggers performance boosting adaptations mimicking how the body adjusts to hot weather.

Beat the heat - Train cool - bathe hot

Taking a hot bath after exercise for six days reduced both resting and exercising body temperature and improved running performance in the heat by 4.9%.

We believe that, for athletes who compete in the heat, the new mantra should be "Train-Cool, Bathe-Hot".

Heat is the enemy of performance

Athletes often perform in the heat ─ but heat is the enemy of performance. The body sweats in order to cool down, but this puts extra strain on the cardiovascular system leading to fatigue and a decrease in performance. To combat this, athletes typically acclimate by training for 10 to 14 days in the heat. The result of this ‘heat acclimation’ is a drop in body temperature, an expansion of blood plasma volume (the liquid part of blood) and an increase in sweat rate. These adaptations enhance the athlete’s ability to perform in the heat.

Heat acclimation

Unfortunately, heat acclimation usually involves relocating to a hot country for training or, for the lucky few, daily training in an environmental chamber, simulating a hot environment. These options are neither cheap nor practical. This inspired me and my team at Bangor University to explore more practical options. My interest in the benefits of a hot bath after exercise date back to my days as a competitive road cyclist. I’d regularly take a hot bath after a long training ride, and it didn’t make sense to me as a physiologist why an ice bath would be helpful.

The benefits of a hot bath

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.

Researchers have found other potential fitness and health benefits of taking a hot bath. For example, recent research in animals shows that heat stress after exercise enhances fitness training adaptations at the cellular level. Animals exposed to exercise followed by heat stress had increased levels of mitochondrial enzymes in skeletal muscles. These changes contribute to improved fitness.

Recent research in animals shows that heat stress after exercise enhances fitness training adaptations at the cellular level

Another new study just published in the Journal of Physiology shows improved cardiovascular health (improvements in arterial stiffness, blood pressure etc.) in young adults who took a hot bath 4-5 times per week over 8 weeks. Together these findings suggest that a hot bath might be a useful treatment for people who can't do much exercise, such as the injured athlete or the elderly.

Our team in Bangor also suggest 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.

Ice baths

We recognise that this alternative heat acclimation strategy conflicts with current athlete practice, which includes taking an ice bath after exercise, known as "cryotherapy". However, the proposed benefits of cryotherapy for recovery after exercise and fitness adaptations have been questioned in a recent paper in the Journal of Physiology.

Practical applications

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 would recommend this as a safe approach when adopting our new heat acclimation strategy.

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