A hot bath after a long walk or run on a cold winter’s day… Does that sound ideal? What you might not know is that bath might also have benefits for your health! Let’s hand over to Campbell Menzies, a PhD student at Coventry University (Faculty Research Centre for Sport, Exercise and Life Sciences) to explain!
Key question: Can having a hot bath improve my health?
The good news for bath lovers is that yes, regularly having a bath may have health benefits. Hot baths and saunas are forms of passive heating, which is when your body temperature is increased whilst not doing any exercise. This isn’t your typical evening bath though… Research protocols have typically involved water temperatures of 39-40 °C which is maintained (unlike your bath at home that gradually cools down) for 30-90 minutes.
Your internal body temperature (or core temperature) is normally around 37 °C. It is maintained by various processes, such as sweating (to cool you down) and shivering (to warm you up). The increase in body temperature caused by passive heating is a result of these processes being unable to deal with the external heat and maintain the “normal” temperature. “Normal” functioning of the body is called homeostasis and disturbances to homeostasis can lead to adaptations which help the body to cope with future disturbances. These adaptations can have health benefits. What health benefits can I get from passive heating?
The idea of using passive heating to improve health was used by the Ancient Greeks and Romans over 2000 years ago. In Finland, where sauna-bathing is common, a recent study showed that people who visit the sauna more regularly and have longer sauna-bathing sessions typically live for longer. Some other beneficial effects of regular passive heating are thought to be improved fitness, lower resting blood pressure, better functioning blood vessels, and improved metabolism of fat and sugars.
Does this mean passive heating can replace exercise?
As discussed in blog #16, not everyone likes exercise. But can passive heating replace exercise? A recent review concluded that there is some overlap in the health benefits that can be gained from passive heating when compared to exercise. However, before you scrap your exercise plan in favour of a Jacuzzi (as tempting as that sounds), here are a few things that you should remember:
1) Passive heating and weight loss
Not all the benefits of exercise can be obtained from passive heating and this includes weight loss. Changes in body weight are a result of long-term differences in energy intake versus energy expenditure (see blog #2). Exercise has a much larger effect on energy expenditure than passive heating and initial evidence suggests that passive heating has no effect on hunger hormones.
2) Comparisons between passive heating and exercise
Extended periods of passive heating can be hard to tolerate and even dangerous if not properly managed. Studies investigating passive heating have often used the largest tolerable dose of heating but this is often compared to small amounts of exercise. Even with the cards stacked in favour of passive heating, exercise remains superior regarding some adaptations to the heart and muscles.
3) Combining exercise and passive heating
Given that both passive heating and exercise can have health benefits, it is possible that combining the strategies could result in even greater benefits. Indeed, one study has shown people who regularly engage in sauna-bathing and have high fitness levels, have a reduced risk of death by cardiovascular disease compared to individuals with either high fitness levels or engage in sauna-bathing alone.
Take home message: Passive heating, such as regular hot baths, can improve your health. Whilst it should not replace exercise, passive heating may be a good strategy to get health benefits for people who don’t exercise and may even be a good addition for those that do!