Nothing beats the delightful feeling you get when a workout is over, except maybe a hot bath! You might think that the two have little in common. With a workout, you’re actively contracting your muscles and working up a sweat. With a hot soak in a tub, you might sweat a bit from the heat of the bath, but you aren’t actively moving. In fact, most people take a bath to relax and unwind, not to increase their heart rate or derive cardiovascular benefits. But recent research suggests the two may have some things in common, and both may be beneficial for your health.
Not All Stress is Bad Stress
We know that any type of stress you place on your body causes it to adapt and become more resilient. The key is the stress you place on your body should be short-term and controlled. Longer term, stress has detrimental effects on the body as it overwhelms the body’s adaptive capabilities. Exercise, in moderation, is one type of stress that triggers positive adaptations and, it too, is a form of stress. You know this because you feel your heart beating faster and you become tired or winded. No wonder! Exercise activates fight or flight hormones that are released during periods of stress. These hormones increase your heart rate, blood pressure, breathing rate, and increase blood flow to your muscles, all in preparation for movement so you can fight or run!
Exercise also transiently elevates inflammatory markers, including an inflammatory marker called IL-6. That might sound like a bad thing, but the transient inflammation that exercise sparks leads to an adaptive response that’s anti-inflammatory in nature. In other words, short-term, strenuous exercise ramps up the body’s anti-oxidant and anti-inflammatory defenses. So, longer term, exercise actually has an anti-inflammatory effect on the body.
Based on a study, that’s true of a hot bath too. In a study, researchers asked healthy, but overweight and sedentary, men to immerse themselves in hot water, similar to a hot bath. On a different occasion, three days later, they sat in a room at ambient room temperature to serve as a control. During the hot water bath phase, the men soaked for an hour in 102-degree F. water. After soaking, the researchers collected blood samples and monitored the subjects’ vital signs. They continued to take blood samples to check levels of inflammatory markers for several weeks.
What they found were the men who sat in the bath experienced an elevation in IL-6, a marker of inflammation. But, when they measured inflammatory markers two weeks after the hot baths, the markers were lower than before. Although the hot bath transiently boosted markers of inflammation, soaking in the tub was linked with a reduction in inflammation afterward.
Another interesting observation: Sitting in the hot bath was tied to a boost in the production of nitric oxide, a gas produced by the inner walls of arteries. Nitric oxide opens up the wall of arteries and decreases the resistance to blood flow. Increased nitric oxide also helps to lower blood pressure. What’s more, the men who sat in a hot bath experienced a reduction in fasting insulin and blood sugar, both positives for metabolic health and for cardiovascular risk.
Another study carried out by researchers at Loughborough University found that soaking in hot bath water lowered blood sugar levels more than an hour of cycling. A 60-minute soak in the tub, at a temperature of 104 degrees F, also burned an additional 126 calories due to an increase in resting metabolic rate. So, taking a hot bath may lower blood sugar and boost resting metabolism. It’s not clear whether taking a hot bath regularly helps with weight loss. More research is needed. It’s possible that people eat more after a hot bath, compensating for the additional calorie burn.
Sauna Bathing Has Health Benefits Too
Research shows that sitting in a sauna has similar health benefits. According to research, sauna bathing boosts blood vessel function by increasing nitric oxide and is linked with a reduction in blood pressure. In fact, a study of 2,300 Finish men that followed the participants over 20 years found that those who regularly sat in a sauna were less likely to die of a cardiovascular event over the course of the study. The more often the men sauna bathed, the lower their risk of dying.
It may be that sauna bathing or a hot bath places just enough stress on the body to bring about a protective response. In response, the body adapts and becomes stronger and more resilient. Not everyone has access to a sauna, but almost anyone can soak in a hot bathtub. One downside is the temperature of the bath water was high enough to be uncomfortable, especially after an hour of soaking. Also, a hot bath may not be appropriate for people with certain health issues.
Hot Baths and Saunas Shouldn’t Replace Exercise?
Although preliminary studies are encouraging, baths and saunas aren’t a replacement for exercise. You need resistance training to prevent loss of muscle strength and size as you age. Sitting in a hot bath or sauna does nothing to prevent muscle loss or keep you strong and functional. Where it’s beneficial is as a compliment to exercise. Take a hot bath or chill out in a sauna after a tough workout. For people who can’t exercise, a hot bath or sauna might help them achieve some of the health benefits that aerobic exercise offers, such as a reduction in blood sugar and blood pressure lowering.
The Bottom Line
A hot bath is not a replacement for a workout but taking one may have heart health benefits and modestly help with blood sugar control. It’s a good stress reliever too!
Journal of Applied Physiology, 2018; DOI: 10.1152/japplphysiol.00407.2018
Journal of the American College of Cardiology. Volume 45, Issue 10, 17 May 2005, Pages 1563-1569.
Science Daily. “Frequent Sauna Bathing Keeps Blood Pressure in Check”
American Journal of Hypertension, Volume 30, Issue 11, 1 November 2017, Pages 1120–1125.
The Telegraph. News. Science. “Hot bath beats cycling for lowering blood sugar levels for type 2 diabetics”