Research shows a good soak can replicate the effects of cardiovascular exercise without moving a muscle.
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Credit: Getty Images / Willie B. Thomas

People have been soaking in hot springs and other bodies of warm water for centuries, just because it feels good, but only recently has research begun uncovering a number of legitimate health benefits of doing so. The benefits of hot baths are mostly attributed to thermotherapy, sometimes referred to as passive heating, which temporarily raises core body temperature and may positively affect cardiovascular health, glycemic control and chronic low-grade inflammation, according to a mini review published in the Journal of Applied Physiology.

"It's so easy and restful, yet physiologically it conveys a number of the same benefits of going for a run," says Christine Patterson, D.N.P., a functional medicine nurse practitioner and owner of Vital Journey Wellness. "When my patients are tired or depressed and have low motivation to exercise, hot baths are a way to get some of the benefits without the exertion." Regular physical activity is still an important part of a healthy lifestyle, but a hot bath might be a beneficial addition to your routine when your body needs to rest.

A few things to keep in mind: Most scientific studies highlight water temperatures in a range of 100.4 to 105.8°F as therapeutic. Anything much warmer can be risky for the elderly, pregnant women, children and anyone with a preexisting medical condition, so be sure to consult your primary care physician if you fall into one of those categories.

"Most studies that show physiologic benefits have the participants bathing regularly, sometimes daily, often at least 3 to 4 times per week for around 20 minutes or so each time," says Patterson. Showering, she says, has not been shown to confer the same benefits, likely because it fails to raise core body temperature to the same degree.

Bathing regularly can dry skin out, so while you should avoid perfumed bubble baths and products with fragrances and dyes, you may want to consider adding essential oils or Epsom salts. Aside from that, just run some water, lean back and enjoy these surprising benefits of warm baths.

5 Science-Backed Benefits of Hot Baths

1. Warm Water Can Soothe Sore Muscles

Post-workout can be a great time to reap the benefits of hot baths because research shows that the warmth can ease aches and pains. According to one study, indulging in some heat therapy after exercising reduced muscle soreness by up to 47%. In another small study of 60 middle-aged women with fibromyalgia, spending time in a heated pool three times a week for 16 weeks improved their pain and other symptoms.

2. Steeping in a Hot Bath May Boost Your Brainpower

That same study of middle-aged women with fibromyalgia found another interesting benefit of hot baths: In addition to reducing pain, the warm water also appeared to improve cognitive function, possibly because the heat causes blood vessels to dilate and improves blood flow to the brain. Other research has found that middle-aged men who regularly bathed in a sauna had a lower risk of dementia and Alzheimer's disease compared to those who didn't.

3. A Good Soak Could Help Your Heart

Relaxing in a warm tub also relaxes your blood vessels, because the heat causes them to dilate, making it easier for blood to flow through. This temporary decrease in blood pressure is similar to the effects of exercise and may have similar cardiovascular benefits. A 20-year study of more than 30,000 people in Japan—where the benefits of hot baths have been embraced for centuries—found that those who bathed daily (or close to it) were 28% less likely to develop cardiovascular disease and 26% less likely to have a stroke compared with those who took baths less than twice a week, according to a study published in the journal Heart.

4. Hot Baths Could Help Fight Depression

Interestingly, research has shown that the same pathways in the brain that regulate body temperature are involved in depression. There is some evidence that raising core body temperature—say, by soaking in a warm tub—may cause changes in the brain that increase mood-regulating hormones like serotonin. Some research even indicates that, in this regard, the benefits of hot baths may be greater than those of regular exercise.

In a study of 45 people with depression, those who took two 20-minute baths a week (at a temperature of approximately 104°F) had lower ratings on a widely used depression scale compared to those who exercised for 45 to 50 minutes twice a week, according to research published in BMC Psychiatry. Though this is a small study and more research is likely needed to confirm this connection, the findings are still noteworthy.

5. Taking a Hot Bath Before Bed Can Help You Sleep Better

One of the more surprising benefits of hot baths seems to be related to circadian rhythms, which are the biological processes that run according to a 24-hour internal clock and can be influenced by our environment. One of these processes is body temperature. Normally, we cool off by a few degrees as we prepare to sleep. Counterintuitively, taking a hot bath speeds up this process by drawing all your blood to the surface where it can easily be dispersed. So while you may feel toasty warm in the tub, you're actually cooling your core body temperature after you get out, which signals that it's time to snooze.

An analysis of 13 different studies, published in Sleep Medicine Reviews, backs this up, finding that taking a warm bath or shower before bed led people to sleep longer overall and report better sleep quality. According to some of the data, spending as little as 10 minutes in water around 104°F an hour or two before bed decreased the time it took to doze off by nearly 9 minutes.