Heat therapy is hot right now. Saunas are popping up in more backyards and fitness centers. And heat is part of the constant conversation around optimizing health and wellness.
But the idea of leveraging heat for better health is not new, according to University of Oregon human physiologist Christopher Minson. And it's certainly not just another internet fad, as heat therapy is grounded in science and offers many evidence-based benefits.
Some of those benefits include increased fitness, immune activity, cardiovascular and metabolic health, and blood sugar regulation. Heat has also been linked to a lower risk of Alzheimer's disease and major depressive disorder, and early evidence suggests it may reduce dementia risk and provide additional mental health benefits.
Researchers have even found that heat can help people live longer, said Minson, Kenneth and Kenda Singer Professor in Human Physiology and co-director of the Exercise and Environmental Physiology Labs.
In a recent review paper, Minson rounded up the science behind heat therapy and how it can be most effectively harnessed to benefit health and fitness.
His takeaway: It's not a miracle cure, but spending regular time in a hot tub or sauna is something relatively simple (and enjoyable) that people can do to benefit their health.
How has heat shaped human evolution?
Even without stepping into a sauna or hot tub, the human body has adapted to heat.
Humans have less body hair than most other mammals but retain hair on the head for protection from direct sun exposure. Humans are also highly efficient at sweating and excel at running in the heat - traits likely tied to early humans' need to hunt on sweltering savannas.
At the same time, modern life offers many ways to avoid heat, including air conditioning and climate-controlled environments.
While those advances are important, especially on a warming planet, people may have become too comfortable, Minson suggests. It could serve us to sometimes turn up the heat more so we can better reap its many health benefits.
"In order to exploit our ability to adapt to the heat and get benefits from it, we have to get hot," Minson said. "There's so much convincing evidence that heat is healthy and so many reasons we should regularly heat our bodies up."
What is the science behind heat therapy?
One of the reasons heat offers so many health and fitness benefits is because it mimics the physiological effects of exercise.
During exercise, body temperature rises and muscles experience microdamage that is repaired during recovery, making them stronger. This stress-recovery-adaptation cycle is key to improving fitness.
Similarly, sitting in a sauna or hot tub raises body temperature, increases heart rate and boosts blood circulation. Heat therapy stresses out the body and then it adapts, just like it's done for hundreds of thousands of years.
"Through both exercise and heat, stress adaptation is aligned with better health," Minson said.
Who can benefit from heat therapy?
Nearly everyone can benefit from heat therapy. However, people with certain conditions - including pregnancy, multiple sclerosis, muscular dystrophy and heart failure - need to exercise caution.
Heat can be especially useful for people who cannot fully exercise, like individuals with spinal cord injuries.
It can also provide performance-enhancing benefits for elite athletes. Minson works with Olympians and professional athletes to incorporate heat into their training, helping them compete in hot environments and increase red blood cell production, which improves oxygen delivery to muscles.
Heat essentially offers the same performance boost that an athlete gets from living at a high altitude, he said.
How can people best use heat therapy?
Saunas and hot tubs are some of the most effective and dependable sources of heat because they're controlled environments without temperature fluctuations. Other options include steam rooms, bathtubs, heated yoga studios, or even spending time outdoors on a hot day.
Minson uses a scale from 0 to 10 to gauge heat exposure. Zero is comfortable while 10 is dangerously hot. A target range of 6 or 7, hot but tolerable, is ideal.
People should aim for sweat-inducing sessions lasting 10 to 20 minutes, building up to 20 to 30 minutes per session, research suggests. Breaks to cool down are fine.
Large population studies in Finland have found that regular sauna use is associated with lower rates of cardiovascular disease and longer lifespans. In these studies, participants used saunas for 20 minutes at a time, and researchers found that more frequent use produced greater health benefits.
"What data has shown, and what's supported by my understanding of physiology, is that you want to have regular exposure," Minson said. The ideal frequency for heat therapy is three to five times per week, but even one session per week can be beneficial.
What are the limitations of heat therapy?
While there's plenty of evidence to support the health and wellness benefits associated with heat therapy, it's not a replacement for exercise.
"You're going to get more benefits from exercise, that's the bottom line," he said. "Exercise leads to increased strength, greater bone density and other fitness gains you won't get from heat therapy."
But for people limited by injury or health conditions, heat therapy can offer a safe way to improve fitness.
Plus, health perks or not, a cozy sauna session or hot tub dip on a chilly day just feels good.
