Is hot yoga beneficial for you?
The heat can be very good — but also risky
Adapted from a story by Emily Sohn for The Washington Post.
More than 36 million Americans practice yoga, according to a 2016 survey. And although there are no firm statistics on how many do their poses in heated spaces, anecdotal evidence suggests that hot yoga has grown in popularity since it was introduced to the United States in the 1970s.
So researchers like Brian Tracy and Mace Firebaugh decided to study it.
Health claims of hot yoga
Franchises that offer hot yoga say its benefits include strengthening the heart, cleaning out the veins, cleansing impurities from the body and regulating metabolism and the immune system, and they often suggest that those benefits are greater than from unheated yoga.
Results from Tracy’s study
Tracy and his graduate student decided to do a study of hot yoga.
Published in 2008, the study randomly assigned 21 healthy young adults to attend three Bikram classes a week for eight weeks or to do whatever activities they normally did. Overall, most participants were only minimally active before the study, and none had a history of yoga practice. After two months, the yoga group showed improvements in flexibility, leg strength and the ability to balance on one leg, with the biggest gains in people who had been most unsteady and least flexible at the beginning.
Since then, according to a 2015 review by Australian researchers, a few studies of healthy young adults have suggested that hot yoga may be good for the heart. That review turned up evidence that arterial stiffness decreased in one small group of young adults and that insulin resistance declined among a small group of older participants who did Bikram yoga. In a 2011 study of 51 adults, people reported less stress after doing Bikram classes for eight weeks.
Results from Firebaugh’s study
Among 700 people whom Firebaugh has surveyed in an ongoing study:
- 48 percent say that hot yoga improves their mood.
- 47 percent report better flexibility.
- 34 percent feel less anxiety.
- 33 percent report clearer skin.
- Some have reported negative effects such as nausea, dizziness and dehydration, but those symptoms are usually mild.
Does it burn calories?
The survey found another intriguing result: 43 percent of participants reported losing weight as a result of doing hot yoga, but that linkage might be a coincidence. Studies have yet to connect hot yoga with weight loss, the 2015 review found. And as sweaty as a hot-yoga session can be, it may not burn as many calories as people think.
In a 2014 study of 19 experienced Bikram practitioners during a single 90-minute session, Tracy and colleagues found that men burned an average of about 460 calories and women burned about 330. It’s about the same number of calories you’d burn during a brisk walk for the same amount of time, Tracy says. And even though that’s about 50 percent more than what people burn in a typical yoga class, it was much less than what people thought they had burned. (Heart rates peaked above 150 beats per minute during the toughest parts of class — a sign more of the body’s response to heat than of a boost in calorie-burning.)
Even as research begins to point to some potential pluses of hot yoga, it’s not clear whether heat has anything to do with those benefits. Studies on other types of yoga have shown good outcomes, too, including improvements in heart health, range of motion and balance.
Heat’s effects on the body, meanwhile, are complicated. Exercising in the heat carries risks, including heatstroke and dehydration. But emerging evidence, including a long-term study published last year by Finnish researchers, suggests that regular sauna use can lower blood pressure and reduce the risk of heart disease. A 2016 review found that raising body temperature might ease symptoms of depression. And applying heat directly to muscles can increase range of motion.
Risks and concerns
And a 2015 study reported that people’s core temperatures during Bikram classes could rise above 104 degrees. But that research was flawed, says Tracy, whose 2014 study showed a maximum core temperate of 101.6, with an average rise to 100.3. The danger zone, he says, begins at 102 degrees.
Women who are pregnant and people with preexisting conditions — such as cardiovascular disease, back pain, asthma and diabetes — should consult a doctor before beginning a hot-yoga practice, adds Mace Firebaugh. Her own low blood pressure, she suspects, explains why hot yoga doesn’t suit her.
“In general, hot yoga is likely safe, and the risks are minimal and mild,” Mace Firebaugh says. “If you love it, do it. If it doesn’t work for you, there’s probably going to be another type of yoga that is going to be fine. Hot yoga might not be for everybody.”
