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When you’re hot, you’re hot… but that might not be the adage everyone would like to adopt when it comes to yoga.

Bikram yoga, commonly known as “hot yoga,” continues to draw ardent supporters as well as harsh critics.

This style of practicing yoga in a heated room is still popular with a slice of yoga enthusiasts despite a scandal that apparently prompted the creator of this form of yoga to leave the United States (more on that later).

Overall, yoga continues to grow in popularity in the United States.

A 2016 survey estimated that 36 million Americans practice some form of yoga. That was up from 20 million in 2012.

Women make up 72 percent of yoga participants, and people between the ages of 30 and 49 make up 43 percent of practitioners.

There aren’t any firm numbers on how many of these people practice hot yoga, but those that do say they enjoy sweating it out.

A Bikram yoga class moves through a fixed series of traditional poses in a 90-minute session, in a room with an air temperature of 105 degrees and 40 percent humidity. Many studios tinker with the formula in order to offer their own versions of hot yoga.

However, you won’t find such a setting at Yoga Shala in Portland, Oregon.

Director Jody Kurilla happily sends would-be hot yoga students “down the street” to another studio.

For the 25-year yoga devotee, “hot yoga” is a contradiction in terms. Classic yoga should be practiced without profuse sweating or an elevated heart rate, she told Healthline in 2015.

And the practice is not about extremes. It’s about listening to your body without distractions, she said.

“The idea is if you’re sweating a lot, the session is too difficult. You can be lightly sweating, but if your [breathing] or your heart rate starts to go up, you’re supposed to take a break. So to put yourself into a hot room, and do that on purpose, it’s not what yoga was designed to do,” she said. “You’re supposed to be cultivating prana, or energy, not dispersing it.”

She says hot yoga practitioners get addicted to the endorphins their bodies produce in response to being pushed further than they want to go.

“Yoga is not about extremes,” Kurilla said. “As the Dalai Lama said, the highs are very high, the lows are very low, and the middle is very boring. But after time, it becomes much more profound.”

Hot yoga proponents told the Washington Post late last year that doing the exercise in a heated room strengthens the heart, clears out the veins, cleanses impurities from the body, and boosts the immune system.

The heat forces the heart to beat faster, which advocates say provides a better cardiovascular workout and burns more calories.

They also make the point that yoga comes from India, where the climate is warm.

But Kurilla fires back, “They don’t practice outside in the hot weather. They practice in the morning before the sun comes up and in the evening after the sun goes down.”

Yoga in a heated room is a novel, contentious experiment in the 5,000-year history of yoga.

There’s a thick bundle of modern scientific studies documenting the potential for conventional yoga to lower stress and blood pressure and improve flexibility and balance.

But little is known about what happens when you move yoga into a super-heated room.

Throwing cold water on hot yoga

The American Council on Exercise (ACE) published a study in 2015 raising concerns about Bikram yoga.

During a 90-minute class, body temperature rose consistently in healthy participants experienced in hot yoga, the study found. The participants’ temperatures topped out at 103 degrees, narrowly missing the 104-degree threshold that doctors consider dangerous.

“For a person who’s unfit or not used to Bikram, there’s some [concern] that they might experience some level of heat intolerance,” said Cedric Bryant, PhD, chief science officer at ACE.

ACE recommends that newcomers stick to conventional yoga or try hot yoga at a studio that offers it at lower heat. An earlier ACE study found that hot yoga classes at lower temperatures do not pose a risk. But all hot yoga participants should lie down or leave the room if they feel nauseous, light-headed, or confused in a class.

“You do want to use some common sense if you’re feeling out of sorts,” Bryant said.

Allison Abel Rissel, a North Dakota yoga instructor who, as part of her graduate training in exercise physiology, published research on the health benefits of hot yoga, agreed.

“It is hot in that room, but as long as you’re properly hydrated, I think it’s a manageable heat,” she told Healthline in 2015.

But, according to Mindy Caplan, a yoga instructor and a health fitness specialist certified through the American College of Sports Medicine, many participants don’t ease in to the higher temperatures.

“Groupon’s out there saying you can try hot yoga, and it’s usually somebody that’s never practiced yoga before and they go in there,” she told Healthline in 2015. “They’re not well hydrated. They’re not in shape.”

Caplan briefly tried Bikram and doesn’t recommend it for students.

Pregnant women and people with diabetes or any sort of cardiovascular problem, including high blood pressure, should avoid hot yoga, according to recommendations from ACE and Canadian health groups.

Rissel said she’s seen pregnant women in hot yoga classes, but they were acclimated because “they’d been doing it for years.”

Culture shock

Part of what sets Bikram apart even from other forms of hot yoga is the style of instruction, critics say.

While most yoga classes, including many hot ones, encourage students to take things at their own pace, Bikram instructors often don’t.

Critics say teachers trained at the Bikram Yoga College follow a script, and the script calls for them to encourage students to stretch further into their poses and to not leave the room if they feel overwhelmed by the heat. Instructors sometimes follow students out of the room to persuade them to come back in.

Some liken the instructional style to boot camp.

But Rissel defended the instructors’ efforts to keep students in the yoga studio. The rationale is “mindfulness,” she said, or encouraging students to simply accept their feelings rather than escape them. Mindfulness can be effective at helping people handle psychological stresses.

But the persistent urgings of Bikram instructors make it difficult for some people to listen to their own bodies, Caplan said.

It’s hard to recognize your limits, she said, “when you’re pretty much being told, ‘This is how you do it: Go deeper, go deeper!’”

You won’t melt your waistline

Still, Bikram yoga isn’t as dangerous as, say, an early-season football practice in Texas, Bryant said.

“The fact of the matter is that there are large numbers of participants in Bikram, and it isn’t like the vast majority of those people are having any issues,” Bryant said.

Hot yoga’s saving grace, he said, is that it’s not all that vigorous. The body can handle gentle activity at a high temperature, but vigorous activity, such as football, is too much.

Yet, the caloric tally of hot yoga is one of its major selling points. It’s one reason why hot yoga is Rissel’s primary form of exercise, she said.

This selling point appears to be unfounded.

According to a series of studies, including one funded by the Bikram Yoga College, hot yoga burns only about 500 calories in a 90-minute class — half of what some proponents and fitness apps promise.

“I wouldn’t advocate it as a practice to try to promote greater calorie burn for weight loss,” Bryant said. “I think most practitioners would be sorely disappointed if they went to it for that.”

In fact, a small study published early this year concluded it’s the poses and stretching involved in Bikram yoga that benefit the participant… not the heated room.

Stretching boundaries

Other students brave the smell of hot yoga’s sweat-soaked rooms because they feel more flexible in the heat.

But the jury is still out on whether this flexibility is a good thing or an invitation to injury.

Critics like Caplan and Kurilla say that, with instructors urging students to push further, the environment is ripe for injury. Caplan injured herself doing Bikram yoga.

“People don’t listen to their bodies, and they injure themselves because they overstretch. I practiced [Bikram yoga] for probably three months until I injured myself — and I don’t often do that, and I know that it was because I overstretched,” she said.

Hot yoga devotee Rissel agreed the heat increases flexibility. But she sees overstretching as simply a question of overdoing it.

“If you’re going to overstretch in a Bikram class, you’re going to overstretch in any class,” she said.

Injuries occur in all forms of yoga, but they’re usually mild. Still, it seems that if there were a rash of injuries at hot yoga studios, the word would get out, as Bryant says.

In the final tally, there is an additional risk from the heat in super-hot yoga, and there is no evidence of benefits in hot yoga that don’t exist in conventional yoga, according to Karen Sherman, PhD, MPH, a researcher on alternative approaches to health at Group Health Research Institute.

“I do not recommend that people seeking yoga for health use hot yoga,” Sherman told Healthline in 2015.

Bryant said ACE’s findings are in line with Sherman’s analysis, but ACE stopped short of advising healthy people to avoid hot yoga.

Why?

“There are just some people who like exercising in that heated environment,” he said.

Even Kurilla would agree with that.

“If people get out there and they’re moving and they feel better, that’s great. If they get out there and they damage themselves, then that’s a problem,” she said. “People come to yoga for whatever reason they come to the practice, and they either find it and they stay with it or they’re on to the next thing.”

The scandal that shook up Bikram

The Bikram empire used to oversee 650 studios worldwide.

However, many of those studios, especially those in the United States, have closed in the past three years.

The company used to be headquartered in Los Angeles, but that office was reportedly shut down in 2016 when Indian-American yogi Bikram Choudhury, the creator of “hot yoga” in the 1970s, moved to India after losing a $7 million sexual harassment lawsuit.

The suit was one of at least six civil actions against Choudhury filed in the past few years, alleging assault or rape.

The Bikram studios that remain open are run by Choudhury’s former attorney, who was granted control of the company by the courts.

Some of the studios, such as Rise Hot Yoga in Los Angeles, don’t use Bikram in their name, although the title remains on some of their classes.

At one point, it was mandatory that instructors be trained by the Bikram College of India.

That teacher training is now held outside the United States. The sessions offered last fall and this spring were held in Acapulco, Mexico.

Editor’s note: This story was originally posted on May 15, 2015 and was updated by David Mills on June 15, 2018.