From yoga to boot camp to the barre, heated exercise is heating up. With your heart thumping and body dripping, surely you’re racking up more benefits than you’d get exercising in a cooler room, right? According to the latest research, the answer is yes … and no.
Let’s start with calorie burn. Real talk: Heat doesn’t help. “The amount of calories you burn is directly related to the actual movements you do,” says Craig Crandall, Ph.D., professor of internal medicine at the University of Texas Southwestern Medical Center. “If the movements are the same, you won’t burn more calories just by doing them in the heat.”
Take Bikram yoga, possibly the most popular heated exercise. The 105-degree heat and 40 percent humidity are believed to help you increase strength and flexibility and boost weight loss—some fans swear they burn up to 1,000 calories in one session. But science doesn’t entirely back this up. While Colorado State University researchers found that Bikram practice can improve balance, strength and flexibility, it’s not the calorie-torcher people think it is. In the CSU study, women burned about 330 calories in a 90-minute class. That’s on par with a 90-minute vinyasa session sans heat, or a brisk walk of the same duration.
In fact, warm workouts only feel tougher. “Heart rate is often higher in the heat, so it seems like you’re working harder, but the heart is simply pumping more blood to your skin to help dissipate heat,” Crandall says. And your ticker might not even reach higher rates: A small American Council on Exercise study found no heart rate difference between yogis in a heated class and those in a regular class.
So what are the rewards of sweatier sessions? Cranking up the thermostat can help you limber up quickly. “We warm up to increase body temperature and boost blood flow, so muscles are less susceptible to injury,” says John Porcari, Ph.D., executive director of the La Crosse Exercise and Health Program at the University of Wisconsin-La Crosse. “In the heat, this process occurs within just a couple of minutes.” Mimi Benz, owner of The Sweat Shoppe, a heated spinning studio in North Hollywood, says that warm-ups during her classes are shorter than in a typical spinning class. “We get straight to the point,” she says.
Another benefit of heating up your workouts: increased flexibility and range of motion, which actually means a smaller risk for injury than if your muscles were cold, despite what you might have heard about overstretching, Porcari says. “Pulling a muscle is excruciating, so even in hot yoga, you’d feel pain and back off way before getting to that point.”
Ultimately, the biggest boost sweat seekers reap is in their heads. And the mind matters: “Anything that encourages you to exercise is a good thing, even if you’re not working harder or burning more calories,” says Sam Altstein, D.O., medical director of the Beth Israel Medical Group in New York City. As Benz puts it, “You feel like more of a badass when you’re dripping sweat at the end of a hard workout—it’s what keeps people coming back.”