Study turns up the heat on hot yoga classes
Popularity of hot yoga classes grows, but overall physical challenge comes into question
Catherine Pamel was hooked the first time she stepped into a hot yoga studio five years ago. A veteran yogi, her practice had been limited to classes held at room temperature. But from her first series of sun salutations performed in 38 C heat, Pamel knew she had found her happy place.
“I love the intensity,” she said. “And I love the sweat.”
Pamel is one of the many Canadians who have jumped on the hot yoga bandwagon. Some revel in the heat. And some, like Pamel, like the intensity of the workout.
But is hot yoga more physically challenging than the same class performed in a more temperate studio? A team of researchers from Central Michigan University set out to find the answer, recruiting 14 people with a range of yoga experience.
“The aim of the study was to determine whether yoga exercise performed in a hot environment would elicit greater objective and subjective measures of exercise intensity and energy expenditure than yoga performed in a thermo-neutral environment,” said the researchers.
Outfitted with heart rate monitors, the study subjects (seven men and seven women) performed two identical 20-minute yoga classes led by the same instructor, at the same time of day, one week apart. The hot practice was performed at a tropical 35 C, the cooler version at 22 C.
During both classes, oxygen consumption and carbon dioxide production were monitored to determine the intensity of the workout and the subjects were quizzed every five minutes regarding their perceived level of exertion.
All the study subjects reported hot yoga felt more physically demanding than the same workout performed in cooler temperatures. Heart rate monitor readings backed up their claims, with heart rate significantly higher during the hot yoga class. But when it came to measuring energy expenditure, there was little difference in intensity between yoga workouts done in a hot room and the same practice performed in a cooler environment.
“Our findings indicate that identical yoga sessions performed in a thermo-neutral and hot environment result in similar energy expenditure,” the researchers said.
It’s not unusual for heart rate to increase during workouts performed in the heat, which indicates the extra effort it takes to cool the body. Add that to the environmental challenge of exercising in a 35 C room, and it’s no wonder hot yoga gives off a more extreme vibe than yoga performed in an environment 13 degrees cooler.
Yet it’s that elevated heart rate that can lead to confusion when it comes to determining the amount of energy expended during a hot yoga class — especially among those who wear an activity/fitness tracker. Most activity trackers use built-in heart rate sensors to determine calorie burn, using the premise that as heart rate increases so, too, does the amount of energy expended.
Based on the findings of the Central Michigan study, however, there’s a mismatch between heart rate and energy expenditure during hot yoga, meaning it’s likely your activity/fitness tracker has overestimated the number of calories burned.
But that’s not the only discovery worth noting. The researchers also reported an increased reliance on carbohydrates for energy during hot yoga, which, like an elevated heart rate, isn’t unusual when exercising in a hot environment. A word to the wise, however, for athletes using hot yoga to relax after a tough workout: This added drain on carbohydrate stores (muscle glycogen) can inhibit the muscles’ ability to recover. So you might want to reconsider taking a hot yoga class the day after running a marathon or a tough gym workout — especially if you’re expected to exercise again the next day.
Lisa Marcoux, who attends a hot yoga class daily, has no plans to abandon her favourite form of exercise, despite the suggestion that its intensity might be overstated. She feels the heat makes it easier for her to boost the intensity of her yoga practice. Her muscles feel more pliable and the transition from pose to pose smoother.
It’s likely most hot yoga enthusiasts feel the same way, which might be reason enough to turn up the temperature on their practice. But for those who believe that hot yoga is a shortcut to getting fitter and leaner, the latest research suggests otherwise.
“Mainstream markers of exercise intensity, including perceived exertion and heart-rate response, would suggest to yoga patrons that they are working harder during hot versus thermo-neutral yoga,” the researchers said.
“Unfortunately, this may lead them to believe they are exercising more vigorously and expending more calories than they actually are.”
Of course, Marcoux suggested another reason so many Canadians prefer their yoga on the warm side: “In the cold winter, it feels great.”