The Lukewarm Truth About Hot Yoga
A recent study on the (literally) hot fitness craze reveals surprising findings.
Article By: Mary Elizabeth Hurn
Lady sweating
Hot yoga is a polarizing topic in the fitness world; people either love it, hate it or are scared to try it. But a recent study by the American Council on Exercise (ACE) shows that it’s not as physically taxing or dangerous as you might think. Which begs the question: Is all that sweating really worth it?
Hot yoga is typically done for 60 minutes in a room with a temperature ranging from 90° to 105°F. (This is not to be confused with Bikram yoga, which is always 90 minutes at 105°F.) The ACE study compared participants’ core temperature, heart rate and self-perceived exertion rate after a 60-minute yoga class in a 70°F room to those same rates after a class in a 92°F room. Here’s what they found:

Rumors of dangerous overheating have been greatly exaggerated. “For those that are presumably healthy, hydrated and listening to their bodies, hot yoga shouldn’t pose undue risk or harm,” says Dr. Cedric X. Bryant, Chief Science Officer for ACE. Average core temperature didn’t increase more in hot yoga than in “regular” yoga. The highest recorded core temperature of any participant was 102.4° — well below the critical zone of 104° in which fatigue and heat-related problems set in. Bryant does urge practitioners to be aware of the symptoms of heat-related illness: headache, cramps, nausea, dizziness or fatigue. “If you experience any of those, remove yourself, get some fluids and cool down,” he suggests.

Doing yoga in a hot room doesn’t necessarily result in a higher heart rate. Heart rate remained the same in both classes. “Looking at heart rate, participants weren't working any harder in the hot yoga class than in the regular yoga class,” says Dr. John P. Porcari, an author of the study and head of the Department of Exercise and Sport Science at University of Wisconsin-La Crosse. “Normally if you go out and walk three miles per hour and then you do it again on a day that’s really hot, your heart rate will be higher. Because the heart rate was identical in this study, this tells me that somehow people must have down-regulated how hard they were pushing themselves in the heated environment.”

But all that sweating makes you think you’re working harder. “There’s a misconception that sweat rate directly correlates with how hard you’re working and how many calories you’re burning,” Bryant explains. “From their point of view, participants were working harder because hot yoga is perceived as more difficult. But the heart rate data made it clear that they weren’t working harder.”

Keep in mind this study did not address calories burned, although Bryant has a strong suspicion that there would be no significant difference in the caloric outputs between the two types of yoga.

Bottom line: If you enjoy hot yoga, keep doing it! But if you’re suffering through an overheated session under the delusion that you’re getting a better workout, consider this your permission to seek a cooler class. Overall, Bryant stresses that all types of exercise serve a purpose. “Don’t get hung up on how many calories you’ve burned. All types of yoga have benefits: increased balance, flexibility and muscular endurance, stress management and, yes, you’ll also burn some calories.”