Hot yoga -- and hot barre and hot spinning classes -- is a booming trend, with yogis crowding into sweltering rooms to twist their bodies to the point of exhaustion. But whether or not yoga in heated rooms, sometimes up to 105 degrees F (40.5 degrees C), is safe has been a point of contention. Now a new, small study suggests it's perfectly safe for healthy adults, as long as it's not too hot.
According to the study from the American Council on Exercise, as long as you stay hydrated, hot yoga is just as safe as yoga in more moderate temperatures, Prevention magazine reports.
University of Wisconsin-La Crosse researchers recruited 20 healthy adults between the ages of 19 and 44. Researchers measured the core body temperature of the subjects both after a 60-minute Vinyasa yoga class in a room set to 70 degrees F (21 degrees C) and after a 60-minute hot yoga class heated to between 90 and 95 degrees F (around 32-35 degrees C) with 35 to 40 percent humidity.
After both classes, the students' core temperature rose to an average of 99 degrees F (37.2 degrees C), which is well below the unsafe threshold of 104 degrees F (40 degrees C), study author Dr. John Porcari told Prevention.
"When you're exercising it's almost like your body shuts down if you get to that level," he said in the report. "It's considered dangerous, and heat-related illness is almost impending."
However, if you're not hydrated, this could cause problems. He suggests drinking plenty of water, including drinking 6-8 oz or 177-236 mL of water immediately before class and more during class as needed.
Also, if you're new to hot yoga, keep in mind that it can take anywhere from 10 days to two weeks for most people to fully acclimate to exercising in the heat, so be sure to give yourself time to adjust, he noted.
Still, more tests need to be done to gauge the safety of Bikram yoga, which involves 90 minutes in a room heated to around 105 degrees F (40.5 degrees C).
Fabio Comana, an exercise physiologist with the American Council on Exercise (ACE), told MSNBC that the body wasn't designed to perform yoga in extreme heat (over 104 degrees F/40 degrees Celsius) and that doing so can damage proteins.
"You may think it's purifying and cleansing but you have to respect the physiology of the body," he said.