Fans of Bikram Yoga know that it’s not really Bikram unless the room is hot: 104-105 degrees Fahrenheit, with a humidity of 40 percent. But a new study sponsored by the American Council on Exercise found that practicing yoga in such a warm environment can lead to potentially dangerous core body temperatures of 103 degrees and higher.
Researchers at the University of Wisconsin had 20 regular Bikram practitioners swallow core body temperature sensors prior to performing the standard 26 poses for 90 minutes in a room with 105° F heat and 40 percent humidity. One male in the study had a body temperature of 104.1 °F by the end of the class, and seven of the subjects had body temperatures greater than 103° F. This concerned researchers, because 104 is the temperature at which some people will start to display some of the early signs of heat intolerance, says Dr. Cedric Bryant, Chief Science Officer of the American Council on Exercise.
However, Dr. Bryant emphasizes that despite the elevated core temperatures, none of the subjects in this study displayed signs of heat intolerance (a precursor to heat illness and heat exhaustion), which is a good thing.
“If you adhere to common-sense guidelines, most presumably healthy individuals can have very safe experiences practicing Bikram Yoga,” he says, adding that Bikram offers a number of health benefits from improved flexibility to relaxation and should not be discouraged.
Watch out for these symptoms of heat exhaustion
Certified Bikram instructors are pretty well-versed in observing signs of heat intolerance, Dr. Bryant notes. But he urges participants, especially those who are new to Bikram, know and be on the lookout for the signs and symptoms, including mild nausea, dizziness, headache, unsteadiness, and mild cramps.
“Allow acclimation to occur. During the first few sessions, pay close attention to your body. The signs of heat intolerance are clues that you’re not tolerating the heat and may need to take a break and get to a cool location,” he says. He also cautions participants to make sure they are well-hydrated, drinking fluids before and throughout class and rehydrating after class (sports drinks with electrolytes may be a better choice than water for many participants due to the 90-minute length of the class, he adds).
Find a studio with an air-purge circulation system
Jennifer Lobo, co-owner of Bikram Yoga NYC, says she was “very surprised” by the study’s findings, since she has never had a serious heat-related issue in one of her classes since she opened her studio in 1999.
While sweating is the body’s main defense against overheating, Lobo says her studio’s purge system (which pulls out stale air from the studio and pulls in fresh air from outside) helps circulate air and reduce the humidity in the room. Teachers are also asked to read the faces of the students to look for problems and adjust the heat accordingly. "If they’re getting really red or white, or if more than three people are sitting down in a busy class, [the teachers will] adjust the heat and let in more air,” she says.
Hydrate, and don't overdo it
Lobo also encourages students to drink water and take electrolytes before and during class, which are always on the podium where the teacher stands. “If anyone is sitting down, light-headed, or nauseous, we always give them electrolytes.”
More than anything else, the heat is a tool to warm up the body to avoid injury and enhance flexibility, Lobo says. “Ultimately, it’s more about the asanas and the postures than the heat,” she explains, noting that the 26 Hatha Yoga postures and two Pranayama breathing techniques are designed to work every muscle, tendon, ligament, joint, and internal organ in the body.
Consider alternatives if you're pregnant
Dr. Bryant recommends that pregnant women, individuals with known cardiovascular disease and diabetes consider practicing yoga in a thermally neutral environment (though Lobo says pregnant women regularly take their temperatures in her classes, and no one has recorded a temp over 99). But for the general population, he thinks Bikram has a lot to offer. “Just make sure you take some basic, straightforward, common-sense precautions for the safest possible experience,” he says.