ACE® Study Focuses on Safety of Bikram Yoga by Measuring Heart Rate and Core Temperatures During Class

Posted: Apr 22, 2015 in

Researchers Say Many Participants’ Core Body Temperatures Reached Very High Levels During 90-Minute Session

SAN DIEGO, April 22, 2015—In a new independent study commissioned by the American Council on Exercise (ACE), researchers found that a large number of the participants reached a very high core temperature of greater than 103 degrees F during a Bikram yoga class. Notably, well-established sports medicine guidelines state that exertion-related heat illnesses can occur at a core temperature of 104 degrees F.

A typical Bikram yoga session lasts 90 minutes and consists of 26 poses and two breathing exercises performed in a room heated to 105 degrees F with 40 percent humidity. Many Bikram yoga practitioners say that having the mental strength and focus to overcome this challenge is a big part of the draw. Many advocates of Bikram claim improved mindfulness, flexibility, strength, muscle tone and general fitness as a direct result of the practice.

But, according to ACE, though there are several benefits to practicing Bikram yoga, the concerns associated with the potential for heat-related challenges among some participants appear warranted.

ACE Chief Science Officer Cedric X. Bryant, Ph.D., FACSM, noted, “Exercising in hot and humid environments—whether inside a studio while practicing Bikram yoga or running outside during the warm months of summer—can place participants at risk for heat-related illness, especially if individuals do not adequately hydrate before, during, and after exercise.” Bryant added, “It’s essential that instructors of Bikram yoga are educated on how to recognize the signs of heat intolerance and respond appropriately in the event that a heat-related illness occurs.”

Conducted by researchers at the department of exercise and sport science in the University of Wisconsin, La Crosse, the study tested 20 (7 male and 13 female) apparently healthy volunteers ranging in age from 28 to 67. All subjects regularly practiced Bikram yoga. Each participant swallowed a core body temperature sensor and wore a heart-rate monitor throughout a class led by a certified instructor. Core temperature was recorded prior to the start and every 10 minutes during the session. Researchers also recorded heart rate every minute during the class, and ratings of perceived exertion at the end of class using a 1 to 10 scale.

Results showed the average heart rate for men was 80 percent of the predicted maximum and 72 percent for women. The highest heart rate achieved during the class for men was 92 percent of the predicted maximum, while 85 percent for women. The average highest core temperature was 103.2 degrees F for men and 102.0 degrees F for women. One male in the study had a core temperature of 104.1 degrees F by the end of the 90-minute class, and seven of the 20 subjects had core temperatures greater than 103 degrees F. While none of the subjects in the study exhibited signs or symptoms of heat intolerance, core temperatures such as these can pose a certain level of risk for some participants.

“Given the popularity of Bikram yoga and its proven benefits, it is likely here to stay,” Bryant said. “It’s up to the instructors to make sure it is done safely and efficiently by adapting participants gradually to the hot and humid environment, and encourage them to drink fluids before, throughout, and after the class.”

For more information, visit:

About ACE

The nonprofit American Council on Exercise (ACE) educates, certifies, and represents more than 55,000 fitness professionals, health coaches, and other allied health professionals. ACE advocates for a new intersection of fitness and health care, bringing the highly qualified professionals that ACE represents into the healthcare continuum so they can contribute to the national solution to physical inactivity and obesity. ACE is the largest certifier in its space; all four of its primary certification programs are accredited by the National Commission for Certifying Agencies (NCCA), the gold standard in the United States for assessing professional competence. ACE also plays an important public-service role, conducting research and making available science-based information, and resources on safe and effective physical activity and sustainable behavior change. For more information, call (800) 825-3636 or visit AMERICAN COUNCIL ON EXERCISE, ACE and ACE logos are Registered Trademarks of the American Council on Exercise.


More ACE Press Releases