Posted: Jul 23, 2013 in

Proper hydration and managed temperatures key to ensuring safety


SAN DIEGO, Calif. (July 23, 2013) – Hot yoga is indeed a hot trend with escalated temperatures permeating many yoga studios nationwide. However, the question of safety is often debated as it relates to dehydration, heat exhaustion and muscle damage with room temperatures ranging from 90 to 105 degrees.


In a new independent study commissioned by American Council on Exercise (ACE), researchers found no difference in the increase in core temperature or heart rate between 60-minute regular yoga and hot yoga classes.


“Anytime exercise is conducted in extreme temperatures, it’s important to remain hydrated and to watch signs for overheating,” said ACE Chief Science Officer Dr. Cedric Bryant. “However, this study showed that while higher sweat levels may cause participants to feel like they were working harder, heart rates showed they were actually at comparable levels whether in the regular or hot yoga class.”


Bryant also noted that while the study conducted tested a hot yoga class with an average temperature of 92 degrees, many hot yoga classes including the popular Bikram yoga, are conducted in temperatures of 105 degrees or higher for longer durations and therefore need to be studied further.


Conducted by the University of Wisconsin-La Crosse’s Department of Exercise and Sport Science, the study tested the effects of hot yoga on heart rate and core temperature using 20 healthy, relatively fit males and females ranging in age from 19 to 44.


First, participants swallowed a CorTemp® Ingestible Core Body Temperature Sensor to monitor core temperatures, and then took a 60-minute basic yoga class at room temperature. Each wore a heart-rate monitor during the entire class. Researchers recorded core temperatures five minutes prior to exercise, every five minutes during the class, and five minutes after the session. Heart rate was recorded each minute during the class, while ratings of perceived exertion were recorded at the end.


Within 24 hours, subjects participated in another 60-minute class led by the same instructor that featured an identical series of yoga poses. But this time it was a hot yoga class and the room temperature was approximately 22 degrees higher, about 92 degrees and significantly more humid. Each subject’s core temperature, heart rate and ratings of perceived exertion (RPE) were measured in the same way as in the initial test.

The highest core body temperature recorded for an individual during the hot yoga class was 102.4°F, well below the zone in which fatigue and heat-related problems are imminent, which is at 104°F. What may or may not come as a surprise is that individuals perceived the hot yoga practice to be more challenging than the non-heated class based on RPE despite the fact that physiologically the subjects weren’t working much harder based on their heart rates. During the hot yoga participants averaged 57 percent of maximal heart rate compared to an average of 56 percent of maximal heart rate during the non-heated experience. The intensity of each class—according to fitness industry guidelines—would be categorized as “light” exercise.


“Yoga has significant benefits – from muscular strength and endurance to flexibility and balance, in addition to its mind-body value,” said Bryant. “For those looking to participate in hot yoga of any kind, it’s important to properly hydrate before, during, and after class while also monitoring for early signs or symptoms of heat intolerance (e.g., headache, muscle cramps,  nausea, dizziness, or fatigue).”

To download a full copy of the hot yoga study, visit


About ACE
Since 1985, American Council on Exercise (ACE) has evolved from a small nonprofit dedicated to educating people about proper fitness to a 50,000-strong network of certified Personal Trainers, Group Fitness Instructors (GFI), Health Coaches and Advanced Health & Fitness Specialists (AHFS). As the largest NCCA-accredited nonprofit fitness certification organization in the world, ACE provides quality continuing education to professionals and conducts independent science-based research to protect all Americans from unsafe and ineffective products. Our goal is to inspire people to live their most fit lives through free fitness resources including workouts, nutrition information and expert advice. 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.



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