More and more it seems there are two types of yogis. Those who flock to heated humid rooms to sweat every last ounce of water from their bodies and those that practice at ambient temperatures. Many yogis are attracted to the more “physical” nature of heated yoga and its “detox” properties. But does hot yoga really live up to the benefits its enthusiasts swear by? And more importantly is it safe?

A recent study by the American Council of Exercise asked whether hot yoga was a more challenging workout than normal yoga. The answer was a resounding no. On day one, study participants were led through a 60-minute yoga class. The next day, the same instructor led the same people through exactly the same class except that the room was 22 degrees hotter than the day before (71 vs 93 degrees).

When surveyed participants felt like they were working significantly harder in the hot yoga class compared to the normal yoga class. Turns out they weren’t. Participants swallowed a device that measured their core body temperature every 5 minutes and their heart rate was recorded every minute during the yoga classes. Hot yoga didn’t raise participant’s heart rate or core body temperature compared to the normal yoga class.

Heart rate is the major determent of how many calories you burn (gender, age, and weight are also important but fixed in this case).  Core body temperature can be thought of as a correlate of metabolism, as the body works harder its temperature rises, metabolism increases and more calories are burned. But that didn’t happen either. So hot yoga didn’t burn more calories and participants weren’t physically working any harder. But yes they felt like they were working harder and they were drenched in sweat.

Speaking of sweat, let’s take a moment to debunk one of the biggest and most unfounded myths in the health and wellness world. Sweating does not release any appreciable amount of toxins from the body. I repeat sweating is not an efficient means of detoxification. Sweat is primarily water and salt along with very tiny amounts of urea, lactate,  and trace minerals/metals. That’s it.  Some people can excrete alcohol from the skin, but that’s the only caveat worth mentioning.  Detoxification happens at the level of the kidneys, liver, and lymphatic system. The purpose of the skin is to protect the body and regulate body temperature  not to “detox”.

Temperature regulation brings us back to the question of whether  hot yoga is safe. One concern was that that in heated yoga, the core body temperature may get dangerously high. This was not the case (at least under these specific study conditions). Core body temperature remained less than 104 degrees (highest recorded temp was 102), where stroke risk and permanent organ (namely brain) damage become a serious concern. It is important to note that the room was only 93 degrees. In Bikram Yoga the room starts at 105 degrees and in some studios gets as hot as 115 degrees, so it remains a possibility that core temperatures could climb to dangerous levels in hotter environments. In short, this study suggests that in your typical hot (not Bikram) yoga class if you are well hydrated and don’t have underlying medical conditions excessive core body temperature isn’t a major concern.

My issue with this study is that it doesn’t address the more immediate and more common risks of heated yoga. In a heated environment your muscles can stretch further and you have decreased pain perception. So unless you are well trained and very conscious in your movements the heat enables you to go further than your body may be ready for and you risk injuring your muscles and tendons. To date, there is no yoga-specific research, but all-in-all more general research suggests that overstretching is a likely concern in heated yoga classes. Other research shows that at temperatures over 80 degrees focus is impaired. In my personal experience, it is more challenging to focus on the details of a pose when I am powering though a sweaty class. If you feel like you are about to die or pass out, you probably aren’t too concerned with where your knee is pointed much less the subtle bandhas.   None of this means heated yoga is bad. Every activity has its risks. Simply take a step back and determine whether it is useful for you and worth the extra risks.

By and large, you get the same benefits in an unheated room and are probably less likely to injure yourself. There is some interesting psychology behind the appeal of workouts that are perceived as incredibly difficult due to a strenuous environment that is worth looking out. Some of us need intensity to get a release and others are sensation junkies. Either way so many people in our society need to feel pushed to the edge mentally and physically so we put ourselves in situations that make us feel like we are working our a@@ off. The authors of the above study explain that if you were to run or walk one day and then do it again on a hot day, you would see changes in physical parameters (e.g. increased heart rate). So this suggests that in hot yoga you aren’t pushing your self as hard physically in a hot room as you might in an unheated class, because you feel fatigued/challenged by the heat  and end up backing off on the intensity be it consciously or unconsciously.

I don’t mean to rain on hot yoga. I can appreciate the appeal and am known to take (and sometimes teach) a heated class from time to time,  but I am a stickler about the quality of the studio and teacher. What is most important is that you develop a practice that is safe, sustainable and feels good to your body. One that will last a lifetime.

If you love to get your sweaty yoga on, here are a few tips to keep your practice healthy.  I’d recommend that you are extra vigilant about alignment and listen to your body. So much of yoga is an exercise in self-awareness. It requires a lot of knowledge and awareness to practice heated yoga safely. You should feel sensation, but not pain in a stretch. The stretch should be in the belly of the muscle, not at the joint. In most cases you want to stretch a toned muscle. Keeping the muscle partly active will help prevent overstretching. Any tweaking or pain after class is an indication that something is awry -so go talk to your teacher or find one that knows their stuff.  Dehydration is also concern, so drink plenty of fluids before and after class.