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 addressed this very topic. Surveyed participants advised that they felt like they were working significantly harder in the hot yoga class compared to the normal yoga class, but it turned out they weren’t.

The participants swallowed a device that measured their core body temperature every five minutes and their heart rate was recorded every minute during the yoga classes. On the first day of the study, the participants were led through a 60-minute yoga class. The next day, the same instructor led the same people through the exact same class, except the room was 22 degrees hotter than it was the day before (71 vs 93 degrees).

As it turned out, hot yoga didn’t raise the participant’s heart rate or core body temperature compared to the normal yoga class. The answer as to whether or not hot yoga was more beneficial than ambient yoga was a resounding no.

Heart rate is the major determinant of how many calories we burn (gender, age and weight are also important, but fixed in this case). Core body temperature can be thought of as correlating with the metabolic rate—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 via 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 or not hot yoga is safe.

One concern was 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 it can get 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 a 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 perceived risks of heated yoga. To date, there is little to no yoga specific research, but all in all, more general research suggests that overstretching, dehydration, and heat exhaustion is a likely concern in heated yoga classes. Heat increases range of motion (e.g. flexibility) enabling the body to physically go deeper.

Heat also decreases the ability to detect pain.

If one is working through an injury or has mild arthritis this might be a positive thing. But it might cause us to ignore our body’s warning that we are treading into murky waters. Pain serves as a warning that something isn’t right and suppressing the pain response could become problematic if it is combined with poor alignment and/or a lack of muscular activation.

Other research shows that in temperatures over 80 degrees, or if a 2% decrease in hydration is experienced, it can impair our ability to focus. In my personal experience, it is definitely more challenging to target the intricate details of a pose when I am powering though an exceptionally sweaty and challenging class. If we feel like we are about to die or pass out, we probably aren’t too concerned with where our knee is pointed, much less with the subtle bandhas.  Using heat to go deeper into poses combined with decreased attention will inevitably elevate risk.

When it boils down to it, I am not against hot yoga per se, but rather unconscious yoga.

None of this means heated yoga is bad. Every activity has its risks. Simply take a step back and determine whether it is worth the extra risks. By and large, all evidence suggests we get the same benefits in an unheated room and are probably less likely to injure ourselves.

Sources:

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2. Nielsen B, Strange S, Christensen NJ, Warberg J, Saltin B. Acute and adaptive responses in humans to exercise in a warm, humid environment. Pflugers Arch. 1997 May;434(1):49-56. PubMed PMID: 9094255.
3. Reynolds CJ, Cleaver BJ, Finlay SE. Exercise associated hyponatraemia leading to tonic-clonic seizure. BMJ Case Rep. 2012 Aug 27;2012. pii: bcr0820114625. doi: 10.1136/bcr.08.2012.4625. PubMed PMID: 22927272.
4. Gopinathan PM, Pichan G, Sharma VM. Role of dehydration in heat stress-induced variations in mental performance. Arch Environ Health. 1988 Jan-Feb;43(1):15-7. PubMed PMID: 3355239.
5. Hooten WM, Hartman WR, Black JL 3rd, Laures HJ, Walker DL. Associations between serotonin transporter gene polymorphisms and heat pain perception in adults with chronic pain. BMC Med Genet. 2013 Jul 30;14:78. doi: 10.1186/1471-2350-14-78. PubMed PMID: 23895108; PubMed Central PMCID: PMC3737051.
6. Nakano J, Yamabayashi C, Scott A, Reid WD. The effect of heat applied with stretch to increase range of motion: a systematic review. Phys Ther Sport. 2012 Aug;13(3):180-8. doi: 10.1016/j.ptsp.2011.11.003. Epub 2011 Dec 29. Review. PubMed PMID: 22814453.

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