It’s Not the Heat, It’s the Heat Index!

One of my least favorite things to do as a yoga studio manager is respond to rumors so I try not to. But once in a while a rumor persists or is of such a nature that it compels a response. This is one of those times.

SHY has not changed our heat policy or procedures and we have no plans to do so. We are a hot yoga studio and we continue to operate as close as possible to the industry standard of 105 degrees and 40% humidity for all of our Bikram Yoga and Hot Fix classes (Vinyasa and Advanced classes are conducted at approx. 95 degrees).

Two important caveats apply:

1) The individual temperature and humidity numbers are meaningless except in relation to each other.

105/40 is equivalent to a heat index of 120 (approx). If one of these two numbers changes the other must be adjusted accordingly. For example, 110/40 equals a heat index of 136 and 100/40 equals a heat index of 110. Our goal at SHY is to maintain the heat index level as close to 120 as possible without going over it.

2) Controlling the heat index in the yoga room is challenging due to our difficulty in making quick changes to humidity levels.

External conditions may change suddenly and significantly, particularly in regards to humidity. What we can change more easily and quickly is temperature so that number gets a little more attention. On days when the humidity is above 40 we maintain our desired heat index level by lowering the temperature accordingly. Likewise, in the winter we sometimes raise the temperature to accommodate for low humidity levels.

All of these examples represent a heat index level of approximately 120:

  • 105/40
  • 110/25
  • 95/65

Besides humidity, there are other challenges in maintaining consistent conditions in the yoga room including the number of people in the room and how much they’re sweating. The more people there are sweating in the room together the faster the humidity level is going to rise. On top of that, higher humidity means less evaporation of sweat from the skin which impedes the body’s ability to cool itself. A crowded class in summer can escalate quickly from challenging to unsafe. Safety is the single most important aspect of our mission statement.

The National Weather service tracks heat index levels throughout the country during the summer issuing advisories as it rises. As you can see in their chart below they consider exercising at a heat index of 120 to be approaching the border between Dangerous and Extremely Dangerous. This is one of the reasons that hot yoga is still controversial in many circles, especially amongst medical and health professionals who are unfamiliar with it.

  • Heat Index

Obviously, we believe practicing hot yoga is not only safe but substantially beneficial for the vast majority of people who try it. Our approach to asana practice includes an emphasis on gentle, mindful movement and intentionally slow deep breathing in order to minimize risk and maximize benefits. Is it safe for everybody? Probably not. Does everyone have the same response practicing asana at a heat index of 120? No.

I haven’t even mentioned C02 levels, which also must be considered. We don’t have state of the art C02 monitoring equipment so we have to use a crude, but effective, method: we open doors. When you see (or feel) a door being opened in the yoga room it is primarily in order to bring fresh air in and let some C02 out. This is a vital part of maintaining safe and optimum conditions for practicing hot yoga. None of what we do is based on my or anyone else’s individual preferences.

One Size Does Not Fit All

I experience dehydration and heat exhaustion symptoms when the heat index during class gets above 120. My optimum level is around 105. Yours may be different, lower or higher. This is exactly why we cannot create or maintain conditions according to the needs of any individual person. Our only choice is to strive to maintain an optimum level for an average range of people. For as long as SHY has been in operation I have been hearing your feedback about the heat. One of the ways I know I’m getting it right is when I hear just many complaints that it’s too hot as that it’s not hot enough.

We are fortunate in that our heating system is zoned. We have five thermostats in the room which allows us to allow the temperature vary a little in different areas. This allows us to create cooler areas and hotter areas. The difference isn’t pronounced but it’s generally a little cooler near the windows or towards the back of the room. The front left corner of the room tends to be a degree or two warmer.

Finally, I am aware a contributing factor that contributed to the recent spate of rumors about the heat at SHY. Management at SHY (meaning Rebecca and Eric) have an expression that we use with our instructors at the onset of the summer heat: “103 is the new 105!” This is simply a short-hand code for acknowledging that the humidity levels are getting high enough that we may need to adjust the temperature to compensate. It’s meant as a reminder of all of the above factors and conditions. It is not a statement of a policy change.

Written by Eric

Eric Jennings practices and teaches yoga in the style and method originated by Bishnu Ghosh, acclaimed Indian physical culturist. He holds certifications from Ghosh Yoga College of India (2016), Yogic Physical Culture Academy (2013) and Bikram Yoga, Inc. (2001). He has studied with Muktamala Mitra, Jared McCann, Mary Jarvis, Tony Sanchez, Marlysa Sullivan, William Huffschmidt, Yoganand Michael Carrol and Bikram Choudhury. With a background in theatre and performance one of Eric's strengths as an instructor is his ability to offer clear and accessible instruction making all practitioners, no matter their level of experience, feel safe, supported and encouraged in their practice.