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Bikram Yoga Sweat: Stumping the Rocket Scientists.

It started innocently: one day the Bikram Yoga room felt a little cool and I had come to get my sweat on! C’mon. What was going on here? This is Bikram Yoga. You know, the “torture chamber.” Here I was, being tortured by a cool breeze and goose bumps.

What to do? Add clothing. Problem solved.

If you haven’t practiced any sort of hot yoga, here’s the quickie summary: by adding heat and humidity, the body becomes more flexible, and the workload increases. The heart rate goes up and the sweat trickles down. In a nutshell, the higher the heat and humidity, the harder the class is. All 26 poses in the 90-minute Bikram Yoga sequence are beginner poses with very little movement. Without excruciating heat and humidity, it’s a cakewalk (or in Bikram parlance, a blueberry cheesecake walk). 

bikram sequenceGET HOTTER

I now come prepared to any hot yoga class. I have layers to add if the room isn’t up to snuff.  But, over the years teachers have bristled at this behavior. “Get your head out of the heater Erin.” Not so easy. I am there to work hard. The heat, humidity, AND poses deliver. ALL three. This yogi can’t balance on a 2-legged stool.

THE SCIENTIFIC CHALLENGE PRESENTED

Recently a teacher sent me a link to a WebMD article suggesting that layers, once wet, will make me feel cooler NOT hotter. The article specifically says “wet clothing greatly increases heat loss through conduction and evaporation.” What?? How could this possibly be? Shouldn’t my sweat warm up in that heat box? Adding layers, trapping heat, covering the skin…all of these strategies should keep me warm, right? Even when I sweat?

The Bikram/Hot Yoga environment is unique and articles like the one just mentioned don’t apply. The WebMD article is talking about temperatures under 68F (not Bikram). We all know wet clothing makes us cooler when the surrounding temperature is lower than our body temperature (think wet swim suit). But this is not the case in a hot yoga room. So we begin to dig.

Our athletic-minded traveler research team could not find ONE article, study, or research piece that dealt with OUR SPECIFIC situation: 105+ degree heat and relative humidity of 40-50% AND the desire to be hot…even hotter. We even went beyond the “research.” We contacted no fewer than 10 experts – in thermophysics, human performance, exercise science, neuromuscular function, and even a few authors of exercise physiology textbooks. Two dropped the ball, a few missed the point of contention (with ONE exception), and those that did reply gave us migraines with a bunch of scientific gibberish that said nada. Had we stumped the rocket scientists?

Let’s first get you up to speed about the body’s cooling mechanisms (thermoregulation). Understanding these basics is important.

BODY COOLING

  1. Radiation: transferring heat from one mass to the other without physical contact. Ever stood next to someone who just got done with a tough workout? They’re radiating heat! No need to touch…it’s coming off them like an oven with the door open.
  2. Conduction: losing heat through physical contact with another object or body. If you’ve ever sat on a freezing cold metal chair, then had the area under your butt become warmer, you’ve transferred the heat from your body to the cold metal chair.
  3. Evaporation: losing heat through the conversion of water to gas—SWEATING.
  4. Convection: losing heat through the movement of air or water molecules across the skin. This helps conduction and evaporation. Heat loss from convection depends on airflow across the skin. If you’re in a gym with industrial fans blowing, or in a Bikram studio with air movement, convection kicks in and you should cool down.

thermometerNow, let’s apply the above to working out. 80-85% of cooling during prolonged exercise comes from evaporationSWEAT! In humid environments like a hot yoga room, evaporation is slowed because the air already has a high level of moisture in it. There’s less “room” for the sweat to evaporate into the atmosphere. So if the body can’t sweat as efficiently, guess what? You feel hotter!

So when you’re in a Bikram class, with temperatures in excess of 105° F and relative humidity between 40-50%, it’s going to affect thermoregulation. With constant heat radiation from yogi to yogi, high humidity preventing sweat evaporation, and little to no airflow across the skin, it should be as easy as child’s pose to stay warm in class. But most Bikram Yogis don’t want warm. They want HOT.

 THE LAYERING QUESTION

  1. Does adding layers work? Yep. More layers should mean an increase in body temperature, especially in hot and humid Bikram studios.
  2. Do clothes curtail the evaporation process? Likely. All clothes get wet quickly due to the humidity. Could those wet clothes actually cool the body? Only if a strong gust of wind is blowing. It’s still likely the cooling is no more than bare skin and most likely less.
  3. Are we better off wearing as little clothing as possible? Not if you are trying to up the workload.
  4. How about adding as much clothing as possible? Go ahead! People will think you’re a bit “loco.” 

So listen up YOGIS:  Nah, nah, nah, na, nah, nah…We are RIGHT. Yes, a little childish…but hey we spent a LOAD of time on this! 

Our review of research (over 48 studies on MEDLINE) and email conversations with scientists suggests that layering WILL increase the workload because the body's evaporation is slowed. Along with studies that suggest this conclusion, a professor of neuromuscular function at Colorado State University corroborated our findings that layers of clothing reduce evaporative cooling (which accounts for 80-85% of the body's cooling during exercise). Hooray! He understood our question because he understands Bikram yoga!

The studies we found aren’t perfect. They don’t address heat, humidity, exercise, AND wanting to STAY WARM! Every study assumes you want to cool the body.

RESEARCH SUPPORT

  1. Sports Medicine (2003) says layers impose a barrier and in warm temps, increases body temp during exercise and slows evaporation. BINGO! BUT, what about wet clothing? Hmmmm…
  2. Another study (AIHAJ 2002) looked at clothing ventilation and thermal insulation. The results? More airflow through the clothing, the cooler the skin. Am I supposed to wear a garbage bag to class now vs. the “wicking” materials present in nearly ALL sport clothing?
  3. A study out of China looked at heat strain while wearing different ensembles for varying workloads. Simply put, you need to restrict sweat evaporation and exercise to increase heat strain and heat production.
  4. In a 1995 article from Ergonomics, protective clothing impeded heat exchange through sweat exchange for those working in hot environments. But…the specifics of “protective clothing” were not shared, so there’s no way to tell if it’s something we wear already!

Bottom line is this: those teachers who say layers can cool you down can zip it! Unless a constant breeze is blowing through the room, this just isn’t true. Those teachers that want you to get your “head out of the heater” should do the same. It’s all about personal preference, and if there’s a need to increase my heat, so be it. If I’m fine with the increase in workload, it’s my option to add layers. Bikram yoga is about the heat…it’s the honest truth. Those schools that coddle students with fans and open windows are missing the point, and we would guess they’re missing business too.

** This article was written by Daniel Gaz and Erin Kaese. Along with Dan's clinical research work at Mayo Clinic, he is also a contributing editor to Athletic-Minded Traveler. Erin Kaese is Managing Editor of Athletic-Minded Traveler and a Bikram Yoga "loca."

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Comments

Comments

This article was extremely

This article was extremely interesting and I like how it depends on one's personal preference to choose to work out with more layers or not. I have never tried Bikram Yoga, but after reading this article I would like to try it due to it's intensity of heat and humidity and a chance to really push my body. This would be an interesting workout and challenge to attempt. I like the idea of the extreme elements involved. I agree with this article because of the fact that I like to sweat when I work out and layering up in any conditions may contribute more significantly to sweating. I really like the idea of getting a better stretch in my muscles due to layering up and the high heat and humidity.

I found the article very

I found the article very interesting with the relationship of yoga and extreme heat. For me personally, I would not enjoy the idea of layers and high temperatures while working out. Living in the South the humidity is high and so are the temperatures and working out in these conditions in a few layers is enough for me. However, I can see how people who want to increase their weight loss and try a different workout, that layering and participating in Bikram Yoga could do the trick. A person needs to be aware of body temperatures that can increase the risk of health related issues. Water intake should be plentiful and layers should come off before a person becomes ill. It could worth a try if you already enjoy yoga and would like a challenge. I will pass this information on to my yoga friends and see what they think. Maybe they will be willing to take a class of Bikram Yoga, they are always looking for new classes to take.

A very interesting article,

A very interesting article, indeed! I have heard of Hot Yoga, but mostly through reading celebrity magazines, as it has been considered a "Hot" new trend! In the past, I have tried regular yoga, and failed miserably. I just cannot seem to get the movements in sync with trying to pay attention to what comes next. That said, I would imagine that increased body heat would include increased weight loss. However, could it be that much of the initial weight loss be water weight? I would believe that after the first few sessions, you would indeed tone up, but not necessarily lose weight. Also, there is a risk of developing a heat related illness, even though you are not necessarily out in the heat. Does anyone remember that group of people in Arizona that were at a retreat, and made to sit in a heated, enclosed tent for hours? Granted, that behavior is a little more extreme, but still a brings up a cause for concern. So, for myself, I am a bit skeptical, but I do see that it could offer benefits, especially if you are wanting to feel the effects of the workout quickly.

I found this article to be

I found this article to be very interesting. I have heard of “hot yoga” before, but was not exactly sure of the purpose, or how it was taught. It is true that everyone goes into exercise classes with their own mind set of what they want to gain from the exercise. Some people really like to sweat and work hard, and some people take it a little easier. Modification is important when taking a class, and learning what your personal capabilities are, become evident the more you engage in the class. After learning about thermoregulation and exercise in this course, the more the “hot yoga” makes sense. In the article, she talks about how she goes to the yoga class to work harder. She wants to be warmer, so her body is working harder. Thermoregulation is important to maintain and understand, because the hotter the environment, the more your body has to work; resulting in an increase in cardiovascular strength and fitness. I also agree with the article that not every workout is made for everyone. They are very individual, and subject to one’s needs. In this case, she wanted to push herself further and further, while others possibly engage to relax. Also, layering up during class can trap the heat longer as your body works to try to conduct, evaporate and perspire heat. Sometimes you see people in the gym wearing hooded sweatshirts and sweat pants while running on the treadmill, this is because they want their bodies to stay warm, trap in the heat so they work harder, burn more calories, and ultimately get the most out of their workout as possible. They do make special clothing for those looking to stay warm, or for those who want to whisk away sweat to stay cool. I found this article to be pretty interesting, and I am more aware of certain types of exercises that take place in heat, and how your body can benefit from that. I think I need to try it!

I definitely agree with this

I definitely agree with this article. Think about stepping into a room that is 100 degrees Fahrenheit vs. stepping into a hot tub that is the same temperature. The the pool feels much warmer than the air because liquid is a better conductor of heat than air (Physics.info). So liquids (sweat) conduct heat better than gasses (air), from which we can draw that, without evaporation, if our bodies were soaked in body temperature (or higher, room temperature) sweat, we would be warmer than if we were completely dry. Now to take evaporation into consideration. When sweat evaporates it has a cooling effect on the surface of your skin because the hotter molecules of water are able to break free leaving the cooler molecules behind (aip.org). So when you are wearing a layer, or multiple layers, of clothing, the evaporation process is cooling the surface of your clothing, rather than the surface of your skin. In a cold setting, layers of wet clothing will conduct that cold air temperature to your skin which may prove to be worse (colder) than bare skin, however, in a hot room, this wet clothing is conducting the room heat to your skin, and insulating your already warm skin by keeping a degree of your body heat next to it.

http://physics.info/conduction/
http://www.aip.org/dbis/stories/2004/14105.html

This is a great article. I

This is a great article. I for one am interested in trying Bikram yoga. I will probably not be putting on layers to warm up, but the thought of getting a far better stretch due to the warmer environment is appealing. I look forward to seeing if any research directly related to Bikram yoga surfaces in the near future.

I completely agree with this

I completely agree with this article! I took an exercise class at another college and I was actually scolded by my professor for exercising in a sweatshirt and sweats. She said I could pass out from the heat and it is not healthy for my body. What she didn't realize is that is how I have worked out for years! I work-out to sweat, plain and simple. Taking off layers or wearing less layers is not always going to help me get my sweat on. Thank-you for writing this, it has cleared up my own concerns in the matter and it feels good to know I can now 'layer up' when working out.

Shelby thanks for that

Shelby thanks for that comment. Glad we were able to clear things up for you.

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