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I keep hearing this nonsense about doing exercise in a hot room such as yoga. I am finding that the general public is very misinformed about human physiology and how our bodies react to exercising in hot climates. This is the first part of a 2 part article designed to give people some important information about what is exactly happening to their bodies when they attend these hot workouts, and how they may even be increasing their risk of heat exhaustion and heat stroke. I will also attempt to show you how many of the claims are completely false.

This is a short list of the most persistent claims I typically found about hot yoga on the internet.

Increased heat of the room allows for better flexibility and stretching

Increased heart rate allows your body to more easily burn fat and gives a cardiovascular workout

Increased Sweating helps your body eliminate toxins

Lets look at each one of these in more detail from a scientific standpoint.

Increased Temperature means increased flexibility
Increased core body temperature of approximately 3 degrees has been shown scientifically to be the threshold where connective tissues like ligaments, tendons and muscles become more elastic and flexible. This temperature increase has been shown to be possible with exercise. For example 20 minutes of cardio such as running or biking can get your core temperature up enough. External heat like heat patches applied directly to muscles have been shown to be ineffective at increasing the temperature of these tissues. If these hot workouts provide an increase in flexibility I have yet to find research to substantiate it. But if you like the way it feels I cant argue with anyone on that point.

Increased Heart Rate means increased fat burning and cardio fitness
The increase in heart rate you get from exercising in the heat is a result of excessive fluid loss from profuse sweating. The heart has to pump more often because there is less blood volume per beat. This is an early sign of dehydration. This has nothing to do with fat burning or cardiovascular fitness. This will also cause you to fatigue prematurely and cause your body core temperature to heat up even more as now your heart is working even harder. This starts a vicious cycle of increasing body temperature and sets you on a path to heat illness or heat exhaustion.

Excessive sweating causes you to sweat out toxins
Sweat does not remove toxins, this is a complete lie with no scientific proof at all. The only potential way sweat could be used for detox is rehab from drug addiction if at all. In these cases the rehab should be under the supervision of a medical practitioner, and even this is very poorly represented in the scientific research and mostly shows up in alternative medicine articles. Sweating in hot environments is your bodies way of cooling down through evaporation of water. In a humid room the sweat is much less effective at cooling your body down. Toweling the sweat off also interferes with the ability of the sweat to cool your body off. If the room is humid (and from what I am reading hot yoga rooms are meant to be at approximately 50% humidity) the sweat is even less effective at cooling you off. This starts a vicious cycle of your body temperature increasing, then your body sweats more to try and cool you off, and then you become more dehydrated. This is also a dangerous situation if you stay in the heat for too long. All of this extra sweating is just a recipe for dehydration and heat exhaustion. There is simply no such thing as sweating out toxins. This is an idea that has been laid to rest by the scientific medical community decades ago. The fact that it still persists in pop culture is absolutely ridiculous.

Part 2 of this article will explain heat acclimatization, why I think this hot workout trend is simply a marketing angle, and some of the real benefits of yoga.

John Barban is a certified Strength and Conditioning Specialist and a varsity strength and conditioning coach. His trademarked http://www.6minuteCircuits.com Circuit Training Workouts have helped thousands of women with weight loss and fat burning in less than 45 minutes three times per week. http://www.grrlathlete.com John's female sports training articles will help you burn fat without long, slow cardio sessions or fancy equipment. You can ask John a question on the http://www.grrlathlete.freeforums.org a womens workout forum to help you lose fat and get in shape with circuit training and nutrition.

posted by 46124  # 12:58 AM