Thursday, January 16, 2014

Hot Yoga May not be so Cool.

Yoga is good for the body and mind. It promotes relaxation, health and calmness. Unless a person is suffering from large joint osteoarthritis or spinal injury it is helpful in maintaining good body conditioning. But hot yoga is not the same.
The human body and most living things have a fine tuned system that works with checks and balances to keep us alive and healthy for the most part. Confusing the body’s feedback and homeostasis systems can causes serious problems.

Hot yoga has that potential.


Source: Bikram Yoga Instructor Training Advertisement

Exercise and the body’s response

Conventional vigorous exercise accelerates our respiration rate which is a good thing. It helps carry wastes and toxins such as carbon dioxide out of the body through the lungs. At the same time it helps increase
oxygen intake. Our systems detect the resulting rise in temperature due to the vigor of the exercise and triggers a perspiration response which oozes water out of pores in the skin and, upon evaporation, helps cool the body down. The more rapid the exercise rate, faster the heart beats, higher the need for oxygen, more the respiration, and as a consequence, more the water loss due to perspiration. This is what is considered normal exertion.

By design there is little fresh air exchange in a hot yoga room as that would be self-defeating. The temperature has to be maintained above 105 degrees along with extreme humidity kept up at 40% or higher. (As per Bikram Choudhury, founder of hot yoga)

Fooling the system.

When the body is exogenously heated, rather suddenly, as is the case upon entering a hot yoga session, it is taken by surprise. It takes a runner, a gymnast, or a weight lifter several minutes to warm up the body to start sweating. It would take a yogi considerably longer.

In the case of the runner, the body adapts to that change by raising the heart rate to keep pumping blood to keep up with the motion, and since blood is moving faster through the arteries and veins, the respiration rate is also ramped up to provide for more oxygen transfer. As the body heats up blood is moved to the sweat glands which ooze out water from the plasma pushing it out to the skin’s surface. The resulting draft from moving rapidly through air while running provides plenty of opportunity for moisture to escape and maintain the cooling effect.

In hot yoga, the system tries to accomplish the same but with dismally poor results. Water, or perspiration droplets make it out of the skin pores but little evaporation and cooling can take place because of the high humidity, and must be wiped off constantly.

The heart is still not pumping at a higher rate since there is passive physical activity. Ultimately the body starts to catch up, the heart rate starts to pick up as a result of the loss of water, which forces the respiration to pick up. Unfortunately the captive air besides being hot and humid, is oxygen deficient and carbon dioxide rich; more people inhaling and exhaling and little or no ventilation. Oh yes! You do lose water, and hence the weight associated with it.


Source: NOAA
If you were to use the guide and recommendations provided by the National Ocean and Atmospheric Administration you would notice the intersection of 105 degrees and 40 % humidity is already in the danger zone, a heat index of about 125 degrees. Some hot studios run at higher ( 110 degrees) temperatures and 60% humidity. One can see how risky spiking the heat index to critically harmful levels can be.

Those who are unable to endure the rigors of artificially elevated temperatures and humidity levels, may find themselves suffering from stomach cramps, dizziness, nausea and heat stroke. This can be compounded by severe lack of oxygen in the enclosed area.

Some risk factors to watch out for are people taking beta blockers, diuretics, vasoconstrictors, antidepressants and antipsychotics, stimulants to treat ADHD, as well as those who use recreational illicit drugs such as meth and cocaine. Those who have chronic heart or lung disease including asthma should avoid hot yoga altogether.
As a safety precaution do consult your physician before stepping onto a hot yoga mat.


Sources:
Examiner.com. "Don't sweat it: The skinny on exercising in a hot environment - Chicago Health & Wellness." Accessed January 16, 2014. http://www.examiner.com/article/don-t-sweat-it-the-skinny-on-exercising-a-hot-environment.
++ Mayo Clinic - Mayo Clinic. "Heatstroke Risk factors - Diseases and Conditions - Mayo Clinic." Accessed January 16, 2014. http://www.mayoclinic.org/diseases-conditions/heat-stroke/basics/risk-factors/con-20032814.
++
NOAA Heat Index guide.

How to read the chart...Follow the temperature line until it intersects the relative humidity line. Then read the Heat Index on the curved line. For example, an air temperature of 100°F and Relative Humidity of 40%. Follow the 100°F temperature line until it intersects the 40% relative humidity line. Then curved line that also intersects is the Heat Index of 110°F, or Very Hot. That is the temperature the body thinks it is and attempts to compensate for that level of heat. Remember, these values are in the SHADE. You can add up to 15°F to these values if you are in direct sunlight.
The table below tells you the risk to the body from continued exposure to the excessive heat.

Category
Classification
Heat Index/Apparent Temperature (°F)
General Effect on People in High Risk Groups
I
Extremely Hot
130°F or Higher
Heat/Sunstroke HIGHLY LIKELY with continued exposure
II
Very Hot
105°F - 130°F
Sunstroke, heat cramps, or heat exhaustion LIKELY, and heatstroke POSSIBLE with prolonged exposure and/or physical activity
III
Hot
90°F - 105°F
Sunstroke, heat cramps, or heat exhaustion POSSIBLE with prolonged exposure and/or physical activity
IV
Very Warm
80°F - 90°F
Fatigue POSSIBLE with prolonged exposure and/or physical activity

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