Bikram Yoga is practiced in a heated room to facilitate stretching and healing without injury.  There are many other reasons why the heat is beneficial.   

Bikram Yoga was developed in Calcutta, India where it is naturally hot most of the year.  When the series was brought to Japan in the late 1960's, students brought in heaters to warm up the room and started a trend that would serve to define Bikram Yoga.

Don't worry.  Your teachers know all about heat and relative humidity.  Try your best to let go of your fears.  Thousands of people are practicing this series in the same conditions all around the globe today.  I know it is hard to get used to the heat in the beginning.  There is a natural transition period in the beginning during which your body learns how to sweat more efficiently.  There is a method to the madness.  In the future you will be one of the students complaining that class was not hot enough!

There are 9 major reasons for the heat:

• The heat takes the trauma out of stretching.  Warm muscles are much less likely to pull or tear than cold muscles. 
• Oxygen is more readily supplied to warm muscles because of vasodialation of the capillaries.  That translates into better circulation to muscles, allowing for better delivery and removal of nutrients and wastes.
• Sweating is a major form of cleansing for the body.  Toxins and metabolic wastes are released through your sweat glands.  This, in turn, takes the strain off of the internal organs responsible for the removal of toxins like your kidneys and liver.  Give 'em a break!
• Fats and glucose are broken down and used more readily by warm muscles.  That means you burn more calories. 
• The warmth helps to prevent the deposit of fatty acids on arterial walls.  Stress and intense exercise causes a deluge of fatty acids in the blood stream.  Warm muscles are better able to utilize these fatty acids.  Cold muscles are not as efficient and excess fatty acids are deposited through out the body (eg. on your arterial walls).  While your internal temperature may not rise much during class (0.6 degrees average), your skin and superficial muscles will.  The heat helps keep those muscles as warm as your chest and abdomen.
• The heat improves coordination and balance.  Students practicing in a warm environment have an easier time with balancing postures and coordination of multi-step postures.
• The warmth of the room helps to prevent heart irregularities associated with sudden exercise.
• The human nervous system sends messages more readily when the body is warm.
• Helps you to develop tremendous will power, concentration and determination to learn to focus on your yoga and your breath in the midst of the intensity of the room and the distraction of the sweat dripping off your body.

        Adapted from "Smart Exercise" by Covert Bailey.