 Dear students, in this topic we shall discuss thermo regulation during exercise. You know that muscle contraction generates heat. During muscle contraction, the chemical energy is converted into mechanical work and heat. For every one joule of energy utilized in work, three joules of energy is degraded into heat. So, the energy efficiency of muscle contraction is only about 25 percent, which is used in work. 75 percent is dissipation as heat. When we do some type of exercise, it involves muscle contractions. So, it generates excessive heat. This heat adds to the basal metabolic heat, which is normally produced by the body. In this way, the added heat causes rise in body temperature above the set point. Temperature rises in proportion to the rate of muscular work. The extra heat generated is simultaneously dissipated to the environment. The maximum amount of heat produced by the body is simultaneously released. When we do some light exercise in cool environments, then the dissipation is balanced without any considerable rise in body temperature. However, for heavy exercise in warm environment, core body temperature can rise up to 4 to 5 degree centigrade above set body temperature. The heat dissipating mechanisms become unable to balance heat production at that moment. The rise in body temperature is controlled by a strong and steep increase in the rate of sweating. However, humidity affects the effectiveness of evaporative heat loss and duration of cooling. That's why heavy exercise in hot, humid environments is not advisable.