The human body is able to maintain a fairly constant temperature under varying environmental conditions. To do this, it must be able to gain or lose heat. The core temperature is regulated to remain relatively constant, but the temperature of the shell, the skin and the tissues directly beneath it, varies directly with environmental conditions. The hypothalamus in the brain controls the body temperature and calls into play either heat loss or heat production mechanisms. Regulation comes in response to changes in the skin or blood temperature.
Normal metabolism in the body produces heat. Increased heat production can come from higher metabolic rates, disease, shivering or exercise. During exercise, the increased metabolic rate and energy production both generate heat. Most of the heat gain is due to the lack of efficiency of the body. It converts only 20-25% of energy produced into work; the rest is dissipated as heat.
Heat loss is governed by the following physical means.
Four environmental factors can interact to change the effectiveness of evaporation mechanism. They are air temperature, relative humidity, air movement, and radiation. Caution should be advised when the temperature is above 80 F or when the relative humidity exceeds 50-60%. A small breeze will help keep the body temperature near normal by helping to evaporate sweat. Radiant heat absorbed from the sun by the body will add to the heat load.
Fluid and Electrolyte Replacement