Thermal heat production in humans
Energy in the human body comes from the food consumed. Human daily energy intake nearly equals the daily energy production because there is negligible storage of energy in terms of fat or in growth processes such as that of bone or muscles. After food ingestion, catabolic processes associated with digestion will increase energy production for up to six hours after the time of ingestion. Only digestible food rich in protein and carbohydrates contributes to this increase.
The amount of heat produced by an individual depends on the calories consumed subtracting any mechanical work done. For example 2400 kilocalories can produce 116 watts of energy in a single day. The greatest amount of heat in the body comes from muscle activity. Most of this heat comes from the larger muscles like those of the arms and the legs. For instance during cold seasons this heat is utilized by poikilotherms to warm themselves.
The temperature at the body surface of the human being is strongly associated with heat generation. The human body can be compared to a machine which converts fuel into energy to do work. The more active the body is the more energy it will produce. Metabolic rates are used to measure the amounts of heat produced by the body as a result of various chemical reactions. The table below provides examples of activities that generate heat. The figures are in watts.Sample Essay of Masterpapers.com