Energy metabolism & physical work

 The process of liberation, transformation and utilization of energy in the human body is known as metabolism. 

 Operations of the body organs such as muscle construction, blood circulation, breathing etc. purposes; human must oxidize food & convert it into electro

chemical energy. 

 20% energy is converted by oxidizing food & 80% as heat. 

 The rate at which human body generates heat is known as metabolic rate. 

 The metabolic rate is the heat released from the body per unit skin areas expressed as met unit. 

 1 met = 18.4 Btuh/ft2 = 58.2 W/m2 = 50 K. cal/m2 .Hr. 

 Average human body skin area normally 1.7 Sq.M. 

 Hence, for an average size man, the met units corresponds to 1.7 × 58.2 = 100 W = 360 Btuh = 90 K cal/hr. 

 Generation of heat and energy by the human body depends on the human activity level at any time.  During sleeping lowest amount of energy is required , hence lowest amount of heat and energy is produced and lost. 

 During very hard working higher amount of energy is required and higher amount of energy and heat is produced and lost. 

 Metabolism rate for different activity level of human body is shown below :