Metabolic Heat Production

The human body produces heat due to biochemical reactions taking place in the body. This heat production is characterized by the base metabolic rate ${\dot{Q}}_{MET,BAS}$, which is always present to keep the human alive, and a portion of the metabolic rate due to activity. The activity portion consists of the muscular work ${\dot{Q}}_{MET,WORK}$ and, if applicable, the shivering due to cold ${\dot{Q}}_{MET,SHIV}$.

When computing the heat production through muscular work, a mechanical efficiency of zero is assumed. This assumption is valid for most types of physical activity. The core, fat, or skin elements do not influence the heat production, because the metabolic work ${\dot{Q}}_{MET,WORK,TOT}$ takes exclusively place within the muscles. The metabolic work has a local constant $L_{MUS,WORK}$ that is used to distribute the heat production to the individual muscle elements. The equations for computing the metabolic heat production are as follows:

Core:

Muscle:

Fat:

Skin: