The law of thermodynamics ensures that the researchers can account for heat into and out of the body without loss and hence conduct a thermal audit. For a constant temperature then the body must be in heat balance. If the researchers derive equations that quantify avenues of heat inputs to the body and heat losses from body they can set up a body heat equation and for constant temperature they can describe the body heat balance equation. An important starting point is that energy for body is generated in the cells by the metabolism of food. The total amount of energy produced is termed the metabolic free energy production in Joules or metabolic rate in Joules per second or Watts. Conduction is the transfer of heat by direct ‘contact’, from molecules of a substance to adjacent molecules of lower energy such as in one direction from one (hotter) end of a material, sequentially to the other end at lower temperature.