The development of the computer led to dynamic and integrated representations of the human body, human thermoregulation and heat transfer between the body and the environment. Some of computer models represented the body to include body parts such as the head, hands, feet and more and therefore have application in cold environments. A mesh or network of closely knit points leads to finite element, finite difference or finite volume methods and is solved by a matrix of equations. If point or node is representative of the ‘state’ of a whole region of the body lumped together, the models are often called ‘lumped parameter models’. Heat transfer is determined within the body between compartments including blood, and with the environment by convection, radiation and evaporation. The dynamic nature of the model is simulated by starting at a set of initial conditions (e.g. for comfort) and adjusting those conditions over time (e.g. every minute) depending upon the consequences of the physiological responses.