Algorithm to calculate human calorie expenditure based on a predicted heat strain model

A predicted heat strain model (PHSM) has been used to evaluate the thermal stress experienced by a human subject during exercise in a hot environment. In the PHSM, equations describing the thermal balance of a human body predict the physiological response, including sweat rate and internal temperature, for a given metabolic rate. In this paper, we propose that the heat balance equations of the PHSM may be used in reverse, to calculate the metabolic rate from physiological and environmental sensor readings. We develop distinct algorithms for ordinary situations, as well as a common, extreme case, in which the heat strain exceeds the body's ability to dissipate heat through evaporation of sweat. Compared with the algorithm currently used in commercial calorie expenditure monitors, the new algorithm we propose may provide a more reliable and precise calculation.