Impairment of entropy regulation in humans associated with age and illness: a calorimetric approach*

Complex living systems such as the human body are characterized by their self-organized and dissipative behavior where irreversible processes continuously produce entropy internally as energy is metabolized, and exported to the environment. We hypothesize that entropy regulation acts as a driver for the maintenance of physiological stability. In this presentation, we will introduce our experimental approach for the continuous measurement of entropy flows in the human body, here considered as a non-equilibrium and non-stationary system. The experimental protocols involved participants of different age groups (young/middle-age/old), fitness level (trained/untrained) and with or without Type 2 diabetes that performed exercise at varying intensity under heat stress in a calorimetry chamber. Metabolic heat production rates and total heat dissipation rates were recorded continuously using indirect and direct calorimetry, respectively, from which were calculated the rates of internal entropy production and external dissipation of the body. For fixed internal entropy production rates, we observed a progressive inability to externally dissipate entropy in older, untrained, or ill subjects, thus leading to greater entropy accumulation during exercise/heat stress, which we hypothesize is a measure of vulnerability. This research aims for novel insights and understanding of human regulation based on the study of the non-equilibrium thermodynamics.