The Main Physiological Mechanisms of Cold Adaptation in Humans.

This article reviews published data on the main types of adaptation of humans to cold and the mechanisms increasing heat production. Studies in recent years addressing the molecular mechanisms of adaptation to cold are shown to confirm results from earlier physiological investigations demonstrating that the main contribution to adaptive thermogenesis on cooling is provided by oxidative fibers in skeletal muscle (birds, marsupials, large placental mammals, and humans) and brown fat (small placental mammals, particularly rodents). The main increase in heat production occurs as a result of contractile activity (shivering and thermoregulatory muscle tone), uncoupling of oxidative phosphorylation, and decreases in the efficiency (energy conversion efficiency, ECE) of cellular pumps (ATPases), which is induced by noradrenaline and thyroid hormones and is accompanied by increases in the consumption of oxygen and energy substrates. Prolonged cold adaptation leads to increases in the number and activity of mitochondria to provide for increasing levels of ATP consumption. [ABSTRACT FROM AUTHOR]