The human thermoneutral and thermal comfort zones: Thermal comfort in your own skin blood flow.

Human thermoregulation is achieved via autonomic and behavioral responses. Autonomic responses involve 2 synchronous 'components'. One counteracts large thermal perturbations, eliciting robust heat loss or gain (i.e., sweating or shivering). The other fends off smaller insults, relying solely on changes in sensible heat exchange (i.e., skin blood flow). This sensible component occurs within the thermoneutral zone [i.e., the ambient temperature range in which temperature regulation is achieved only by sensible heat transfer, without regulatory increases in metabolic heat production (e.g., shivering) or evaporative heat loss (e.g., sweating)].(1) The combination of behavior and sensible heat exchange permits a range of conditions that are deemed thermally comfortable, which is defined as the thermal comfort zone.(1) Notably, we spend the majority of our lives within the thermoneutral and thermal comfort zones. It is only when we are unable to stay within these zones that deleterious health and safety outcomes can occur (i.e., hypo- or hyperthermia). Oddly, although the thermoneutral zone and thermal preference (a concept similar to the thermal comfort zone) has been extensively studied in non-human animals, our understanding of human thermoregulation within the thermoneutral and thermal comfort zones remains rather crude.