Relative contribution of core and cutaneous temperatures to thermal comfort and autonomic responses in humans

Subjective thermal comfort plays a critical role in body temperature regulation since this represents the primary stimulus for behavioral thermoregulation. Although both core (T(c)) and skin-surface (T(sk)) temperatures are known afferent inputs to the thermoregulatory system, the relative contributions of T(c) and T(sk) to thermal comfort are unknown. We independently altered T(c) and T(sk) in human subjects while measuring thermal comfort, vasomotor changes, metabolic heat production, and systemic catecholaminergic responses. Multiple linear regression was used to determine the relative T(c)/T(sk) contribution to thermal comfort and the autonomic thermoregulatory responses, by using the ratio of regression coefficients for T(c) and T(sk). The T(c)/T(sk) contribution ratio was relatively lower for thermal comfort (1:1) than for vasomotor changes (3:1; P = 0.008), metabolic heat production (3.6:1; P = 0.001), norepinephrine (1.8:1; P = 0.03), and epinephrine (3:1; P = 0.006) responses. Thus T(c) and T(sk) contribute about equally toward thermal comfort, whereas T(c) predominates in regulation of the autonomic and metabolic responses.