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.