Sudomotor responses from glabrous and non-glabrous skin during cognitive and painful stimulations following passive heating
Aim: It is widely accepted that thermal and psychological sweating are independently controlled and respectively restricted to non-glabrous (hairy) and glabrous skin. These assumptions were evaluated in six experiments conducted across eight body segments, in which 38 glabrous and non-glabrous skin surfaces were investigated. Methods: Sweating was measured in 30 passively heated individuals using ventilated sweat capsules, with passive heating used to first establish steadystate sweating, averaging 0.30 mg cm-2 min-1 (+-0.03) across all sites, prior to the application of cognitive and painful stimuli. Results: These non-thermal (psychological) stimulations significantly increased sweat secretion at more than 70% of the sites investigated [cognitive: 28 of 38 sites (P < 0.05); pain: 23 of 32 sites (P < 0.05)], eliciting peak sweat rates averaging 0.51 mg cm)2 min)1 (+-0.05) and 0.47 mg cm-2 min-1 (+-0.4 respectively) across all sites. Furthermore, nonthermal sweating was evident from both the glabrous and non-glabrous surfaces and occurred without mean body or local skin temperatures changes (P > 0.05). Indeed, neither thermal nor psychological sweating was restricted to discrete skin surfaces, and there were no consistent sudomotor differences between these two skin classifications. Finally, at no site was thermal sweating inhibited during a non-thermal stimulation. Conclusion: These generalized sudomotor responses challenge the hypotheses that glabrous skin sweating is driven by psychological stimuli, and that thermal sweating is a phenomenon restricted to the non-glabrous skin surfaces.