title: Morphological dependency of cutaneous blood flow and sweating during compensable heat stress when heat-loss requirements are matched across participants.
abstract: Human heat loss is thought, in part, to be morphologically related. It was therefore hypothesized that when heat-loss requirements and body temperatures were matched, that the mass-specific surface area alone could significantly explain both cutaneous vascular and sudomotor responses during compensable exercise. These thermoeffector responses were examined in 36 men with widely varying mass-specific surface areas (range, 232.3-292.7 cm(2)/kg), but of similar age, aerobic fitness, and adiposity. Subjects completed two trials under compensable conditions (28.1°C, 36.8% relative humidity), each involving rest (20 min) and steady-state cycling (45 min) at two matched metabolic heat-production rates (light, ∼135 W/m(2); moderate, ∼200 W/m(2)). Following equivalent mean body temperature changes, forearm blood flow and vascular conductance (r = 0.63 and r = 0.65) shared significant, positive associations with the mass-specific surface area during light work (P < 0.05), explaining ∼45% of the vasomotor variation. Conversely, during light and moderate work, whole body sweat rate, as well as local sweat rate and sudomotor sensitivity at three of four measured sites, revealed moderate, negative relationships with the mass-specific surface area (correlation coefficient range -0.37 to -0.73, P < 0.05). Moreover, those relationships could uniquely account for between 10 and 53% of those sweating responses (P < 0.05). Therefore, both thermoeffector responses displayed a significant morphological dependency in the presence of equivalent thermoafferent drive. Indeed, up to half of the interindividual variation in these effector responses could now be explained through morphological differences and the first principles governing heat transfer.
authors.affiliation: Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia; and.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Notley
authors.affiliation: Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia; and.
authors.forename: Joonhee
authors.initials: J
authors.lastname: Park
authors.affiliation: Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia; and.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tagami
authors.affiliation: Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia; and Faculty of Nursing, Mie Prefectural College of Nursing, Mie, Japan.
authors.forename: Norikazu
authors.initials: N
authors.lastname: Ohnishi
authors.affiliation: Centre for Human and Applied Physiology, School of Medicine, University of Wollongong, Wollongong, New South Wales, Australia; and nigel_taylor@uow.edu.au.
authors.forename: Nigel A S
authors.initials: NA
authors.lastname: Taylor
mesh_terms: D050154:Adiposity / Q000502:physiology; D000293:Adolescent; D000328:Adult; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005542:Forearm / Q000098:blood supply / Q000502:physiology; D018882:Heat Stress Disorders / Q000503:physiopathology; D006358:Hot Temperature; D006801:Humans; D008297:Male; D012039:Regional Blood Flow / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012867:Skin / Q000098:blood supply*; D013312:Stress, Physiological / Q000502:physiology*; D013546:Sweating / Q000502:physiology*; D014666:Vasomotor System / Q000502:physiology; D055815:Young Adult
keywords: cutaneous blood flow; heat exchange; morphology; surface area; sweating