title: Distinct effects of blood flow and temperature on cutaneous microvascular adaptation.
abstract: OBJECTIVE
  We performed two experiments to determine whether cutaneous microvascular adaptations in response to repeated core temperature (Tc) elevation are mediated by increases in skin blood flow (SkBF) and/or skin temperature.
  
  
  METHODS
  Healthy subjects participated for 8 wk in thrice-weekly bouts of 30-min lower limb heating (40°C). In study 1, both forearms were "clamped" at basal skin temperature throughout each heating bout (n = 9). Study 2 involved identical lower limb heating, with the forearms under ambient conditions (unclamped, n = 10). In both studies, a cuff was inflated around one forearm during the heating bouts to assess the contribution of SkBF and temperature responses. We assessed forearm SkBF responses to both lower limb (systemic reflex) heating and to local heating of the forearm skin, pre- and postintervention.
  
  
  RESULTS
  Acutely, lower limb heating increased Tc (study 1, 0.63°C ± 0.15°C; study 2, 0.69°C ± 0.19°C; P < 0.001) and forearm SkBF (study 1, 0.13 ± 0.03 vs 1.52 ± 0.51; study 2, 0.14 ± 0.01 vs 1.17 ± 0.38 cutaneous vascular conductance (CVC); P < 0.001), with skin responses significantly attenuated in the cuffed forearm (P < 0.01). SkBF responses to local heating decreased in study 1 (clamped forearms; week 0 vs week 8, 1.46 ± 0.52 vs 0.99 ± 0.44 CVC; P < 0.05), whereas increases occurred in study 2 (unclamped; week 0 vs week 8, 1.89 ± 0.57 vs 2.27 ± 0.52 CVC; P < 0.05). Cuff placement abolished local adaptations in both studies.
  
  
  CONCLUSIONS
  Our results indicate that repeated increases in SkBF and skin temperature result in increased skin flux responses to local heating, whereas repeated increases in SkBF in the absence of change in skin temperature induced the opposite response. Repeated increases in Tc induce intrinsic microvascular changes, the nature of which are dependent upon both SkBF and skin temperature.
authors.affiliation: 1School of Sport Science, Exercise and Health, University Of Western Australia, Crawley, Western Australia, AUSTRALIA; 2Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, UNITED KINGDOM; and 3Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The NETHERLANDS.
authors.forename: Howard H
authors.initials: HH
authors.lastname: Carter
authors.forename: Angela L
authors.initials: AL
authors.lastname: Spence
authors.forename: Ceri L
authors.initials: CL
authors.lastname: Atkinson
authors.forename: Christopher J A
authors.initials: CJ
authors.lastname: Pugh
authors.forename: N Timothy
authors.initials: NT
authors.lastname: Cable
authors.forename: Dick H J
authors.initials: DH
authors.lastname: Thijssen
authors.forename: Louise H
authors.initials: LH
authors.lastname: Naylor
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Green
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001833:Body Temperature Regulation; D005542:Forearm / Q000098:blood supply; D006358:Hot Temperature; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D008833:Microcirculation; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D014664:Vasodilation; D055815:Young Adult