Attenuation of the cutaneous blood flow response during combined exercise and heat stress.
Skin blood flow (SkBF) was measured in six male subjects using laser-Doppler velocimetry, with zero-gradient auditory canal temperature (Tac) used as an index of body core temperature (Tc). Subjects performed incremental, upright cycling commencing at 40% peak power (Wpeak: 10 min), increasing every 4 min by 5% Wpeak thereafter. Trials were conducted in hot (ambient temperature (Ta) 36.7 +/- 0.2 degree C, relative humidity (rh) 46.1 +/- 3.2%; mean +/- S.D.), and neutral environments (Ta 19.6 +/- 0.3 degree C, rh 50.2 +/- 1.4%). SkBF increased with Tac in all subjects. Attenuation of SkBF occurred at the same Tac, relative SkBF and cardiac frequency (fc) between environments, but at a lower exercise intensity (40.8 +/- 0.8% versus 55.8 +/- 3.0% Wpeak) in the hot environment (p < 0.05). Data indicate that Tc thresholds for SkBF attenuation may exist. However, it is suggested that attenuation thresholds coincided with a reduced central blood volume, which may occur at a critical level of cutaneous blood pooling.
Department of Biomedical Science, University of Wollongong, Australia.
M J
MJ
Patterson
D
D
Warlters
N A
NA
Taylor
D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure; D001831:Body Temperature; D002302:Cardiac Output; D015444:Exercise / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D012879:Skin Physiological Phenomena; D013312:Stress, Physiological / Q000503:physiopathology*; D014664:Vasodilation