Cutaneous vascular responses to isometric handgrip exercise

Cutaneous vascular responses to dynamic exercise have been well characterized, but it is not known whether that response pattern applies to isometric handgrip exercise. We examined cutaneous vascular responses to isometric handgrip and dynamic leg exercise in five supine men. Skin blood flow was measured by laser-Doppler velocimetry and expressed as laser-Doppler flow (LDF). Arterial blood pressure was measured noninvasively once each minute. Cutaneous vascular conductance (CVC) was calculated as LDF/mean arterial pressure. LDF and CVC responses were measured at the forearm and chest during two 3-min periods of isometric handgrip at 30% of maximum voluntary contraction and expressed as percent changes from the preexercise levels. The skin was normothermic (32°C) for the first period of handgrip and was locally warmed to 39°C for the second handgrip. Finally, responses were observed during 5 min of dynamic two-leg bicycle exercise (150-175 W) at a local skin temperature of 39°C. Arm LDF increased 24.5 ± 18.9% during isometric handgrip in normothermia and 64.8 ± 14.1% during isometric handgrip at 39°C (P < 0.05). Arm CVC did not significantly change at 32°C but significantly increased 18.1 ± 6.5% during isometric handgrip at 39°C (P < 0.05). Arm LDF decreased 12.2 ± 7.9% during dynamic exercise at 39°C, whereas arm CVC fell by 35.3 ± 4.6% (in each case P < 0.05). Chest LDF and CVC showed similar responses. We conclude that skin blood-flow increases during isometric handgrip in contrast to the cutaneous vasoconstriction seen with the onset of dynamic exercise. At 39°C, the increase in skin blood flow is in part due to increased CVC.