Differential effects of isometric exercise on the cutaneous circulation of different regions.

Studies have been made in healthy human subjects of the changes evoked by isometric hand grip in arterial pressure, heart rate and cutaneous red cell flux, the latter being recorded using a laser Doppler meter. Hand grip for 2 min evoked increases in arterial pressure and heart rate, the magnitude of which were graded with the force of contraction (75, 50, or 25% maximum voluntary contraction). Cutaneous red cell flux in the contralateral forearm decreased significantly during 25 and 50% maximum voluntary contraction, while the cutaneous vascular resistance (arterial pressure/cutaneous red cell flux) increased to extents that were graded with the maximum voluntary contraction, indicating graded vasoconstriction. By contrast, cutaneous red cell flux in the face tended to increase, this reaching significance at 75% maximum voluntary contraction. Cutaneous vascular resistance in the face increased in some subjects, but decreased in others, vasodilator responses being most common during 75% maximum voluntary contraction when sweating commonly appeared on the face. In the dorsum of the foot, red cell flux did not change during 75% maximum voluntary contraction, although foot cutaneous vascular resistance increased significantly by the end of the first minute of contraction. At 50 and 25% maximum voluntary contraction most subjects showed an increase in foot cutaneous vascular resistance, but the remainder showed a decrease. We propose that isometric hand grip causes vasoconstriction in the cutaneous circulation of the contralateral forearm, the face and foot, that this response is strongest in the forearm and weakest in the face, and that in the face and foot, the vasoconstriction may be overcome by vasodilatation secondary to sweating.