Relative effects of static muscle contraction on digital artery and nailfold capillary blood flow velocities.

Previous studies have shown that a decrease in blood flow to the finger is not necessarily accompanied by a corresponding change of blood flow in nailfold capillaries. The purpose of this study was to determine if nailfold capillary blood flow remains relatively stable during a decrease in finger blood flow induced by muscle contractions. Four male subjects 20 to 30 years of age exerted 2-min periods of static calf muscle contraction at levels of 7.5, 15, 30, and 45% of their maximum voluntary contractile force (MVC) while systemic blood pressure (BP), and flow velocities in the digital artery (VEL-A) and nailfold capillaries (VEL-C) were measured by, respectively, Doppler ultrasound and video densitometry. Each subject repeated the series five times. There was a significant linear decrease in VEL-A with increasing force of contraction for each subject individually (P less than or equal to 0.009) and for the group as a whole (P less than or equal to 0.0001); whereas VEL-C did not significantly change during muscle contraction. These results indicate that the initial cutaneous constrictor response in the finger during the onset of leg muscle exercise is not reflected to the nailfold capillaries.