Relative contraction force producing a reduction in calf blood flow by superimposing forearm exercise on lower leg exercise.

The relative contraction force producing a reduction in exercise hyperaemia was studied by superimposing handgrip contraction at different intensities on plantar flexion of low intensity. Ten active women served as subjects. Blood flow to the forearm (Qforearm) and calf (Qcalf) was measured with mercury-in-rubber strain gauges by venous occlusion plethysmography immediately after 60 s of rhythmic plantar flexion at 10% of maximum voluntary contraction (MVC), which was expressed as P10H0, or combined plantar flexion and handgrip contraction. In the combined exercise, handgrip exercise at 30%, 50% or 70% MVC was added to plantar flexion during the last 30 s of exercise (P10H30, P10H50 and P10H70, respectively). The Qforearm increases after P10H30, P10H50 and P10H70 were significantly larger (P < 0.01) than that after P10H0, and the difference between P10H30 and P10H70 was also significant (P < 0.01). Immediate post-exercise Qcalf after P10H0 increased by 7.4 (SEM 0.9) ml x 100 ml-1 x min-1. When handgrip contraction at 70% MVC was added, the Qcalf increase after exercise [4.5 (SEM 0.7) ml x 100 ml-1 x min-1] was significantly lower than after plantar flexion alone (P < 0.05). However, no significant change was found in Qcalf when the forces of added handgrip contraction were 30% and 50% MVC, although the mean value of Qcalf increase was lower after P10H50 combined exercise. Calf vascular resistance calculated as BP/Qcalf (BP mean blood pressure) tended to increase after P10H70 to a nonsignificant extent. Heart rate and oxygen uptake in these exercises increased when handgrip contraction at 30%, 50%, or 70% MVC was added to plantar flexion at 10% MVC.(ABSTRACT TRUNCATED AT 250 WORDS)