Exhausting handgrip exercise reduces the blood flow in the active calf muscle exercising at low intensity

The calf and forearm blood flows (Qcalf and Qforearm respectively), blood pressure, heart rate and oxygen uptake of six men and women were studied during combined leg and handgrip exercise to determine whether a reduction of exercise-induced hyperaemia would occur in the active leg when exhausting rhythmic handgrip exercise at 50% maximal voluntary contraction (MVC) was superimposed upon rhythmic plantar flexion lasting for 10 min at 10% MVC (P10) prior to this combined exercise. The Qcalf and Qforearm were measured by venous occlusion plethysmography during 5-s rests interposed during every minute of P10 exercise and immediately after combined exercise. The muscle sympathetic nerve activity (MSNA) changes were also recorded during leg exercise alone and combined exercise. During plantar flexion performed 60 times.min-1 with a load equal to 10% MVC (P10), Qcalf was maintained at a constant level, which was significantly higher than the resting value (P < 0.001). When rhythmic handgrip contraction at 50% MVC (H50) and P10 were performed simultaneously, the combined exercise was concluded due to forearm exhaustion after a mean of 51.2 (SEM 5.5) s. At exhaustion, Qcalf had decreased significantly from 20.6 (SEM 3.0) ml.100 ml-1.min-1 (10th min during P10 exercise) to 15.3 (SEM) ml.100 ml-1.min-1 (P = 0.001), whereas Qforearm had increased significantly (0.001 < P < 0.01) from 8.6 (SEM 1.9) ml.100 ml-1.min-1 (10th min of P10 exercise) to 26.2 (SEM 3.2) ml.100 ml-1.min-1. The mean blood pressure remained at an almost constant level during the 3rd to 10th min of P10 exercise and increased markedly when H50 was added.(ABSTRACT TRUNCATED AT 250 WORDS)