Effect of the leg muscle pump on the rise in muscle perfusion during muscle work in humans.

The transient and steady-state effects of the calf muscle pump on the rise in muscle perfusion during rhythmic plantarflexions were investigated in 20 volunteers. Because a large hydrostatic column would increase the effect of a muscle pump, exercise in the supine and head-up tilted positions was compared. Within approximately 15 s of the start of muscle work, femoral artery flow (ultrasound Doppler) rose 0.37 L/min above rest in the supine and 0.5 L/min above rest in the tilted position. The latter is a significantly larger rise (P < 0.05). After 80 s of muscle work, femoral flow was stable at 0.38 and 0.39 L/min above rest in the supine and tilted positions, respectively. We conclude that the muscle pump contributes to muscle perfusion during the initial phase of muscle work, but that metabolic vasodilation is a more important determinant of muscle perfusion during steady-state muscle work.