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

Abstract

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.

Positional differences in reactive hyperemia provide insight into initial phase of exercise hyperemia

“…The rationale for this study was that the primary evidence for a muscle pump effect in exercise hyperemia comes from results of experiments which have demonstrated that limb position influences the blood flow response to muscle contraction (12,22,25,31,36). We reasoned that a critical control experiment has been lacking, i.e., testing whether the response to vascular challenges other than contraction elicit positional differences in blood flow.…”

“…Because of technical limitations, it has not been feasible to perform experiments to directly test this hypothesis, yet the idea has persisted despite the lack of direct confirmation. Data from studies showing a greater blood flow response to muscle contractions when the limb is in the dependent position (12,22,25,31,36) have been the primary evidence for a skeletal muscle pump contribution to exercise hyperemia. We have argued previously that the magnitude of contraction-elicited changes in blood flow is far greater than can be accounted for by putative changes in intravascular pressure (38) and that the time course of changes in blood flow does not correlate with that predicted from the muscle pump (4).…”

“…The best evidence supporting the muscle pump is the greater blood flow response to muscle contractions when the limb is below the heart, when veins should be full due to gravity, compared with the above heart position when veins are empty (e.g., Refs. 12,22,25,31,36).On the other hand, a number of studies over the last decade have provided evidence that muscle contraction causes rapid vasodilation. Experiments performed using the hamster cremaster (2, 24) or retractor muscles (39) demonstrate that muscle contraction causes vasodilation of arterioles within 2-3 s of the onset of muscle contraction.…”

“…The best evidence supporting the muscle pump is the greater blood flow response to muscle contractions when the limb is below the heart, when veins should be full due to gravity, compared with the above heart position when veins are empty (e.g., Refs. 12,22,25,31,36).…”

Fascia Research II: Second International Fascia Research Congress

“…Not noted by Purslow is another function of this layer: these normal pressure changes result in cyclical changes throughout the gait cycle, which assists in venous return of blood to the heart, with the calf muscles serving as a "second heart pump" (18,19) and assisting with perfusion to the muscle itself. (20) Furthermore, the arteriolar dilation previously noted by Hocking (10) may further contribute to this muscle pumping mechanism.…”