Thigh Muscle Pump Function During Ambulation.

It is generally accepted that blood flow in the superficial venous system of the lower extremity is anterograde whether the body is at rest (lying, sitting, or standing) or in motion (walking). However, it has been shown that during locomotion, anterograde blood flow in the superficial veins from the calf to the thigh was not observed. Instead, the blood flowed towards the intramuscular veins of the lower leg. The purpose of this study was to determine the pressure gradient directing the blood flow in the thigh venous network during ambulation. Sixteen healthy volunteers (legs) were enrolled in the study. Venous pressure was measured in the great saphenous vein (GSV) at the upper and distal thigh and in the intermuscular vein of the posterior thigh during treadmill walking at 30, 45 and 60 stride cycles min-1. The blood flow rate in the common femoral artery (LBF, L/min) was measured by duplex ultrasound at rest and immediately following each exercise test. Fourteen lower extremities were included in the analysis, two were excluded due to technical failure. A pressure gradient (PG) directed from the superficial to the intermuscular vein (Sv-Iv) was observed for the majority the stride cycle time. The magnitude of the Sv-Iv PG was found to be considerably higher than the pressure gradient observed between knee and groin GSV levels. The GSV pressure averaged over the cycle time (P̅, mmHg), was found to be similar at the knee and groin levels, irrespective of walking frequency. During natural ambulation, the resulting pressure gradient was directed from superficial to intermuscular veins for the majority of the stride cycle time. The thigh muscle pump functions as a flow diverter pump, redirecting blood flow from the superficial to the intramuscular venous networks via perforating veins.