THE PERIPHERAL PUMP
While the heart is the key pump in the central unit, pumping blood into the lungs and also arteries, the peripheral pump is equally important for ensuring venous blood flow back to the heart. Essentially the heart can only pump the volume of blood that it receives from venous return, so the peripheral pump plays an integral role.
Although the heart is stronger as a pump, it has to be due the higher TPR experienced in the arterial circuit. Peripherally the venous circuit has a lower resistance and as such does not require the same pumping power.
The peripheral pump refers to the effect of the contracting muscles on the venous circuit. As the muscles contract they compress the vessels in the venous circuit pushing the blood back towards the heart. An effective peripheral pump is critical in maintaining diastolic blood pressure (flow back to the heart).
At rest the venous pressure is 90-100mm Hg, due to the effects of gravity opposing venous return. The onset of exercise causes the muscles to squeeze blood through the veins and reducing the pressure in the venous circuit well below the resting 90-100mmHg. This pumping action greatly assists the return of blood and helps take the load of the heart.
The peripheral pump is improved with faster movement speeds, for example pedaling or running with higher cadence. At higher cadences the amount of muscle force required is lower, arterial TPR is optimised and there is greater facilitation of venous return enabling more oxygen, nutrient and waste transfer.
The technique you employ will determine the frequency and force of contraction, affecting the venous return and maximum blood flow. This in turn will determine your exercise capacity.
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