Blood flow increases during exercise primarily due to the increased demands of working muscles, leading to several physiological changes. One key factor is the rhythmic contractions of muscles, which have a mechanical effect on blood vessels.
Specifically, the increase in blood flow is significantly influenced by:
- Increased Extravascular Pressure: Rhythmic muscle contractions create increased extravascular pressure. This pressure essentially squeezes the blood vessels.
- Venous System Expulsion: The increased pressure expels blood through the venous system. This action is similar to how squeezing a tube of toothpaste forces the contents out.
- Arterio-Venous Pressure Gradient: The expulsion of blood through the veins increases the pressure difference between the arteries and veins (the arterio-venous pressure gradient). According to referenced research [34, 92, 119, 180, 367, 525, 613, 628], this increased pressure gradient makes it easier for blood to flow from the arteries, where the pressure is high, to the veins, where the pressure is lower. This facilitates a greater volume of blood moving through the muscles.
In summary, the mechanical action of contracting muscles significantly contributes to the increased blood flow observed during exercise by squeezing blood through the veins and enhancing the pressure gradient that drives blood circulation.
