Question

How does breathing and other forms of muscular activity contribute to venous blood flow.

Answer 1

Each time your heart beats, your left ventricle contracts and forces blood into your arteries, vessels that deliver oxygen-rich blood to cells throughout your body. In the capillaries at the site of the cell, oxygen is extracted and exchanged for carbon dioxide, an end product of cellular metabolism. The veins then carry the CO2 to the lungs to be expired and replaced with fresh oxygen, a process called venous return. In a healthy heart, this cycle repeats itself perpetually without interruption.

During exercise, the rhythmic pump of your muscles facilitates venous return by forcing blood through the one-way valves that lead to the heart. What's more, increased lung activity creates a change in thoracic pressure that draws blood toward your heart. Regular exercise improves venous return by increasing total blood volume, increasing end diastolic volume, and increasing the size and contractile strength of the heart muscle. Exercise also increases the number of capillaries at the muscle where oxygen and CO2 are exchanged, reducing peripheral resistance.