What are both lymph and venous blood flow heavily dependent on?

Lymph flow is highly dependent on the contraction of skeletal muscles and pressure alterations during breathing. Similarly, venous blood flow relies on breathing movements and contraction of skeletal muscles, "Hole’s Human Anatomy and Physiology" explains.

Contracting skeletal muscles exert pressure on veins, helping pump blood from one valve to another. Differences in thoracic pressure act in conjunction with skeletal muscle movements to accelerate the flow of venous blood to the heart. Lymphatic vessels have one-way valves inside them, which permit lymph flow in only one direction. The lymphatic system and the venous vessels use similar processes to control the flow of fluid.