Final answer:
An increase in peripheral resistance is not a mechanism that assists venous return; rather, the skeletal muscle pump, gravity, and heart-generated pressure support this function.
Step-by-step explanation:
The mechanism that does NOT assist in venous return is c) An increase in peripheral resistance. Mechanisms that assist venous return include the skeletal muscle pump, where contraction of muscles during physical activities like walking or running compresses veins and propels blood toward the heart. Another mechanism is the role of gravity in aiding blood flow from the upper body to the heart. Additionally, pressure generated by the heart during relaxation (diastole) creates a lower pressure in the atria than in the veins, facilitating the return of blood to the heart. However, an increase in peripheral resistance usually refers to constriction of blood vessels, which increases blood pressure rather than directly assisting venous return.
In essence, the skeletal muscle pump increases blood pressure within veins due to the compression caused by musculoskeletal contraction, which, along with one-way valves within veins, prevents backflow and helps in maintaining a pressure gradient that favors venous return to the heart. The presence of one-way valves and the use of the skeletal muscle and respiratory pumps contribute to increased venous flow making the skeletal muscle pump essential for this process.