Venous return, the process by which blood is circulated back to the heart, is facilitated by a number of factors. These factors include inspiration, increased total blood volume, increased venomotor tone, and activity of skeletal muscles. According to research published in the Journal of Physiology, inspiration, increased venomotor tone, and increased total blood volume are all factors that aid venous return. On the other hand, activity of skeletal muscles is not an aid to venous return.

Inspiration is the act of expanding the lungs, which in turn increases thoracic pressure. This pressure affects the pressure of the veins, which helps to return blood to the heart. Increased venomotor tone is the result of the constriction of veins, which helps to increase the blood pressure within the veins. This also aids with venous return. Increasing the total blood volume helps to improve the heart’s ability to pump blood back to the heart.

Muscle activity does not aid venous return. Movement of skeletal muscles helps to compress veins, which can help to increase the venous pressure, but it also causes the veins to become less constricted, thus reducing the pressure of the venous blood. This ultimately decreases the effectiveness of venous return.

In conclusion, venous return is aided by inspiration, increased total blood volume, increased venomotor tone, but not the activity of skeletal muscles. Therefore, the answer to the statement is “activity of skeletal muscles”.