Central command and muscle metaboreflex effect on superficial venoconstriction in the resting limb

Exercise significantly activates the sympathetic nervous system. Sympathetic activation during exercise is governed by both central command and muscle reflex mechanisms (i.e., muscle metabo- and mechano-reflexes), which modulate arterial vascular responses to exercise. Although many studies have reported that exercise causes sympathetic venoconstriction, none have investigated whether both central command and muscle reflex mechanisms also contribute to regulate venous vascular responses to exercise. Therefore, using ultrasound technique, we assessed changes in the cross-sectional area of the superficial vein in the resting limb as an index of venoconstriction during static exercise with and without tendon vibration, and during the post-exercise recovery period with and without muscle ischemia. We found that both central command and the muscle metaboreflex play an important role in regulating the venous vascular system as observed in the arterial vascular system.