Changes in tone of limb veins during supine exercise

Abstract

Normal subjects have been studied to assess the response of the capacitance vessels in the forearm during supine leg exercise. Measurements were made of changes in forearm volume (strain-gauge and water-filled plethysmographs) at a given pressure in the large forearm veins, of changes in pressure in the forearm veins with the circulation to the forearm arrested and in “isolated” vein segments. The results were consistent and demonstrated that exercise with a work load of 270–810 kg/min caused constriction of forearm capacitance vessels via the sympathetic nerves proportional to the severity of the exercise. Venoconstriction also occurred in the hand, and in the calf during arm exercise. Local exercise of the forearm muscles during supine leg exercise, which increased forearm blood flow by dilating the resistance vessels, did not prevent the increase in venous tone in the forearm. Thus a reflex increase in tone in the limb veins, both in the exercising and in the nonexercising parts, contributes to the cardiovascular adaptation to exercise. venoconstriction in exercising and nonexercising limbs; reflex venoconstriction with exercise graded to severity of work; reflex venoconstriction with exercise mediated through sympathetic nerves Submitted on June 15, 1964