Effect of local exercise of forearm muscles on forearm capacitance vessels

Normal subjects were studied to determine whether exercise of the muscles of one forearm causes changes in venous tone in that forearm by some local mechanism. Forearm venous pressure-volume relationships and the pressure in “isolated” vein segments were unchanged after exercise of forearm muscles. Following venous occlusion, the forearm volume increases and reaches a plateau later than forearm venous pressure. This delayed volume change increased with increasing venous filling rate regardless of whether this was accomplished by exercise or by other means. Thus, the local mechanism which dilates resistance vessels in active muscles does not seem to change the contractile state of the muscle in the capacity vessels. The viscous properties of the venous wall, however, act to damp the volume oscillations in intervals between muscular contractions when arterial inflow and venous filling rate are high. The ratio between initial rate of rise in forearm venous pressure and volume following venous occlusion could not be used as an index of active changes in tension of the smooth muscle of the capacitance vessels. strain-gauge plethysmography; isolated vein segments; venous response to varying filling rates; venous response to local exercise; veins and exercise Submitted on November 16, 1964