Deterioration of venous function in normal lower extremities during daily activity.

The change in venous function during the course of the day was studied noninvasively in 50 normal lower extremities of 25 physically active normal subjects. Venous refilling time, measured by photoplethysmography, was significantly shorter (p less than 0.0001), and venous capacitance, measured by impedance plethysmography, was significantly reduced (p less than 0.04) after 5 hours or more of daily activities performed in the upright position. Abnormally short venous refilling time (less than 18 seconds) developed in 21% of the extremities, which had a normal venous refilling time earlier in the same day. Lower extremity symptoms of ache, pain, or swelling were reported more frequently in extremities that developed an abnormal venous refilling time. There was a trend toward a greater change in venous refilling time during the day in symptomatic lower extremities than in asymptomatic limbs (p = 0.07).