PURPOSE: Passive limb movement results in an immediate transient increase in blood flow to the limb that returns to baseline within 45-60 seconds. The efficacy of passive limb movement to increase tissue perfusion and maintain vascular health in bed ridden and spinal cord injured (SCI) individuals, therefore, will depend on whether repeated bouts of passive limb movement yield the same hyperemic response. Thus, the purpose of this investigation was to determine the cardiovascular responses to repeated bouts of passive limb movement.
METHODS: Fifteen college aged individuals (7 male, 8 female) participated in two protocols in which five 1 minute bouts of passive knee extension/flexion were separated by either 1 or 3 minutes of recovery. To help maintain consistent range of motion a knee brace and electronic goniometer were placed on the moving leg. Femoral blood flow, heart rate (HR) and mean arterial pressure (MAP) were recorded and conductance calculated for 30 second baseline periods and at 3 second intervals through all bouts of passive knee movement.
RESULTS: There was a significant increase in femoral blood flow during each bout of passive limb movement whether it was separated by 1 or 3 minutes of recovery (P<0.05). With one minute recovery the absolute and relative increase in femoral blood flow was 225.4 ml/min (141.8%), 153.2 ml/min (81.8%), 220.1 ml/min (133.0%), 193.6 ml/min (120.9%) and 200.6 ml/min (130.3%) across the 5 bouts, respectively. With 3 minute recovery period the absolute and relative increase in femoral blood flow was similar: 333.6 ml/min (183.65%), 174.0 ml/min (99.9%), 286.6 ml/min (157.9%), 232.0 ml/min (119.0%) and 275.0 ml/min (157.1%) across the 5 bouts, respectively. These hyperemic responses resulted from consistent increases in HR (approximately 5.0%) and MAP (approximately 5.0%) across the trials.
CONCLUSIONS: Based on these data, repeated bouts of passive limb movement results in a consistent hyperemic response with recovery periods as short as 1 minute. Thus repeated passive limb movement may serve as an exercise modality to periodically increase blood flow and tissue perfusion to the lower limbs of bed ridden and SCI individuals.