Sustained Skeletal Muscle Blood Flow Elevations Following Prolonged Passive Leg Movement

Abstract

Passive limb movement results in up to a threefold increase in skeletal muscle blood flow following movement. The increased blood flow occurs independently of local tissue metabolism, but is likely related to changing sheer patterns from mechanically‐induced blood flow, tissue distortion, and afferent feedback from group III/IV nerves. Prior research suggests that following acute bouts of passive limb movement, blood flow is only elevated transiently, and returns to baseline within minutes. Whether increased duration of passive movement could extend the duration of increased blood flow after movement, generating a sustained elevation in skeletal muscle blood flow that is similar to sustained postexercise vasodilation, is unknown. However, if passive movement can elicit a sustained vasodilation, the underlying mechanisms could contribute to the sustained postexercise vasodilation. Therefore, the purpose of this experiment was to determine the duration of elevated skeletal muscle blood flow in response to an extended duration (60 min) of passive movement. It was hypothesized that 60 min of passive leg movement would increase skeletal muscle blood flow for up to 60 min following movement. Four young, healthy, recreationally active individuals (3M, 1F) volunteered for this study. Limb blood flow and muscle perfusion were assessed in the supine position in both the right (Passive) and left (Control) legs 30 min prior to and 60 min following passive movement. Limb blood flow was estimated via Doppler ultrasound at the femoral artery, and muscle perfusion was estimated in the vastus lateralis using the near‐infrared spectroscopy response to intravenous infusion of indocyanine green (IC‐Green, Akorn). Passive movement of the volunteer's right leg (Passive) consisted of knee flexion from 45 to 90 degrees, completed at a cadence of 45 flexions per min for 60 min. To confirm limb movement was passive, muscle activity was monitored via surface electromyography. Heart rate and blood pressure were recorded throughout the study by electrocardiogram and an automatic acoustic sphygmomanometer. At 60‐min following passive movement, limb blood flow tended to remain elevated in the Passive leg (25.5±6.4% P=0.06), but not in the Control leg (+9.1±5.4%, P=0.22) when compared to pre‐movement measures. Additionally, at 60‐min after passive movement, limb blood flow tended to be higher in Passive leg than in Control (P=0.09). Alternatively, muscle perfusion was elevated in the Passive leg (50.2±7.8%, P=0.03) and tended to be elevated in the Control leg (39.7±6.1%, P=0.09) at 60‐min following movement compared to pre‐movement measures, and did not differ between the Passive and the Control legs (P=0.62). Heart rate and blood pressure did not change from baseline, to passive movement, and during recovery from movement. These results indicated that prolonged passive movement can cause a sustained elevation in skeletal muscle blood flow in the moved limb, but may have broader impacts on microvascular perfusion. We suggest that the underlying mechanism(s) for this response, which remain to be identified, could contribute to the sustained postexercise vasodilation.Support or Funding InformationSupport provided by NIH grant HL115027This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.