Effect of long-term passive stretching of the knee extensor and plantar flexor muscles on vascular function

During each single bout of passive stretching (PS), blood flow (BF) in the feeding artery of the muscle involved in the maneuver decreases, then increasing during relaxation. These PS-induced BF changes may improve vascular function after long-term PS administration due to repetitive stimuli applied to the artery’s wall. To this purpose, 36 participants (age: 23±2 yrs; stature: 1.68±0.12 m; body mass: 62±15 kg) were randomly assigned to PS (n=18; 6 wks, 5 times/w) or control group (CTRL, n=18). Before and after PS of the knee extensor and plantar flexor muscles or after a similar resting period in CTRL, vascular functionality of the arteries directly involved in (femoral and popliteal arteries) and distal to (brachial artery) PS administration was assessed by duplex eco-doppler. Single passive limb movement (SPLM) assessed the femoral artery BF changes. Flow mediated dilation (FMD) tested the popliteal and brachial arteries. SPLM peak BF (BFp) and maximum arterial vasodilation (FMD%) were calculated. Pulse-wave velocity (PWV) was determined by tonometry to quantify central (carotid-femoral artery PWV, PWVCF) and peripheral (carotid-radial artery PWV, PWVCR) arterial stiffness. Systolic (SBP) and diastolic (DBP) blood pressure were also measured. In PS, BFp and popliteal FMD% increased after PS by 30% and 25%, respectively (p<0.05). Brachial FMD% increased by 8% (p<0.05). PWFCF and PWVCR decreased by 10% and 7%, respectively (p<0.05). No changes in SBP and DBP occurred. CTRL did not show any significant alteration. Six weeks of PS intervention improved vascular function and reduced arterial stiffness, particularly in the feeding arteries of the muscles involved in PS. Therefore, PS could be used as an effective means to passively improve vascular functionality.