Daily Passive Muscle Stretching Improves Flow-Mediated Dilation of Popliteal Artery and 6-minute Walk Test in Elderly Patients with Stable Symptomatic Peripheral Artery Disease

Background: Patients with peripheral arterial disease (PAD) often have walking impairment due to insufficient oxygen supply to skeletal muscle. In aged rats, we have shown that daily stretching of calf muscles improves endothelium-dependent dilation of arterioles from the soleus muscle and increases capillarity and muscle blood flow during exercise. Therefore, we hypothesized that daily muscle stretching of calf muscles would improve endothelium-dependent vasodilation of the popliteal artery and walking function in PAD patients. Methods: We performed a randomized, non-blinded, crossover study whereby 13 patients with stable symptomatic PAD were randomized to undergo either 4 weeks of passive calf muscle stretching (ankle dorsiflexion applied 30 min/d, 5 days/wk) followed by 4 weeks of no muscle stretching and vice versa. Endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin-induced dilation of the popliteal artery and 6 minute walk test (6MWT) were evaluated at baseline and after each 4 week interval. Results: After 4 weeks of muscle stretching, FMD and 6MWT improved significantly in the muscle stretching group vs. the control (FMD: 5.1 +/- 0.5% vs. 3.7 +/- 0.3%, P = 0.005: 6MWT continuous walking distance: 304 +/- 43 m vs. 182 +/- 34 m: P = 0.0006). No difference in nitroglycerin-induced dilation was found between groups (10.9 +/- 1.2 vs. 9.9 +/- 0.4%, P = 0.48). Post-stretching, 6MWT total walking distance was positively correlated with normalized FMD (R = 0.645, P = 0.02). Conclusions: Passive calf muscle stretching enhanced vascular endothelial function and improved walking function in elderly patients with stable symptomatic PAD. These findings merit further investigation in a prospective randomized trial. (C) 2019 Elsevier Inc. All rights reserved.