Stretch-induced adaptations in skeletal muscle microcirculation

Abstract

Skeletal muscle oxygen consumption explosively must increase in response to exercise for the generation of adenosine triphosphate. Skeletal muscle arterioles have a crucial role in regulating vascular resistance, contributing to exercise-induced hyperemia. Endothelial cell, which is lining the inner layer of blood vessels, senses and responds to physical stimuli including shear stress and stretch. Muscle stretching is widely performed in patients who undergo physical therapy. Recent clinical studies showed a favorable vascular adaptation after muscle stretching. However, the mechanism underlying stretch-induced vascular adaptation still remains unclear. The aim of this review is to outline the effect of muscle stretching on vascular endothelial function of human. We also aimed to explain the stretch-induced alteration in skeletal muscle microcirculation from mechanistic point of view. Skeletal muscle blood flow acutely decreased by approximately 50% when muscle was stretched. After a 1-month of daily muscle stretching, exercise-induced hyperemia was significantly enhanced in accordance with improvement of endothelium-dependent vasodilation of arterioles, capillarity, and endothelial nitric oxide synthase and vascular endothelial growth factor expression in stretch-treated muscle. In the elderly patients who had limited walking capacity due to symptomatic peripheral artery disease, muscle stretching improved walking distance and augmented flow-mediated dilation of popliteal artery. Therefore, the enhanced arteriolar responsibility, angiogenesis, and increased exercising blood flow could be possible mechanisms underlying stretching-induced improvement of walking capacity.