Static Muscle Stretching Enhances Vascular Responsiveness of the Tibial Nutrient Artery

Abstract

The magnitude of bone formation and remodeling is linked to both the magnitude of strain placed on the bone and the perfusion of bone. We have previously shown that daily static stretching of the ankle flexor muscles in aged rats results in increased blood flow to the stretched muscles and to the proximal tibial metaphasis during walking exercise. The purpose of this study was to determine the effects of daily static muscle stretching on vasoreactivity of the nutrient artery that perfuses the proximal tibial metaphasis. Static stretching of ankle flexor muscles was performed in aged male Fischer 344 rats (20 months) by placement of a dorsiflexion splint on the left ankle for 30 min/day, 5d/wk for 4wks. The right hindlimb served as a contralateral control (unstretched) limb. After the 4 wk stretching intervention, the tibial nutrient artery was isolated from both the stretched and unstretched limb. Vasoconstrictor responses to the adrenergic agonist, phenylephrine (10‐9‐10‐4M) and vasodilatory responses to acetylcholine (10‐9‐10‐4M) and Dea‐NONO‐ate (10‐9‐10‐4M) were evaluated. Vasoconstrictor responses to phenylephrine were significantly increased in the tibial nutrient artery from the stretched limb as compared to those from the unstretched limb (maximal constriction, stretched limb = 54±4%, maximal constriction, unstretched limb = 42±6%; P<0.05 stretched vs. unstretched). Endothelium‐dependent vasodilation to acetylcholine was also significantly increased in the tibial nutrient artery from the stretched limb (maximal dilation = 62±5%) as compared to the unstretched limb (maximal dilation = 41±5%); P<0.01, stretched vs. unstretched). Endothelium‐independent dilation to the NO donor, Dea‐NONO‐ate was not different in the tibial nutrient arteries from the stretched and unstretched limbs. These data indicate that static muscle stretching alters the reactivity of both the smooth muscle and the endothelium of the tibial nutrient artery, leading to enhanced vasoconstrictor and vasodilatory responsiveness of the artery. This enhancement of vascular function in the nutrient artery may contribute to increased perfusion of the tibia during walking exercise following 4 weeks of daily static stretching.Support or Funding InformationSupported By: NIH R15AG055029