VASCULAR DENSITY AT THE MYOTENDINOUS JUNCTION OF THE RAT GASTROCNEMIUS-MUSCLE AFTER IMMOBILIZATION AND REMOBILIZATION

Muscle injuries often occur at or near the myotendinous junction. Immo bilization decreases the tensile strength of the myotendinous junction and predisposes it to strain injury. However, there are no data avail able on whether physical training or remobilization can lower the susc eptibility of the myotendinous junction to strain injuries. We investi gated the effects of three different remobilization programs (8 weeks) after immobilization (3 weeks) by evaluating the vascular density at the myotendinous junction of the rat gastrocnemius muscle. The myotend inous junctions had a portal system vascularity, or capillary-arteriol e-capillary system, which probably protects the blood supply against p athologic conditions. The vascular density at the myotendinous junctio n decreased about 30% after immobilization (P < 0.001). After free cag e remobilization for 8 weeks, the mean vascular density returned to th e level of the controls. After progressively increasing running progra ms the vascular density was slightly higher in the immobilized myotend inous junction and about 50% higher than controls in the contralateral myotendinous junction (P < 0.001). The capacity of the vascular bed o f the rat myotendinous junction to recover from immobilization atrophy seems to be good. Progressively increasing physical training improves the process of revascularization and probably protects an injured and immobilized muscle from reinjury.