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The purpose of this study was to evaluate the integrity of the muscle membrane and its associated cytoskeleton after a contraction-induced injury. A single eccentric contraction was performed in vivo on the tibialis anterior (TA) of male Sprague-Dawley rats at 900°/s throughout a 90°-arc of motion. Maximal tetanic tension (P_o) of the TAs was assessed immediately and at 3, 7, and 21 days after the injury. To evaluate sarcolemmal integrity, we used an Evans blue dye (EBD) assay, and to assess structural changes, we used immunofluorescent labeling with antibodies against contractile (myosin, actin), cytoskeletal (α-actinin, desmin, dystrophin, β-spectrin), integral membrane (α- and β-dystroglycan, sarcoglycan), and extracellular (laminin, fibronectin) proteins. Immediately after injury, P₀ was significantly reduced to 4.23 ± 0.22 N, compared with 8.24 ± 1.34 N in noninjured controls, and EBD was detected intracellularly …