Stretching denervated muscle does not prevent atrophy, but it increases fibrosis via temporal modulation of TGF-β1/myostatin and MMP-9 cascades.

This review demonstrated little evidence with poor to fair quality on the structural muscle adaptations in the poststroke subjects, showing muscle atrophy, a higher stiffness, and amount of fibrous and fat tissue without alterations in lean tissue of distal muscles of the paretic UL compared to the nonparetic limb. However, the nonparetic side also presented alterations, which makes it an inappropriate comparison. Thus, well-designed studies addressing this issue are required.

Introduction Upper limb movements are affected frequently by brain ischemia (BI). Mechanisms involved in recovery and compensatory movements have developed several studies. However, less attention is given to skeletal muscles, where neuromuscular junction (NMJ) has an important role on muscle tropism and functional performance. Methods Animals were divided into two groups: control (C) and BI. Then, animals were skilled to perform single‐pellet retrieval task, following these procedures: habituation, shaping, and single‐pellet retrieval task. BI was induced using stereotaxic surgery in order to apply endothelin‐1 in motor cortex, representative of movements of dominant paw. Reaching task performance was evaluated by single‐pellet retrieval task 1 day before BI induction, 4 and 15 days after BI induction. After that, biceps, triceps, fingers flexor, and extensor muscles were extracted. NMJ was assessed in morphometric characteristics (total area, total perimeter, and feret). Muscle fiber cross‐sectional area and connective tissue percentage were also evaluated for characterization. Student's t test was used for comparisons between C and BI groups. Tau Kendall's correlation was applied among variables from BI group. Results An increase in all NMJ morphometric parameters, as well as increase of atrophy and fibrosis in BI group compared with C. There was a high level of direct correlation between mean values of NMJ morphometry with percentage of success in reaching task in BI group. Conclusion Brain ischemia‐induced NMJ compensatory expansion, muscle atrophy, and fibrosis in forelimb muscles that are related to reaching performance.