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Background: Muscle strain injuries in the human calf muscles are frequent sports injuries with high recurrence. Potential structural and functional changes in the medial head of the musculus gastrocnemius (GM) and the associated aponeurosis are not well documented. Purpose: To test whether a GM muscle strain injury affects muscle fascicle length, pennation angle, and the morphology of the deep aponeurosis at rest and during muscle contraction long time after the injury. Additionally, electromyography (EMG) of the GM and the soleus muscle during a unilateral heel rise was measured in the injured and uninjured calf. Methods: GM fascicle length, pennation angle, and aponeurosis thickness was analyzed on dynamic ultrasonography (US) recordings in 10 participants with a chronic calf strain. In addition, US images taken across the distal portion and mid‐belly of the GM were analyzed at three different ankle positions. EMG recordings were obtained during a unilateral heel rise. Results: The pennation angle of the injured distal GM was significantly larger compared to the uninjured GM in the contracted, but not the relaxed state. Pennation angle increased more in the injured compared to the uninjured GM during contraction. Fascicle length was shorter in the most distal portion of the injured GM. Fascicles at the distal portion of the injured GM showed a pronounced curvilinear shape as the muscle contracted and the aponeurosis was enlarged in the injured compared to the uninjured GM. The ratio between GM and soleus EMG activity showed a significantly higher relative soleus activity in the injured compared to the healthy calf. Conclusion: The greater change in pennation angle and curvilinear fascicle shape during contraction suggest that a long‐term consequence after a muscle strain injury is that some muscle fibers at the distal GM are not actively engaged. The significantly enlarged aponeurosis indicates a substantial and long‐lasting connective tissue involvement following strain injuries. [ABSTRACT FROM AUTHOR]

The myotendinous junction (MTJ) is structurally specialized to transmit force. The highly folded muscle membrane at the MTJ increases the contact area between muscle and tendon and potentially the load tolerance of the MTJ. Muscles with a high content of type II fibers are more often subject to strain injury compared with muscles with type I fibers. It is hypothesized that this is explained by a smaller interface area of MTJ in type II compared with type I muscle fibers. The aim was to investigate by confocal microscopy whether there is difference in the surface area at the MTJ between type I and II muscle fibers. Individual muscle fibers with an intact MTJ were isolated by microscopic dissection in samples from human semitendinosus, and they were labeled with antibodies against collagen XXII (indicating MTJ) and type I myosin (MHCI). Using a spinning disc confocal microscope, the MTJ from each fiber was scanned and subsequently reconstructed to a 3D‐model. The interface area between muscle and tendon was calculated in type I and II fibers from these reconstructions. The MTJ was analyzed in 314 muscle fibers. Type I muscle fibers had a 22% larger MTJ interface area compared with type II fibers (p < 0.05), also when the area was normalized to fiber diameter. By the new method, it was possible to analyze the structure of the MTJ from a large number of human muscle fibers. The finding that the interface area between muscle and tendon is higher in type I compared with type II fibers suggests that type II fibers are less resistant to strain and therefore more susceptible to injury. [ABSTRACT FROM AUTHOR]

Achilles tendinopathy is among the most frequent tendon injuries in sport. Despite evidence‐based management, a significant proportion of patients continue to experience symptoms. This is the first randomized trial to investigate the effect of tendoscopic treatment of midportion Achilles tendinopathy compared with placebo at baseline, 3, 6 and 12 months. Patients with midportion Achilles tendinopathy (non‐responsive to more than 6 months of nonsurgical treatments) were randomly assigned to receive either tendoscopic peritendon shaving or placebo tendoscopic treatment. The primary outcome measure was the total score of the Victorian Institute of Sport Assessment Achilles (VISA‐A) questionnaire. Due to three adverse events (sural nerve injuries), in the group receiving tendoscopic treatment, the trial was stopped short of the planned 48 participants. All 23 patients included completed 3 months' follow‐up (100%), 22 (96%) 6 months' and 19 (83%) completed 12 months' follow‐up. The between‐group estimates favored endoscopic treatment and ranged from 19 points (95% confidence interval [CI]: 1–38) at 3 months, 14 points (−7 to 34) at 6 months and 5 points (95% CI: −19 to 28) at 12 months. After 12 months, the tendoscopic group improved 47 points (95% CI: 29–65) versus 40 points (95% CI: 22–57) in the placebo‐operated group. Despite a smaller sample size due to adverse events, VISA‐A indicate faster recovery from tendoscopic treatment compared to placebo. These data suggest that tendoscopic treatment of midportion Achilles tendinopathy should be tested in further research; however, the technique needs to be refined to avoid sural nerve injuries. [ABSTRACT FROM AUTHOR]