Muscle Contraction Is Essential for Tendon Healing and Muscle Function Recovery After Achilles Tendon Rupture and Surgical Repair.

Incomplete tendon healing and postponed muscle weakness after Achilles tendon rupture and surgical repair lead to poor performance in patient activities. Although the effectiveness of postoperative early functional rehabilitation has been proven, the priority and each effect of specific methods in early rehabilitation remain unclear. We hypothesized early muscle contraction exercises without joint motion would promote tendon healing and prevent calf muscle atrophy; in contrast, early static stretching after surgical repair would not contribute to tendon healing and induce calf muscle atrophy. C57Bl/6 mice underwent Achilles tendon rupture and suture repair, followed by different methods of post-surgery interventions: a non-exercise group, a Static stretching group, and an Electrical muscle stimulation group. 3 and 5 weeks after surgery, we assessed ex vivo tendon mechanical properties, collagen fiber alignment, and histological muscle properties. Electrical Muscle Stimulation restored the recovery of tendon mechanical properties and muscle strength more quickly than Static stretching. Static stretching had no additional effect on them compared to the non-exercise. Our results suggested that calf muscle contraction was essential as a post-surgery early functional rehabilitation to load tensile forces on tendons and improve Achilles tendon healing. Additionally, early muscle contractions naturally promote restoring muscle function after the rupture, but further research is needed to optimize muscle contraction protocols.