<p>The Achilles tendon is the thickest and the strongest tendon in the human body. Many studies, investigating biomechanical properties of plantar flexors muscle-tendon unit after ATR surgery, reported an incomplete calf muscle contractile functional recovery. However, these studies only investigated the plantar flexors muscle function failing to provide information about the adaptive changes in motor strategy. In fact, the development of adaptive changes in motor strategies, due to both mechanical and neural factors, may result in pathological musculoskeletal conditions over the long term. Understanding physiological calf muscle changes due to long-term immobilization may help prevent Achilles tendon re-rupture cases.</p>

The primary muscles responsible for plantar flexion movement are soleus and gastrocnemius which connects to the calcaneus by the Achilles tendon. Achilles tendon rupture is managed most often with open surgical repair in which the affected limb is immobilized. Understanding the effects of long-term immobilization, how these lead to changes in the physiological properties of the calf muscles changes, may help to improve rehabilitation. Investigating the biomechanical behavior of the calf muscles may provide a better understanding of how the inferior material properties of a scarred Achilles tendon may influence the more global structural properties of the intact muscles