Muscle- Tendon Unit
The muscle-tendon unit can be broken down into three components which include the muscle itself (contractile element), muscle membranes (parallel element) and tendon (series element). Both the muscle membranes and tendons are connective tissue structures and can be collectively group as the ‘elastic elements’ of the muscle-tendon unit.
When developing force, the contractile element is often the only component that is considered, but the elastic elements are also important. The muscle membranes and, even more so, tendons can store energy and contribute to total force production. Connective tissue structures also undergo physiological adaptations (hypertrophy, stiffness, etc) associated with training just like the muscle tissue.
Each of these components are susceptible to injury and/or pain too. Muscles can be strained and tendons can undergo reactive changes leading to tendinopathy when load surpasses capacity. When it comes to the muscle-tendon unit and injury prevention, the most useful concept to keep in mind is the relationship between load and capacity. Load that surpasses capacity, that is appropriately dosed, can be positive for adaptation. However, if load magnitude extends far beyond tissue capacity or volume is too high, then injury may result. Many problems can be prevented if one puts a little thought into how they will manage the load-capacity relationship.