There are three types of muscle contractions, so it can be confusing to know which kind to choose to get stronger. Your 3 options are: eccentric, where the muscle lengthens as it contracts, like the quadriceps muscles do as you go down the stairs, concentric, where the muscle shortens such as during a seated knee extension, and isometric, where the muscle fibers stay the same length during the contraction, like the quadricep muscles do during a wall sit.
Eccentric exercise is commonly prescribed by physiotherapists, especially when treating clients with tendon injuries. This type of strengthening has been shown to be more effective than concentric strengthening at minimizing muscle atrophy and improving muscle force production. While there has been some evidence to show that isometric exercises can be helpful in reducing pain, eccentric exercise in isolation or as an adjunct has been shown in the literature to be the most effective for reducing pain and improving function (Chen & Baker 2021). Eccentric and isometric movements are more common during your everyday movements – this is why it is important to train these movements after an injury.
The most important part of this rehabilitation process is to keep moving, but to avoid painful activities. We need to avoid complete unloading (or resting) of the tissues, as this can promote weakness and degeneration of the tendon. Your physiotherapist will work with you to figure out which exercises are best suited for your injury and get you back to what moves you.