Tendon injury from excessive or overuse is a very common problem in sport. It occurs when the cumulative load on the tendon is greater than what the tendon is designed to take. There is two parts to this: the first is the collective repetitive load and that means just how much activity is taken on and how frequently this is done. It is vital that the tendon has time to get used to those loads or the cumulative load could exceed that. Which is the second part, just how adapted the tendon would be to those loads. Understanding these concepts is very important in being familiar with and managing tendonitis.
For example, peroneal tendonitis which is an overuse injury that occurs on the outside of the ankle joint. The cumulative load in this tendon is increased when activity amounts are too high or increased too quickly and not sufficient time is given for the tendon to adapt to those higher loads. The cumulative load is also increased by the biomechanics of the feet. For example, if the supination resistance of the foot is reduced then the peroneal muscles on the outside of the leg will be required to work harder. That can put an increased stress on the peroneal tendons after which along with training errors that load could very well go beyond what the tendon can take and it develops tendonitis.
Based upon these principles, peroneal tendonitis is managed by reducing that collective load. That can mean exercising volumes and frequency need to be reduced somewhat to permit the tendon to adapt to the loads. The load in this disorder will also be decreased with foot orthotics that evert the foot, which means the peroneal muscles does not need to work so hard. Then the tendon really should be given a chance to adapt to the loads. This means that training volume and frequency has to be slowing increased, with lots of rest between training loads to give the tendon to adjust to those loads.