Tendon injury from too much use is a very common problem in sport. It occurs when the cumulative strain on the tendon is greater than what the tendon can take. There is two parts to this: the first is the cumulative load and that means just how much exercise is carried out and how frequently this is done. It is essential that the tendon is given time to adapt to those loads or the cumulative load will exceed that. That's the second aspect, just how adapted the tendon would be to those loads. Understanding these concepts is important in being familiar with and managing tendonitis.
One example is, peroneal tendonitis that is an overuse injury occurring on the outside of the ankle joint. The collective load in this tendon is higher when exercise levels are too high or increased too quickly and not sufficient time is provided for the tendon to adapt to those higher loads. The cumulative load is also increased by the biomechanics of the foot. As an example, if the supination resistance of the foot is reduced then the peroneal muscles on the outside of the lower limb will be required to work harder. That could put an increased strain on the peroneal tendons and then put together with training errors that load might possibly exceed what the tendon can take and it develops tendonitis.
Based on these concepts, peroneal tendonitis is managed by reduction of that cumulative load. That will mean exercising amounts and frequency should be reduced somewhat to allow the tendon to adapt to the loads. The load in this disorder can also be reduced with foot orthotics that evert the foot, which means the peroneal muscles does not need to work so hard. Then the tendon must be given a chance to get used to the loads. This means that exercising volume and frequency needs to be slowing increased, with plenty of rest between training loads to get the tendon to adjust to those stresses.