Tendon injury from overuse is a common issue in sport. It happens when the cumulative strain on the tendon exceeds what the tendon can take. There is two parts to this: the first one is the collective load and that means just how much exercise is undertaken and how often it is done. It is vital that the tendon has time to adapt to those loads or the collective load could go beyond that. That's the second aspect, just how adapted the tendon is to those loads. Being familiar with these concepts is very important in being familiar with and dealing with tendonitis.
One example is, peroneal tendonitis which is an excessive use injury occurring on the outside of the ankle joint. The cumulative load in this tendon is higher when physical activity 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. For instance, if the supination resistance of the foot is low then the peroneal muscles on the outside of the leg will likely need to work harder. That could put an increased strain on the peroneal tendons and then combined with training errors that load could very well go beyond what the tendon can take and it develops tendonitis.
Based upon these concepts, peroneal tendonitis is treated by reduction of that cumulative load. That will mean training amounts and frequency has to be reduced somewhat to allow the tendon to adapt to the loads. The stress in this disorder can also be reduced with foot orthotics that evert the foot, which means the peroneal muscles will not need to work so hard. Next the tendon ought to be given a chance to adapt to the loads. This implies that training amount and frequency needs to be slowing increased, with lots of rest between training loads to get the tendon to adapt to those loads.