Tendon injury from excessive use is a common injury in sport. It happens when the cumulative load on the tendon is greater than what the tendon can take. There is two parts to this: the first is the collective load and that means just how much exercise is done and just how frequently it is done. It is necessary that the tendon has time to get used to those loads or the collective load can go beyond that. That is the second part, just how adapted the tendon is to those loads. Being familiar with these principles is crucial in understanding and managing tendonitis.
As an example, peroneal tendonitis which is an overuse injury occurring on the outside of the ankle joint. The cumulative load in this tendon is increased when activity levels are too high or increased too quickly and not enough time is provided for the tendon to adapt to those high loads. The cumulative load can also be increased by the biomechanics of the feet. For instance, if the supination resistance of the foot is reduced then the peroneal muscles on the outside of the lower limb will need to work harder. That could put an greater force on the peroneal tendons after which in addition to training errors that load can exceed what the tendon can take and it develops tendonitis.
Based on these principles, peroneal tendonitis is managed by reduction of that collective load. That will mean exercising amounts and frequency have to be decreased somewhat to allow the tendon to adapt to the loads. The load in this condition will also be decreased with foot orthoses that evert the foot, which means the peroneal muscles does not need to work as hard. Next the tendon has to be given a chance to get used to the loads. This implies that training amount and frequency needs to be slowing increased, with plenty of rest between training loads to get the tendon to adjust to those loads.