Tendon pain: A symptom of failed loading

Tendon pain: A symptom of failed loading teaser image
Overuse tendinopathies can be severely debilitating for a wide range of the population. They are common injuries that can severely limit general exercise capacity, athletic and work performance. Exercise is a well-known component for most tendinopathy rehabilitation programs, but errors in exercise or activity prescription can also lead to ongoing pain and disability.

For successful management of chronic tendinopathy, practitioners and patients must understand that in nearly all cases tendon pain is a symptom of failed loading. In other words, the tendon has been loaded more than what it can tolerate. The load tolerance of a tendon is always individual, but the concept of load response is universal. Cook and Purdam describe the mechanism of tendon load response excellently in the visual below:

They suggest tendinopathy is directly associated with excessive load (plus individual factors) of the tendon, leading to reactive tendinopathy. Without effective management, this can lead to tendon dysrepair (reduced ability to regenerate and repair) and ultimately chronic, degenerative tendinopathy. The changes between a normal tendon and degenerative tendinopathy should be viewed as a continuum.

“Excessive load” however, is not only unique to the individual, but unique at any point in time. Tendons, like all tissues, respond and adapt to stimulus or lack thereof. An unloaded tendon becomes stress-shielded and loses collagen integrity and alignment. This in itself is unlikely to produce pain, but once the tendon is reloaded - even if the load would have previously been “optimal” or “normal” for that individual -  it no longer has capacity to tolerate.

Consider a mostly sedentary, middle-aged man, who starts training hard for a 12km fun run, despite many months of no exercise. His Achilles tendons are less likely to have the adaptation to tolerate a sudden increase in load, compared to a regular runner completing the same training. On the other end of a spectrum, a gymnast, despite having what most would consider to be strong, load tolerant Achilles, may still be susceptible to reactive tendinopathy simply due to the sheer forces required for flips and somersaults. A subtle change in training regime may the difference between normal, healthy tendons and reactive tendinopathy.
Management of tendon pain via exercise is as individual as the cause of the tendinopathy. Isometric strength training, eccentric loading exercise, and heavy slow resistance exercise have all been shown to be beneficial for tendon pain. However the application of these types of tendon loading regimes should be individually considered based on the current load tolerance of the tendon, and the load requirements of the tendon at full function. Do you need your Achilles to handle a marathon run or a triple jump?