Chronic tendinopathy, an umbrella diagnosis that includes tendinosis (degeneration of the intratendonous tissue), paratendinosis (degeneration of the tissue around the tendon) and tendinosis with paratendinosis, is a very common condition amongst the running set. Research suggests that 52% of runners will experience this condition over the course of their lifetime and in a given year, 9% of runners can expect to deal with it.
Tendinopathy is a degeneration of the tendon that is not predominantly marked by inflammation and is longer term (more than 3 months) in duration. This differentiates from tendonitis which is an acute condition (less than 3 months and more like less than a week in my opinion) marked by inflammation - swelling, redness and heat. Many treatment interventions exist for tendinopathy ranging from exercise and biomechanical training, to steroid injections, to nitrous oxide patches, to dry needling (IMS), to extracorporeal shockwave therapy and beyond. The intervention that by far has the most research support for its efficacy is exercise and biomechanical training, although to be fair dry needling also has a good body of research supporting its use. Most other interventions lack sufficient research evidence to support or refute their use in clinic.
So what type of exercise (and biomechanical training) should be used? And who even says the words "biomechanical training" with a straight face, let alone implements it in a clinical training context? Strength training for this condition should be heavy-load, eccentric and controlled. For example heel drops over a step or reverse lunges, both with enough weight (if more than bodyweight is required) appropriate for sets of 7 repetitions. Incidentally other tendinopathy research has suggested protocols that include stretching before and after the eccentric strength training exercise, so it's reasonable to suggest 3 repetitions of an achilles stretch before and after in this case as well. Check out the video for some quick and dirty stretch suggestions.
The "biomechanical training" is the part of the exercise that demands control, a concept for which I have a no-so-secret professional love affair. Beautiful movement is the goal for all of us as athletes - and we should all think of ourselves as athletes! Beautiful movement is the transition with strength and grace from one stable position to another stable position. When executed, it looks pretty, it feels pretty and as an added bonus it is protective against injury. For achilles exercises this requires first keeping the foot in good position (avoiding overpronation), keeping the knee aligned in the transverse plane with the foot and generally organising the trunk so that mastoid is over shoulder is over hips - I explain in more detail in the video.
Remember too that patience is a virtue, research suggests that it takes about 12 weeks of daily exercise training to deal with a tendinopathy. Load progressions must be done carefully and should not be so abrupt as to irritate the condition (which I personally define as an increase in pain level that lasts longer than an hour after exercise). Keep your movement patterns pretty! As always, if in doubt ask your friendly physiotherapist for guidance!
Further reading (if you really want to dig deep).
Scott, A., Huisman, E., & Khan, K. (2011). Conservative treatment of chronic Achilles tendinopathy. Canadian Medical Association Journal, 183(10), 1159-1165.