Achilles Tendinopathy: Treatment, Eccentric Exercises and Heavy Slow Resistance Training

The Achilles tendon carries some of the largest loads in the human body — during running the forces acting on it repeatedly exceed body weight. It is living tissue that adapts to stimuli: moderate, regular loading promotes remodelling and strengthening, whereas a sudden jump in load without time to adapt (new minimalist shoes, rapid mileage increase, adding intervals and hill work, returning to sport after a break) exceeds its capacity. The result is pain and gradual change in tissue structure: thickening, disorganised collagen fibre alignment and ingrowth of small blood vessels.

In the clinic this is often described as the continuum model: from reactive tendon (a short-term response to overload in which appropriate load management is enough for symptoms to recede), through a “disrepaired” tendon, to degenerative changes in which the tissue is less reversible. This is a conceptual model — not every patient passes through all stages, and ultrasound or MRI findings do not always correlate with pain (many people without symptoms have altered tendons). The practical conclusion: you treat the person and their loading, not the imaging result.

A breakthrough in conservative treatment was the work of Alfredson’s team published in 1998. The authors followed 15 recreational athletes (mean age 44 years) with chronic Achilles tendinopathy in whom earlier conservative treatment had failed. After 12 weeks of heavy-load eccentric calf training, all 15 were back to running, pain during activity had decreased, and calf strength on the affected side had caught up with the healthy side. A comparison group of 15 treated conventionally (rest, NSAIDs, shoe changes, orthoses, physiotherapy) had no success and all ended up having surgery. However, that study was small, not randomised and involved short-term follow-up — but it set off an avalanche of subsequent research.

The practical conclusion matters more than it seems. There is no single “correct” protocol: Alfredson’s eccentric scheme (slowly lowering the heel under load, performed daily in a large number of repetitions) and the HSR programme based on lifting and lowering a weight (fewer sessions per week, increasing load, slow tempo) gave comparable results. Since the results are equally good and HSR is associated with better adherence, consistency and steady load progression that the patient can actually sustain for three months matter more than the name of the method.

The general principle is the same regardless of the scheme chosen: the calf (gastrocnemius and soleus) works against resistance at a controlled tempo — slowly up and slowly down — through the whole range of motion that the tendon can tolerate. Exercises are performed with both a straight and a bent knee because they engage different parts of the calf complex. Body weight is enough at first; over time a backpack with weight or a barbell (calf-raise machine) is added, moving from more repetitions with less weight to fewer repetitions with more.

The pain rule mentioned comes from the pain-monitoring model described by the Silbernagel team: it allows moderate activity to be maintained instead of stopping sport altogether. In a randomised trial of 38 patients with Achilles tendinopathy, those who continued running and jumping under such monitoring during treatment did no worse than the active-rest group — both groups improved significantly (VISA-A-S from 57 to 85 points in the group continuing activity and from 57 to 91 in the rest group at 12 months). In other words, continuing dosed activity did no harm, but it was not better either; the conclusion that “you do not have to stop running completely” is justified, but it is not evidence that running speeds up recovery.

Tendinopathy is a problem of months, not weeks. Tendons have a relatively poor blood supply and remodel slowly, so a realistic treatment horizon is about three months to clear improvement, and a full return to demanding sport often takes longer. Patients who expect symptoms to disappear within two weeks and stop exercising make up a large share of those who later return with the same problem.

These are preliminary data — a small group, no control group — but consistent with the rest of the literature: in most patients exercise treatment is sufficient, and the proportion who have persisting or recurring symptoms is real (in this study about one fifth, plus recurrences in some people). The observation about fear of movement is practical: how a patient understands their pain affects the outcome of rehabilitation. Pain during exercise does not mean “damaging the tendon”, provided it stays within the range agreed with the therapist.

“Achilles pain” hides two different problems. Midportion tendinopathy affects the segment of the tendon a few centimetres above the heel bone; it is what the trials discussed describe, and it is the subject of the physiotherapy guideline of the Academy of Orthopaedic Physical Therapy (2024 revision, covering diagnosis, examination, imaging and physical therapy interventions). Insertional tendinopathy is located where the tendon joins the heel bone, and an additional factor plays an important role there — compression of the tendon against the bone during deep dorsiflexion of the foot.

Practical consequence: in insertional tendinopathy many protocols modify the exercises so that the heel does not drop below the level of the step, because deep dorsiflexion increases compression. This nuance is the reason it is worth being examined at least once by a physiotherapist or sports medicine doctor instead of copying a plan from the internet on your own. Pain around the insertion also sometimes comes from the retrocalcaneal bursa, the plantar fascia (a separate topic) or, less often, from inflammatory arthritis — which is why the diagnosis matters.

The Achilles tendon is particularly sensitive to the risks of steroid injections in its immediate vicinity, and many recommendations regard injections around the tendon as a method to be avoided. The review by Coombes et al. does not prove that every injection leads to rupture (serious events were rare), but it shows the main problem: short relief without lasting benefit. It is also worth remembering drugs outside orthopaedics — antibiotics from the fluoroquinolone group carry a warning in the product information about the risk of tendon inflammation and rupture; if tendon pain appears during such a course, contact your doctor.

The remaining methods — shockwave, ultrasound, laser, taping, insoles, platelet-rich plasma — have mixed or weak evidence and are treated at most as a complement to exercise, not a substitute. If a procedure brings relief, it is best used to exercise consistently; pain relief alone does not rebuild the tendon’s capacity to work.

Returning to running is not a single event but a progression. The foundation is calf strength: before we load the tendon with hundreds of repetitive stretch-shortening cycles in running, the calf should cope with demanding strength training — for example, many single-leg heel raises without increased pain and without a large difference from the healthy side. There is no single agreed standard for specific thresholds, so target values are set individually with a physiotherapist.

From the point of view of an active person whose Achilles pain has started to limit running, the most valuable conclusion from the literature is that you do not need to search for a miracle method. The well-documented things are simple: regular calf strength training with increasing weight, control of load in sport and patience on the scale of three months. The choice between eccentric exercises and HSR is a matter of preference and logistics — what matters is that the plan is realistic enough to be sustained, because in the trials it was attendance that distinguished the best-tolerated programmes.

If there is no improvement after three months of consistent training, this does not mean that exercises “do not work” — more often it means that the diagnosis needs checking or the programme needs adjusting (weight, tempo, load management in sport). Then it is worth consulting a sports medicine specialist or physiotherapist rather than changing method every two weeks. The wider importance of strength training for joints and tendons is described in our knowledge-base entry on strength training.