Running builds a stronger heart, lungs, and bones — but it loads the tendons hard, and the Achilles is especially vulnerable. Achilles tendonitis in runners is common, stubborn, and, contrary to popular belief, does not respond to complete rest. The most effective treatment is a progressive calf-strengthening programme. This guide sets out exactly how to rehab it and return to running.

For the full list of conditions that mimic it, see Achilles tendon pain after running; for the clinical overview, see Achilles tendinopathy.

What is the Achilles tendon?

Named after the Greek hero, the Achilles is the largest, strongest tendon in the body. It joins the gastrocnemius and soleus calf muscles to the heel bone, transmitting force from foot to body — the spring that lets us sprint and change direction.

What happens in Achilles tendonitis?

Loaded gradually, the tendon adapts by thickening and stiffening. Loaded too fast, the collagen breaks down faster than it heals; the tendon swells, transmits force poorly, and becomes painful.

Typical findings in runners

Runners report Achilles pain that is worse in the morning, warms up with activity, and flares afterwards — anything with a spring motion (running, jumping) aggravates it. We always look for the cause: a sudden rise in training load, calf weakness, or reduced ankle movement. Conditions such as obesity, diabetes, and high cholesterol also raise the risk, probably through inflammation.

Imaging (ultrasound or MRI) confirms the tendon thickening and collagen breakdown and rules out paratenonitis or a tear. Ultrasound is cheaper and easy to use at the first review.

The most effective treatment: calf strengthening

Collagen breakdown does not respond to rest — quite the opposite. Runners improve with a progressive calf-strengthening programme.

First, reduce the harmful load. Cut running or stop jumping if pain is distressing. As a rule, drop step count or running by about 50%; stop entirely only if pain is severe.

Can you run through it? Yes, if the pain is stable — low-level (under 2–3/10), settling within a day. Unstable pain (over 3/10, lasting beyond 24 hours, needing ibuprofen) means you’re doing too much.

The exercise progression

Strengthen both calf muscles — gastrocnemius and soleus — which works better than either alone:

  • Build strength: bent-knee and straight-knee calf raises, 2–3 times per week, single-leg where possible. Once you manage eight reps, add weight.
  • Strength goals before progressing: about 0.5× body weight on a standing calf raise; 1–1.5× body weight on a seated calf raise.
  • Add plyometrics: skipping and hopping, progressing double- to single-leg, up to the stiff-knee “pogo” hop. Stiff-ankle stair climbs to a metronome at 90–100 bpm work well.
  • Then return to running: once you tolerate plyometrics, you’re ready to rebuild running.

Also strengthen the quadriceps, hamstrings, and pelvic muscles. An experienced strength and conditioning coach improves results.

Treatments that support the exercises

When rehab needs help, we add shockwave therapy (best combined with calf strengthening), GTN patches, and collagen supplements. In difficult cases, an injection may reduce pain and unlock rehab — but we avoid cortisone in the Achilles, since it weakens the tendon and risks rupture. Dr Masci will discuss the pros and cons of each injection option.

Frequently asked questions

Should I stop running completely with Achilles tendonitis?

Usually not. Reduce load rather than stopping, and keep pain stable (under about 3/10, settling within a day). Complete rest deconditions the tendon and slows recovery — strengthening is what heals it.

How long does Achilles tendonitis take to settle in runners?

Often 3–6 months of consistent strengthening, sometimes longer. Persistence is the strongest predictor of recovery.

Why does my Achilles feel worse in the morning?

Morning stiffness is characteristic — the tendon stiffens overnight after loading. It typically eases after a few minutes of gentle movement.

Do I need both seated and standing calf raises?

Yes. Standing raises target the gastrocnemius, seated (bent-knee) raises target the soleus. Training both is more effective than either alone.

Final word from Sport Doctor London about Achilles tendonitis in runners

Achilles tendonitis is common in runners, and the most effective treatment is calf strengthening — not rest. Supervised exercise works best, supported by shockwave, GTN patches, or injections in difficult cases.

Dr Lorenzo Masci is a Sports and Exercise Medicine consultant specialising in tendons. To book a one-stop Achilles assessment in London, contact his team here or call +44 (0) 203 488 0350.

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