Achilles Tendinopathy.
Achilles tendinopathy (often called Achilles tendinitis) is a degenerative condition of the Achilles tendon — the thick band connecting the calf muscles to the heel bone. It presents as pain and stiffness in the tendon, typically 2-6 cm above the heel, and is most common in runners who have recently increased their volume, intensity or hill work.
Overview
The Achilles tendon is the strongest and thickest tendon in the human body, bearing loads of 6-8 times body weight during the push-off phase of running. Tendinopathy develops when the rate of tendon collagen breakdown exceeds the rate of repair and remodelling, leading to collagen disorganisation, neovascularisation (abnormal blood vessel growth) and pain. There are two distinct types: mid-portion tendinopathy (2-6 cm above the heel insertion, most common in runners, accounting for 75% of cases) and insertional tendinopathy (at the calcaneal attachment, often associated with bone spurs). The distinction matters because treatment approaches differ.
Causes and biomechanics
The most common trigger is a sudden increase in training volume beyond 10% per week, which overloads the tendon before it has time to adapt. Excessive hill running or speed work increases the eccentric loading on the Achilles during push-off. Transitioning abruptly from higher-drop shoes (10-12mm) to lower-drop or minimalist shoes (0-6mm) shifts load onto the Achilles. Tight calf muscles (both gastrocnemius and soleus), insufficient recovery between hard sessions, and running in cold weather without adequate warm-up are contributing factors. The tendon adapts to training load 3-5 times more slowly than muscle tissue, so runners frequently outpace their tendon's structural capacity during rapid fitness gains.
Symptoms
Pain and stiffness in the Achilles tendon region, typically worst first thing in the morning (morning stiffness lasting more than 30 minutes suggests active tendinopathy) and after prolonged sitting. Pain may decrease during the warm-up phase of a run as tendon compliance increases, but returns after cooling down — a classic pattern called the 'warm-up phenomenon.' In advanced cases, the tendon may feel thickened, nodular or tender to palpation. Crepitus (a creaking or crackling sensation) may be present during active ankle dorsiflexion and plantarflexion.
Eccentric loading protocol
The Alfredson protocol is the gold standard evidence-based treatment for mid-portion Achilles tendinopathy. Eccentric heel drops stimulate tendon remodelling by applying controlled mechanical load to the degenerative tissue. Technique: stand on a step, raise onto both feet (concentric phase), then shift weight to the affected side and lower the heel slowly below step level over 5 seconds (eccentric phase). Perform 3 sets of 15 repetitions, twice daily (total 90 reps per day), for a minimum of 12 weeks. Pain during the exercise is expected and acceptable up to 5/10 — this is a deliberate loading protocol, not a pain-free exercise.
Prevention
Maintain calf strength with regular eccentric heel raises (3x15, 3 times per week) even when completely asymptomatic — this builds tendon resilience proactively. Increase training volume gradually following the 10% rule. Avoid abrupt changes in shoe drop height (transition over 4-6 weeks). Warm up with dynamic calf raises and ankle circles before speed work or hill sessions. Male runners over 40 are at highest risk due to age-related tendon degeneration and should be particularly attentive to Achilles health, including monitoring morning stiffness as an early warning sign.
Return to running
Continue running at reduced volume (50-70% of normal) if morning stiffness resolves within 30 minutes of waking and pain stays below 4/10 during and after running. Avoid hills and speed work for a minimum of 6-8 weeks — flat, easy running only. Full return to unrestricted training typically takes 3-6 months of consistent eccentric loading. Never stretch the Achilles aggressively (passive dorsiflexion stretches can compress the tendon at its insertion) — the Alfredson eccentric protocol provides the mechanical stimulus the tendon needs for remodelling. Maintain the eccentric loading protocol as a permanent part of your strength routine to prevent recurrence.
Frequently asked questions
What does Achilles tendinopathy feel like?
Achilles tendinopathy presents as pain and stiffness in the tendon 2-6 cm above the heel (mid-portion) or at the calcaneal insertion. Morning stiffness lasting more than 30 minutes after rising is the classic early sign. Pain often decreases through the warm-up phase of a run — the 'warm-up phenomenon' — but returns after cooling down. In chronic cases the tendon may feel thickened or nodular to palpation.
Should I rest or run through Achilles pain?
Full rest is usually the wrong answer — tendons require progressive mechanical load to remodel, and complete rest often results in a weaker, more fragile tendon when you return. You can typically keep running at 50-70% of normal volume if morning stiffness clears within 30 minutes of waking and pain stays below 4/10. Pair every run with the Alfredson eccentric protocol. Stop completely only if morning stiffness is worsening week-over-week or pain forces you to limp.
How long does Achilles tendinopathy take to recover?
The Alfredson protocol is a minimum 12-week commitment. Most runners see meaningful improvement at 6-8 weeks and full resolution at 3-6 months. Insertional tendinopathy (pain at the heel bone attachment) typically takes longer than mid-portion tendinopathy. Tendons adapt 3-5 times more slowly than muscle, so recovery feels frustratingly gradual even when training is calibrated correctly.
Why is eccentric loading the gold standard for Achilles?
Eccentric heel drops apply controlled, progressive mechanical load to the degenerative tendon tissue, stimulating collagen remodelling and restoring fibre alignment. Randomised trials show the Alfredson protocol outperforms stretching, shockwave therapy, corticosteroid injection and PRP for mid-portion tendinopathy. Pain during the exercise (up to 5/10) is acceptable and is part of the loading stimulus — this is not a pain-free exercise.
Is insertional Achilles tendinopathy different from mid-portion?
Yes. Insertional tendinopathy (pain at the heel bone attachment, often with a bone spur) does not tolerate the full below-step-level eccentric drop of the Alfredson protocol because that position compresses the tendon at its insertion. Modify by performing heel drops on a flat floor rather than below step level, and consider a temporary 5-10 mm heel lift to reduce insertional compression. Stretching the Achilles is particularly counter-productive for insertional cases.
What shoes help with Achilles pain?
During recovery, a slightly higher heel-to-toe drop (8-12mm) reduces tendon loading by shortening the working range. Avoid zero-drop and minimalist shoes until symptoms fully resolve. A temporary 5-10 mm heel lift or orthotic wedge can be inserted into your regular shoes to further unload the tendon in the acute phase. Once recovered, transition back to your normal shoe geometry gradually over 4-6 weeks, never abruptly.
Can I do calf stretching with Achilles tendinopathy?
Aggressive passive stretching is contraindicated, particularly for insertional tendinopathy — pulling the foot into deep dorsiflexion compresses the tendon at its attachment and can worsen the condition. The Alfredson eccentric protocol itself provides sufficient tendon range and mechanical stimulus; additional static stretching is unnecessary and potentially harmful. If calves feel tight, foam-roll the gastrocnemius and soleus muscle bellies rather than stretching the tendon.
This article is for educational purposes only and does not constitute medical advice. If you are experiencing pain or injury, consult a qualified sports medicine physician or physiotherapist before modifying your training. Read our full medical disclaimer.