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.
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.
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