Written and reviewed by the BPR clinical team. Last reviewed: 30 July 2026. This article is for education and is not a substitute for individual assessment, diagnosis or treatment by a qualified healthcare professional.
It often starts as a morning stiffness in the back of the heel that eases once you get going, then a soreness that builds after runs. The Achilles — the thick cord connecting your calf to your heel — is the strongest tendon in the body, but it's also a common site of overload pain, especially in runners. Like other tendon problems, it can be stubborn, and like other tendon problems, the answer is loading rather than rest.
What is Achilles tendinopathy?
Achilles tendinopathy is an overload condition of the Achilles tendon. It can affect the middle of the tendon (the more common “mid-portion” type) or where it attaches to the heel bone (the “insertional” type), and the two are managed slightly differently. Despite the old “tendonitis” label, it isn't mainly inflammation — it's a tendon struggling to keep up with the demands placed on it, which is why it needs graded loading to recover (Martin et al., 2024).
Why does it happen?
The classic trigger is a change in load — more running, faster running, more hills, a new surface or new footwear — that outpaces what the tendon is prepared for. Calf weakness, and simply getting a little older, add to the risk. As with tendons elsewhere, it's usually a case of too much, too soon.
What does it feel like?
The hallmark is pain and stiffness in the tendon that's worst first thing in the morning and after periods of rest, then eases as you warm up, only to feel worse again a few hours after activity. You may notice a tender, sometimes thickened spot in the tendon. Mid-portion pain sits a few centimetres above the heel; insertional pain sits right at the heel bone.
How it's assessed
We'll press along the tendon to locate the painful area, load it with calf-raise-type tests to reproduce your symptoms, and assess your calf strength. Working out whether it's the mid-portion or insertional type matters, because it changes how we set up your loading. We'll also make sure it isn't something that needs a different plan — in particular, ruling out a tendon rupture.
What the evidence says
- Loading works. Heavy calf-loading exercise has decades of evidence behind it; Alfredson's eccentric-loading programme was the landmark study showing marked improvement in chronic Achilles tendinopathy (Alfredson et al., 1998).
- Guidelines make loading the mainstay. The current clinical practice guideline recommends progressive calf and tendon loading — including eccentric and heavy-slow resistance exercise — as the first-line treatment (Martin et al., 2024).
- Passive treatments are add-ons. Guidance positions hands-on techniques and other modalities as adjuncts that support loading, not replacements for it (Martin et al., 2024).
How it's treated
Progressive loading is the cornerstone. The classic approach uses heavy calf-strengthening exercises, and current guidance supports progressive calf and tendon loading — including heavy-slow resistance — as the mainstay of treatment (Alfredson et al., 1998; Martin et al., 2024). Managing your running load while you build the tendon's capacity is part of the same plan.
Hands-on treatment and other adjuncts can help you stay comfortable, but they don't replace the loading. Insertional Achilles pain needs a gentler starting point, because positions that compress the tendon against the heel bone can aggravate it — another reason the type matters.
What you can do yourself
Keep up your prescribed calf-loading exercises — they're the engine of recovery — and manage your running load rather than stopping completely, unless advised otherwise. Use the 24-hour rule: some discomfort with exercise is acceptable as long as it settles by the next morning. Check your footwear and build any increases in training gradually.
When to seek help
When to seek help. Seek urgent attention if you feel a sudden, sharp pain or a “pop” at the back of the ankle and then struggle to push off or walk normally — this can signal an Achilles rupture rather than a tendinopathy. Otherwise, see someone if the pain has settled into a pattern, is limiting your running, or isn't improving with your own loading.
Frequently asked questions
Should I stop running?
Usually not completely. Most people can keep running in a modified way while loading the tendon, guided by the 24-hour rule — pain that settles by the next morning is generally acceptable.
Eccentric or heavy-slow resistance — which is better?
Both are effective and supported by guidelines. The best programme is often the one you'll do consistently; a clinician can tailor it to your tendon and goals.
How long does it take to get better?
Achilles tendinopathy commonly takes a few months to settle properly. Consistency with loading and sensible running load are what shorten the road.
Why is it worse first thing in the morning?
Morning stiffness that eases as you warm up is a classic feature of tendinopathy, and it's a useful marker to track as you improve.
When could it be a rupture rather than tendinopathy?
A sudden sharp pain or 'pop' at the back of the ankle, often with difficulty pushing off or walking, needs urgent assessment to rule out a rupture.
How BPR can help
At BPR we'll identify which type of Achilles problem you have, rule out the serious causes, and build you a staged loading programme that gets you back to running without the morning stiffness. You can book an assessment at bpr.rehab.
References
- Alfredson, H., Pietilä, T., Jonsson, P. and Lorentzon, R. (1998) 'Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis', American Journal of Sports Medicine, 26(3), pp. 360–366. doi:10.1177/03635465980260030301.
- Martin, R.L., Chimenti, R., Cuddeford, T. et al. (2024) 'Achilles pain, stiffness, and muscle power deficits: midportion Achilles tendinopathy revision 2024. Clinical practice guidelines', Journal of Orthopaedic & Sports Physical Therapy, 54(12), pp. CPG1–CPG38. doi:10.2519/jospt.2024.0302.