Achilles Tendon Pain from Running: Causes & Treatment

The Achilles tendon is the strongest tendon in the human body — during running it handles forces of six to twelve times your body weight. Exactly this enormous workload makes it vulnerable when training rises faster than the tissue can adapt. Achilles tendon pain, medically called tendinopathy, is among the most common running injuries of all: studies show that roughly one in ten recreational runners is affected in any given year — among marathon runners, lifetime prevalence exceeds 50 percent. The good news: with the right load management and targeted tendon training, the vast majority of cases heal without surgery.

Two types: mid-portion or heel attachment

Not every case of tendinopathy is the same — and the distinction determines the right treatment. In mid-portion tendinopathy the pain sits two to six centimeters above the heel bone, in the middle of the tendon. It accounts for about two thirds of all cases. Typical is a noticeable thickening of the tendon that feels like a spindle-shaped knot.

Insertional tendinopathy, by contrast, sits directly at the attachment on the heel bone. Caution is needed here: exercises off a step edge, where the heel drops below forefoot level, press the tendon against the bone and can worsen the irritation. Aggressive stretching is counterproductive at the insertion too — more on that later.

Both types share the classic symptoms: morning stiffness in the calf, usually lasting less than 30 minutes, a start-up pain that initially eases after a few hundred meters of running, and tenderness when the tendon is pinched between two fingers. The fact that pain fades during the run is deceptive — it often returns amplified in the evening or the next morning.

The real cause: load spikes, not "wear and tear"

Achilles tendinopathy is almost never a wear-and-tear problem but a load management problem. Tendon tissue adapts to training — but significantly more slowly than the cardiovascular system and muscles. After four weeks of interval training, your fitness already allows tempo runs that your tendon can only structurally handle after eight to twelve weeks. The injury falls into this gap.

The typical triggers in practice:

• Volume spikes: weekly increases above ten percent, training camps, spontaneous long runs.
• New intensities: the first interval session of the season, sprint work, hill running — all loads with high tendon forces.
• Shoe changes: from cushioned shoes with a high drop to flat or barefoot-style models. The lower heel height lengthens the lever and raises tendon strain by up to 15 percent.
• Returning after a break: resuming your old volume after injury, a cold or vacation as if nothing had happened.

On top come risk factors you cannot change: the main age of onset is between 30 and 50, men are affected more often than women, and limited ankle mobility raises the risk. Important to know: certain antibiotics from the fluoroquinolone group (such as ciprofloxacin) demonstrably weaken tendon tissue — intense training should be paused while taking them.

Runners who manage their training load systematically can avoid exactly these spikes. The ratio of acute to chronic workload (ACWR) shows when the weekly load exceeds the tolerable range — details in the article on ACWR and training load.

Pain monitoring: train, don't rest

The most important insight of modern tendon research: complete rest does not cure tendinopathy. Tendons need mechanical load to remodel and strengthen — athletes who do nothing for weeks return with an even weaker tendon and often experience the same complaints on their comeback.

Instead, clinicians work with the pain-monitoring model (after Silbernagel), which is standard in sports physiotherapy:

• During loading, pain up to 5 out of 10 on the pain scale is acceptable — but it should not force you to limp or change your technique.
• The next morning, stiffness must be back at baseline. This is the decisive test: if the tendon reacts more strongly overnight, the load was too high.
• Across the week, pain must not creep upward. If it does, drop back a gear.

In practice this means: easy runs on flat terrain are usually still possible — with reduced volume and without sprints, strides and hill work, because exactly these produce the highest tendon forces. Your early indicator is morning stiffness: roughly measure each day how many minutes your calf needs after getting up to feel normal. If the value stays stable or falls, the load fits. If it rises over several days, reduce. This logic of load adjustment is also the core principle of injury prevention in running in general.

Eccentric training: the Alfredson protocol

The most effective conservative treatment is not a drug but training. The Alfredson protocol from 1998 is still the gold standard for mid-portion tendinopathy — in the original studies, around 90 percent of athletes returned to training pain-free with it:

• Exercise: heel raises on a step edge. Push up on both feet, then lift the healthy leg and lower the injured leg slowly over 3–5 seconds — only the lowering phase ("eccentric") loads the affected leg.
• Dosage: 3 sets of 15 repetitions, twice daily, for twelve weeks. Once with a straight knee (gastrocnemius), once with a slightly bent knee (the deeper soleus muscle).
• Progression: once it becomes pain-free, add weight in a backpack or on a dip belt — the tendon needs progressive overload, otherwise there is no adaptation stimulus.
• Pain during the exercise is expected up to about 5 out of 10 — that is part of the principle, not a warning sign.

For insertional tendinopathy an important modification applies: exercise on flat ground only, the heel does not drop below floor level. This avoids the harmful compression at the bone attachment.

An equally effective alternative is heavy slow resistance (HSR): heavy, slow exercises such as calf raises on the leg press or at a Smith rack, three times per week with substantial weight. Comparative studies show similar outcomes to Alfredson — and if you already do strength training as a runner, you can integrate HSR directly into your existing program.

What else helps — and what doesn't

• Stretching: counterproductive at the insertion (compression), effect-neutral for the mid-portion. Invest your time in strength training rather than stretching routines.
• Heel lifts or insoles: a small heel lift (6–12 mm) measurably unloads the tendon short-term and can ease the first week. It heals nothing — it is a bridge, not a therapy.
• Shoes with a drop: models with an 8–12 mm drop make sense for the rehab phase. Switch to flat shoes only after complete freedom from symptoms, and then transition over weeks.
• Cortisone injections into the tendon: not an option. They relieve short-term but weaken the collagen scaffold and markedly raise the rupture risk.
• Shockwave therapy: for chronic courses beyond six months, an evidence-based addition — but always combined with tendon training, never instead of it.
• Plyometrics and jump training: only in the late stage, once weighted calf raises are pain-free. Then rebuild in doses — see the article on plyometrics for runners.

Common mistakes with Achilles tendon problems

• Training through it for months. Ignoring early symptoms for three months lands you in the chronic phase — and that takes far longer. The first two to three weeks are the window in which adjustment still works quickly.
• Only resting, not building. Rest without tendon training leads to the vicious circle: better, break, return, same pain.
• Returning to speed and hills too early. Sprint-type and uphill loads belong at the end of rehab, not the start. Rule of thumb: only when daily life and easy running have been symptom-free for two weeks.
• Not fixing the cause. If the load spike stays in your plan, the tendinopathy returns. Without controlling weekly load you are only treating symptoms.

When you need to see a doctor

Most cases of tendinopathy can be managed on your own — but three situations belong in professional hands: first, the sudden, whip-like pain with a kicked-in-the-calf feeling: suspected rupture, an emergency. Second, marked swelling, redness and warmth, especially with fever: inflammation of the tendon sheath or bursa must be ruled out. Third, no improvement after twelve weeks of consistently performed eccentric training — then imaging and extended options like shockwave therapy make sense.

How Peakora helps prevent Achilles problems

The decisive prevention is load management — and that is exactly what the Peakora engine does automatically: it limits volume increases, tracks your acute and chronic workload, and warns when weekly load leaves the tolerable corridor. The morning check-in with sleep and wellbeing detects deterioration before it becomes an injury, and the adaptive plan drops back a gear on overload signals instead of stubbornly pushing on. That way you train hard enough for progress — and dosed enough for healthy tendons.

Frequently asked questions about the Achilles tendon and running