Guide

Achilles tendinopathy in runners: why slow, heavy loading beats rest

Achilles pain is the injury runners try to rest away. Two weeks off, some calf stretching, a shoe with a bigger heel — and the first steps out of bed still feel like walking on a rope that's been left out overnight. Then the mileage comes back, and so does the tendon. The stubborn cases usually aren't an inflammation you wait out. They're a tendon that has lost the capacity to handle what running asks of it, and in the trials below that capacity came back the same way each time: slowly, under weight.

The pattern that identifies it

The classic signature is stiffness and pain in the tendon above the heel on the first steps of the morning, easing as you move, then returning after a run or after you've sat for a while. Press along the tendon a few centimetres above the heel bone and there's often a tender, slightly thickened spot. That pattern is what's usually called mid-portion Achilles tendinopathy, and it's the version most of the loading research below is about.

Pain right at the heel bone, where the tendon attaches, is the insertional version, and it behaves differently: lowering the heel below a step presses the tendon against the bone, so the protocol below usually gets modified — raises from the floor, no heel drop. If your pain is at the bone rather than above it, have the plan tailored by someone who can look at it.

The change of word matters here too. What tissue samples show in long-standing cases is mostly degenerative change — collagen that has been overloaded and hasn't rebuilt in order, with some inflammatory activity mixed in — rather than the acute inflammation of a fresh injury, which is why the literature moved from "tendinitis" to "tendinopathy". Rest on its own asks nothing of that tissue, and the one trial that tested simply waiting it out (below) found waiting came last.

The 1998 study that flipped the default

In 1998 a Swedish group took 15 recreational athletes, average age 44, whose Achilles pain had lasted long enough and resisted enough conventional treatment that none of them could run. For twelve weeks they did heavy eccentric heel drops: rise up on both feet on a step, lower slowly on the sore leg alone, three sets of fifteen, twice a day, once with the knee straight and again with it bent, adding weight in a backpack once a load stopped hurting. At twelve weeks all fifteen were back to running at their pre-injury level, pain during activity had dropped sharply, and calf strength on the sore side had caught up with the other leg. (Alfredson et al., 1998)

The comparison group is the part worth sitting with. Fifteen athletes with the same diagnosis had been treated the conventional way — rest, anti-inflammatories, shoe changes and orthotics, physiotherapy — and none of it had worked. Every one of them ended up in surgery.

Be honest about what that is: a small study, not randomised, short follow-up, done on people who had already failed everything else. On its own it doesn't settle anything. What it did was flip the default. Before it, the advice was rest. After it, the advice was load, and the trials since have been about which load, not whether.

Waiting it out was tested too

The missing piece in 1998 was a fair comparison with doing nothing. A 2007 randomised trial supplied it: 75 people whose mid-body Achilles tendinopathy had lasted more than six months and already failed injections, anti-inflammatories and physiotherapy were split three ways — heavy eccentric loading, shock-wave therapy, or wait and see. Four months on, 60% of the loading group rated themselves recovered or much improved, against 24% of the wait-and-see group; on the standard Achilles function score the loading group went from 51 to 76 and the waiting group from 48 to 55. The authors' conclusion was blunt: waiting was ineffective. (Rompe et al., 2007)

Heavy and slow does the same job in less time

The eccentric protocol has a compliance problem: 180 heel drops a day, every day, for three months. A 2015 randomised trial in Denmark asked whether ordinary heavy, slow strength training — lifting and lowering, three sessions a week — could match it. Fifty-eight people with chronic mid-portion tendinopathy were split between the two. The heavy-slow group did calf raises with a three-second lift and a three-second lower, starting at a weight they could manage fifteen times and working over twelve weeks to a weight they could manage six times.

At twelve weeks both groups had improved by about the same amount on function and pain, and at a year the gains had held in both. The difference that did reach significance was attendance: the eccentric group completed 78% of their sessions, the heavy-slow group 92%. Satisfaction leaned the same way — every heavy-slow patient was satisfied at twelve weeks against 80% of the eccentric group — but that gap fell just short of statistical significance and had narrowed by the one-year mark. Time cost tells you why: the eccentric programme came to about 308 minutes a week, the heavy-slow one about 107. (Beyer et al., 2015)

Read that as permission, not a ranking. The best protocol is the one you'll still be doing in week nine, and three short sessions is a schedule. Twice a day, every day, is a hope.

Do you have to stop running?

It's usually the first thing you're told and the thing runners hate most. A 2007 randomised trial tested it directly: 38 people with Achilles tendinopathy, all on the same progressive loading programme. Half were told to stop running and jumping for the first six weeks. The other half were allowed to keep going under a pain-monitoring rule. The two groups improved at the same rate, and the group that kept running showed no negative effects from doing so. (Silbernagel et al., 2007)

The rule they used is worth copying exactly, because "keep running" without it is how people make this worse:

• Pain during and after the run is allowed up to 5 on a 0–10 scale. Above that, you've overdone it.
• The next morning it should still be no higher than 5. Worse than that the morning after means yesterday was too much.
• Week to week, pain and stiffness shouldn't be trending up. If they are, cut back before the tendon makes you.

Inside those lines, running is part of the loading, not the enemy of it. Speed work and hills are where most people cross the line, so those are the first things to trim, not the easy miles.

The protocol, in practice

Single-leg heel raise on a step, slow. Ball of the foot on the edge of a step, rise up, lower until the heel sits below the step, on one leg. Three seconds up, three seconds down. The tempo is the point, and the rep you rush is the rep you wasted. (This is a blend, and worth saying so: the single-leg heel drop off a step is the 1998 movement; the tempo, sets, three sessions a week and the fifteen-to-six progression are the 2015 heavy-slow scheme, which loaded it on gym machines.)

Two versions, every session. Knee straight loads the gastrocnemius. Knee bent — a seated calf raise, or a standing one with the knee softly bent — shifts the work to the soleus, which is doing most of the pushing when you run: biomechanical models put soleus force at roughly six to eight times bodyweight at running speeds. (Dorn et al., 2012) Runners skip the bent-knee version, and it's the one the tendon feels most.

Heavy enough that the last two reps are hard. Start around a weight you could manage fifteen times and, over eight to twelve weeks, work down toward a six-rep load, adding weight in a backpack or holding a dumbbell. Three or four sets, three times a week. The same weight for eight weeks isn't a progression; it's maintenance. (If you use the builder, it starts the calf raises at three sets of ten to twelve and adds a set as each block goes on; the weight on your back is yours to progress.)

Some ache during the sets is normal. Tendons complain while they work, and the 1998 protocol explicitly allowed pain during the exercise, adding weight only once a load had gone quiet. Sharp pain, or a tendon that's clearly worse the next morning, is the signal to take a step back on the weight.

Give it twelve weeks before you judge it. That's the length the 1998 and 2015 protocols ran for a reason. The tendon rebuilds on a slow clock, and the usual way this goes wrong is quitting in the dull middle weeks, not the work failing.

What to keep out while it's angry

Jumping. Pogo hops, skipping, box jumps, bounding, line hops, hill strides. They ask the tendon for fast, high force, which is the right goal for month four and the wrong one for week one. Bring them back in small doses once the morning stiffness has been gone for a few weeks and the heavy sets are quiet.

Aggressive calf stretching. Especially with pain at the heel bone: pushing the ankle into deep dorsiflexion presses the tendon against the bone and tends to stir it up. A tendon that feels tight usually wants strength, not length.

Sudden changes underneath you. New minimalist shoes, a week of hill repeats, a jump in mileage. The Achilles is the tissue that notices these first, so whatever changed in the month before the pain started is the first suspect.

Fitting it into a running week

Three sessions a week, roughly every other day. The heavy sets belong in the full strength sessions, and the placement rules are the same ones that protect every hard run: put them on a day where tomorrow isn't a hard run or the long run, keep the day before intervals or a long run to core-only or light work, make the day after the long run light core and ankle work only, and if your week has a day with no running in it, leave it alone as a full rest day. A tired, heavily loaded calf the day before a tempo session lands badly, and bad landings are how tendons get overloaded in the first place. (The builder bends one of these only when a week leaves it no other slot: then the session lands the day before the long run with every set stopped well short of hard, and it says so on the plan.)

On the days between, the easy runs still count as loading, as long as they pass the next-morning test. You're not choosing between running and rehab. Done in the right order, they're the same programme.

Next read: Plantar fasciitis in runners: why loading beats stretching  ·  Shin splints and strength training: what helps, what to skip

This guide is general information for healthy runners, not medical advice for your situation. A sudden snap or pop in the calf or heel with weakness pushing off, pain and swelling that arrived all at once rather than gradually, pain right at the heel bone rather than above it, a tendon that's hot or red, or pain that keeps failing the next-morning test week after week are all reasons to be assessed by a professional rather than to start a loading program on your own.