Achilles tendinopathy: why rest does not fix it

It almost never starts with a bang. It starts as stiffness in your first few steps out of bed that eases after a minute on the bathroom floor. Then it becomes a soreness in the tendon that fades a kilometre or two into the run. Then one day it stops fading.

At that point most people do the thing that feels most sensible. They stop running and wait. It usually does feel better that week. Then they start running again, and within a few weeks everything is back. That pattern is not bad luck. It follows directly from the fact that both the popular name for the problem and the most common response to it point the wrong way.

The word tendonitis sends you the wrong way

NHS inform puts the two names side by side on its patient page: Achilles tendinopathy, sometimes known as tendinitis. The two endings mean genuinely different things. The ending -itis means inflammation. The ending -opathy just means a disorder of the tissue. The literature shifted towards tendinopathy because surgery and tissue samples kept turning up degenerative change in the tendon rather than inflammatory cells.

Sweden's national health service puts the same point even more bluntly on its equivalent page. It says the condition means repeated small injuries to the Achilles tendon, and that it is not really an inflammation at all.

That distinction is practical, not linguistic. Inflammation is something you damp down. Repeated small injuries to a tendon are something that has to heal, and tendon tissue heals by being loaded. The two things call for opposite responses. As long as you carry the word tendonitis around in your head, you will keep reaching for offloading, ice and anti-inflammatories, which are three tools built for a different problem.

Rest is not a treatment

This is the most important claim on the page, so it needs evidence rather than opinion.

In a randomised trial published in The American Journal of Sports Medicine in 2007, 75 patients with long-standing midportion Achilles pain were allocated to one of three approaches: eccentric loading, repetitive low-energy shockwave therapy, or an explicit wait-and-see policy (Rompe et al, PMID 17244902). Every patient had already failed at least three months of other management. At four months, 60 per cent of the eccentric loading group reported that they were completely recovered or much improved. In the shockwave group it was 52 per cent. In the wait-and-see group it was 24 per cent. The function scores told the same story, rising from 51 to 76 with loading, from 50 to 70 with shockwave and from 48 to 55 with waiting. The authors concluded that wait-and-see was ineffective.

NHS inform says the same thing in a single sentence: Achilles tendinopathy does not improve with rest, so it is important to keep up as much of your normal daily activity as you can.

Note what that does not mean. It does not mean carrying on with the exact weeks that gave you the problem. It means that backing off is a temporary adjustment to the dose, never a plan. A tendon left alone for six weeks is, six weeks later, a weaker tendon facing the same load that broke it in the first place.

Where does it hurt? Two problems with one name

Before you do a single heel raise, work out where the pain sits. Pinch the tendon between thumb and forefinger, working down from the calf, and find where the tenderness is.

The split is not academic. A prospective cohort study followed 3,379 registered recreational runners for a mean of 20.4 weeks (Journal of Sport and Health Science, 2024, PMID 36963760). Four point two per cent developed a new Achilles problem during that window. Of those, 63.8 per cent were midportion and 27.7 per cent were insertional, with the remainder a combined type.

One note about that paper. In the highlights of the original publication the two figures were the wrong way round, so that the insertional type appeared to be the more common one. The journal issued a corrigendum. The figures above follow the results section of the study, which is the corrected direction.

Why does it matter to you? Because the classic rehab prescription, heel raises performed over the edge of a step so the heel drops below the level of the step, was worked out on midportion cases. Patients with insertional problems were specifically excluded from the trial the programme below comes from. For an insertional problem, the same exercises are usually done with the foot flat on the floor, without dropping the heel below the level of the forefoot, because that deep position compresses the tendon against the heel bone. If you are not sure which one you have, that is exactly the sort of thing a physiotherapist settles in five minutes.

The pain rule: how much is it allowed to hurt?

Here is the single most useful thing on this page, and it comes from a Swedish research group. Karin Grävare Silbernagel and colleagues at the University of Gothenburg published a randomised trial in 2007 in which 38 patients with Achilles tendinopathy were allocated to two groups (The American Journal of Sports Medicine, PMID 17307888). Both followed exactly the same rehabilitation programme. The difference was that one group was allowed to keep running and jumping throughout, guided by a pain-monitoring model, while the other had to stop those activities for the first six weeks.

The model has three rules. As described in the paper:

• Pain was allowed to reach level 5 on a scale where 0 is no pain and 10 is the worst pain imaginable, during the exercise.
• Pain after the session was also allowed to reach 5, but had to have settled by the following morning.
• Pain and stiffness in the tendon were not allowed to increase from week to week.

The third rule is what makes the first two safe. A 5 that has gone by breakfast tells you the tendon worked. A 5 that has become a 6 next week tells you the dose is too high. What you are actually following is not today's number but the direction over time.

The result: no difference in the rate of improvement between the groups. Both improved clearly. Function scores went from 57 to 85 in the training group and from 57 to 91 in the rest group at the twelve-month follow-up. The authors concluded that no negative effects could be demonstrated from continuing to load the tendon with running and jumping while the pain-monitoring model was used.

Read that conclusion exactly as it stands. The study does not show that running heals a tendon faster. It shows that you probably do not have to choose between getting better and staying active, which for most of us is the question that actually matters. The difference between shelving your running for six weeks and keeping it in a scaled-down form is often the difference between coming back and never restarting at all.

The loading programme in four stages

The rehabilitation programme used in Silbernagel's trial is published in full. It is worth looking at closely, because it reveals something most do-it-yourself attempts miss: the stages are governed by what you can do, not by which week it is. Each one has an entry condition.

Four things are worth pausing on.

The stages overlap. Stage 3 begins in week 3 while stage 2 runs to week 5. Progression in a tendon is not a relay where one runner hands over to the next. You shift the emphasis forward while keeping what already works.

The first weeks contain no added weight at all. There is a widespread belief that tendon rehab is about loading heavily straight away. Stage 1 in this programme is circulation work and heel raises with your own body weight on a flat floor. Weight arrives in stage 3, so week three at the earliest, and only once the entry condition is met.

Frequency drops as load rises. Stages 1 and 2 run daily. Stage 3 puts the heavy work on two to three sessions a week. Stage 4 is two to three sessions in total. The heavier the work, the more room the tendon needs between sessions.

The last stage has no end date. The maintenance stage runs from week 12 to six months, with the note in the study that it should carry on for longer if needed. A tendon that has been troublesome once is an area you keep loading even when it stops hurting. Which exercises earn their place in a running stride is covered in the guide to strength training for runners, which also gets into how heavy the heavy part really needs to be.

Two studies, and a striking detail about age

Almost everything written for a general audience about tendon injuries assumes a young athlete. This particular research area is an exception, which is worth knowing if you are over forty.

The modern eccentric approach was described in 1998 by Håkan Alfredson and colleagues (The American Journal of Sports Medicine, PMID 9617396). Fifteen recreational athletes with long-standing symptoms did heavy-load eccentric calf training for twelve weeks. Their mean age was 44.3 years. All fifteen were back at their pre-injury level with full running by the end. A comparison group of fifteen people with the same diagnosis had been managed the conventional way, meaning rest, anti-inflammatories, changes of footwear and physiotherapy. Not one of them was helped, and all were eventually operated on.

In Silbernagel's trial the mean age was 44 in one group and 48 in the other, with a range from 30 to 58.

In other words, the two studies underpinning how Achilles problems are treated today were done on people your age. That is unusual, and it means you can take the numbers at face value instead of mentally adjusting them, which is rarely possible with research done on 22-year-old sports science students.

The Alfredson study should be read for what it is: fifteen participants, no randomisation, and a comparison group that was not randomly assigned. It opened a field rather than settling a question. The later evidence is stronger. A randomised trial from 2015 compared classic eccentric training with heavy slow resistance training in 58 patients and found both worked equally well, at twelve weeks and at one year (Beyer et al, PMID 26018970). So the point is not that eccentric work is magic. The point is that loading works.

Can I keep running?

Often yes, on three conditions.

1. The pain rule applies to every session. Up to 5 during the run, gone by the next morning, no upward creep across the weeks.
2. Cut the dose before you cut the pace. Halve the time before you slow down. A short easy run loads the tendon less than a long easy run. Speed work, hills and anything with a hard push-off wait until you are into stage 3.
3. The strength work is the treatment; the running is what you are protecting. That order must not get reversed. The heel raises are not something you do afterwards if there is time.

If you are someone who runs to work, your dose is fixed by the map, which is a genuine complication because the distance cannot simply be halved. The practical fix is usually to keep one direction and take transport the other, or to build a walking stretch into the middle. How that kind of fixed-route dose gets managed around a working week is covered in the guide to run commuting.

How long does it take?

Longer than you want. It is fairer to know that at the start than to be disappointed in week five.

NHS inform is direct about it: managing Achilles tendinopathy takes time, in most cases several months or more. The rehabilitation programme above places its maintenance stage between week 12 and six months. Sweden's national health service adds a useful nuance at the other end of the scale, noting that symptoms often settle within a week if you reduce the load, though sometimes it takes longer. That is the early, mild presentation rather than the established one.

So expect months rather than weeks if the problem has been there a while. The good thing about that timescale is that it makes the honest everyday plan the only one that works: two or three short strength sessions a week for six months beats any intensive three-month attempt, because the intensive version never actually happens. That logic applies to habits in general and not just to tendons, and it is worked through in the guide to staying motivated to exercise.

What raises the risk

In the cohort study of 3,379 runners, one finding was far stronger than any other: having had Achilles trouble in the previous twelve months. The odds ratio was 6.47, with a confidence interval from 4.27 to 9.81. Nothing else came close.

That is an uncomfortable number, but it is also a useful one. It says the one risk factor you already know about is the one that matters most. If your tendon hurt last winter, this spring's build-up is not a neutral starting point. It should be planned as a return, not as a fresh start.

The study also found that men were affected more often than women, 5.0 per cent against 2.8 per cent. Among those runners, higher age had a weak negative association with the insertional type specifically (odds ratio 0.97 per year). Do not read that as age being protective: Sweden's national health service states the opposite, that Achilles tendinopathy becomes more likely as you get older.

NHS inform lists the other common contributors: a sudden or gradual change in load beyond your current strength or endurance, long periods standing still, unsuitable or poorly fitting footwear, sedentary time that weakens muscle and tendon, smoking, and conditions such as being overweight, diabetes and inflammatory arthritis.

The thread running through nearly all of those is rate of change rather than total amount. The tendon is not objecting to the fact that you run. It is objecting to running more than it has had time to adapt to. That is also why these problems so often surface after a break, when your head remembers your old form and the tissue does not. What actually fades during time off, and how quickly, is covered in the guide to how fast you lose fitness.

Telling a tendon apart from ordinary muscle soreness

This distinction decides what you do tomorrow, so it deserves its own look.

Morning stiffness is the most reliable signal in that table, because it is hard to confuse with anything else. Muscle soreness hurts when you use the muscle. A tendon problem is stiff before you have used anything at all. The full account of what soreness is, including why it is a poor measure of how good a session was, is in the guide to muscle soreness after exercise.

Pain on the outside of the knee during a run is a third thing again, with its own logic. That one is covered in the guide to runner's knee.

When to get it looked at

We are not a medical service. These are the thresholds the health services themselves set out.

• Your symptoms have not improved after twelve weeks of this kind of advice, or they are getting worse. Talk to a healthcare professional. That is the threshold NHS inform gives for Achilles tendinopathy. If you would rather not wait that long, a physiotherapist is the right first port of call, and Sweden's national health service sets its own threshold much earlier, at one week without improvement.
• You felt a sudden snap or a blow to the back of the leg, and walking normally is difficult. Get urgent medical help. NHS hospital patient information describes a ruptured Achilles as feeling as though you have been hit or kicked in the calf, with sudden pain and uncontrolled movement of the foot afterwards. That is a different condition from the one this page is about, and it needs assessing the same day. Call NHS 111 if you are unsure where to go.
• You develop new tendon pain or swelling during or after a course of a quinolone antibiotic such as ciprofloxacin. The European Medicines Agency's advice to patients is to stop taking the medicine, contact a doctor at once and rest the painful area. The agency notes that tendon injury can appear within two days of starting treatment, but also several months after the course has finished. The risk is higher if you are over 60, have reduced kidney function, have had an organ transplant or are taking a corticosteroid at the same time. Tendon injuries of this kind are rare, but they are among the reasons the use of fluoroquinolones is now restricted.
• Symptoms are getting worse even though you have cut the dose. Book an appointment. It does not have to mean anything serious, but it does mean you need someone to look at the foot.

One reassurance worth stating in the other direction, because the worry is common: Sweden's national health service states plainly that having pain in the tendon does not increase the risk of it rupturing. The pain itself is not a countdown to a tear.

If you want something for pain in the first few days, ask a pharmacist or your GP what suits you. Over-the-counter medicines carry their own warnings and combinations to avoid, and that judgement belongs with someone who knows what else you take.

What the week might look like

A concrete example for someone who has been running three times a week and now has a midportion problem that has lasted a couple of weeks. It is an example rather than a prescription, and it does not replace an assessment.

The important part of that table is not the runs. It is that the heel raises appear on every row during the early stages, and that Sunday has a job to do. Without that reading, the third part of the pain rule, the week-to-week part, is just a nice idea. With it, the rule becomes something you can act on.

Common questions

Is Achilles tendonitis actually inflammation?

Usually not. NHS inform lists the condition as Achilles tendinopathy, sometimes known as tendinitis, and the ending matters: -itis means inflammation while -opathy means a disorder of the tissue. Sweden's national health service is blunter, saying the condition means repeated small injuries to the tendon and that it is not really an inflammation. The difference is practical rather than linguistic. Inflammation is something you damp down, whereas repeated small injuries to a tendon heal by having the tendon loaded in stages.

Should I rest an Achilles tendon problem?

No, rest is not the treatment. In a randomised trial of 75 patients with long-standing midportion Achilles pain, 60 per cent of the eccentric loading group were completely recovered or much improved at four months, against 24 per cent of the group told to wait and see. The authors concluded that wait-and-see was ineffective. NHS inform says the same, that Achilles tendinopathy does not improve with rest and that you should keep up as much normal daily activity as you can. Temporarily reducing the dose is reasonable; treating rest as the plan is not.

How much should it hurt when I train with Achilles tendinopathy?

Under the pain-monitoring model used in a Swedish randomised trial, pain was allowed to reach 5 on a 0 to 10 scale during the exercise. Pain after the session was also allowed to reach 5, but had to have settled by the following morning. Pain and stiffness in the tendon were not allowed to increase from week to week. The last rule is the important one, because it is the direction across the weeks that tells you whether the dose is right.

Can I keep running with Achilles tendinopathy?

Often yes, if the pain rule is followed. In that trial, 38 patients were allocated either to keep running and jumping under the pain-monitoring model or to stop such activity for six weeks. There was no difference in the rate of improvement between the groups, and no negative effects of continuing could be demonstrated. Cut duration before pace, and save speed work and hills until symptoms have settled. If your pain sits low down at the heel bone, make the decision with a physiotherapist, because patients with that pattern were excluded from the trial.

How long does Achilles tendinopathy take to heal?

It depends how long it has been there. NHS inform says that managing it takes time, in most cases several months or more, and the published rehabilitation programme places its maintenance stage between week 12 and six months. At the milder end, Sweden's national health service notes that symptoms often settle within a week if you reduce the load, though sometimes it takes longer. Expect months rather than weeks if the problem is established.

When should I see someone about Achilles pain?

NHS inform advises talking to a healthcare professional if your symptoms have not improved after twelve weeks of following its advice, or if they get worse. Get urgent medical help the same day if you felt a sudden snap or a blow to the back of the leg and cannot walk normally, since that may be a ruptured tendon rather than tendinopathy. If new tendon pain appears during or after a course of a quinolone antibiotic, the European Medicines Agency's guidance is to stop taking the medicine and contact a doctor at once. One reassurance: Sweden's national health service states that having pain in the tendon does not increase the risk of it rupturing.

Sources used on this page: NHS inform (Scotland) on Achilles tendinopathy, NHS hospital patient information on Achilles tendon rupture, 1177 (Sweden's national health service) on Achilles tendon complaints and rupture, Rompe et al 2007 (PMID 17244902), Silbernagel et al 2007 (PMID 17307888), Alfredson et al 1998 (PMID 9617396), Beyer et al 2015 (PMID 26018970) and the cohort study in the Journal of Sport and Health Science 2024 with its corrigendum (PMID 36963760). This page gives general health information. It does not diagnose anything and does not replace an assessment by a clinician.