This article is prepared by LøberLab. LøberLab specializes in evidence-based training and works to optimize runners' performance through the latest research and physiological knowledge.
You might know it. A dull stiffness in the tendon behind the ankle when you put your feet on the floor in the morning. The first minutes of the run feel stiff and sore, but once warmed up, it almost eases. The next day it's back. And even though you've rested, stretched, and taken it easy, it doesn't really improve.
Achilles tendon issues are among the most common injuries in runners, often frustrating because they linger. The good news is that most return to running when they understand what's really happening and focus their efforts in the right place.
What is an Achilles tendon injury really?
Most Achilles tendon issues in runners are what we call a tendinopathy. It's not an acute inflammation, nor a sign that the tendon is "worn out". It's a tendon that has received more load than it currently has the capacity to handle.
A tendon is living tissue that constantly adapts. If you load it appropriately and give it time to recover, it gradually becomes stronger and stiffer, better at storing and releasing energy with each step. If you load it more than it can handle, the balance tips the other way. The tissue starts to react, becomes sore, and its structure changes slightly. You feel the result as stiffness, soreness, and pain at the start.
The important thing to understand is that the problem rarely concerns the tendon alone. It's about the relationship between how much you load it and how much it can currently tolerate. And that's precisely the relationship you can influence.
Why does it occur?
Achilles tendon issues almost always occur because the load has increased faster than the body can keep up. It can be many things at once:
- You've increased your weekly distance or number of workouts relatively quickly.
- You've added more speed or hills, which place extra stress on the calf muscles and tendon.
- You're sleeping too little during a busy period, so recovery can't keep up.
- You've switched to shoes with a lower drop, which demands more from the tendon.
Often it's a combination. A busy week at work, a few short nights, and an extra interval session can together push a tendon that was otherwise coping well over the edge. It's rarely one big mistake. It's the sum of many small things.
The myth of rest
The most common misconception is that the tendon needs rest to heal. Most runners with Achilles issues have done what seems logical: paused, stretched, taken it easy. Yet the pain is still there when they start running again.
The reason is that rest doesn't build capacity. When you completely stop loading the tendon, it actually loses stiffness and strength within a few weeks. So when you return to running, you face the same load as before, but with a tendon that now tolerates less. The problem starts over.
The tendon shouldn't be spared from load. It needs the right amount of load, in the right dosage, so it can adapt and become stronger. This usually means you can continue running through an Achilles recovery, just in a form and amount the body can handle. Running isn't something you should stop. It's part of the treatment.
What about massage, shockwave, and inserts?
When an injury lingers, it's tempting to seek treatments that address the tendon externally. Massage, shockwave, laser, acupuncture, inserts, kinesiotape. Most runners with long-term Achilles issues have tried a few of them.
We're not saying they're worthless. Some can feel nice and provide short-term relief, which can have its place when you need some peace to get started again. But there's an important limitation you should know: none of them build capacity in the tendon. They can ease symptoms for a while, but they don't change the fundamental relationship between what the tendon can tolerate and what you load it with. And it's precisely that relationship that determines if you'll recover.
The reason is physiological. A tendon only becomes stronger when it receives a load it can handle, followed by time and recovery to build up again. It's the actual pull from running and strength training that triggers this building process within the tissue. A treatment working externally doesn't give that signal. It can make the area less sore for a while, but it doesn't create the conditions the tendon needs to adapt and become more robust.
No machine and no treatment can skip that biology. What the right load does to the tendon, neither shockwave, laser, nor a pair of inserts can do instead. Inserts can, for example, temporarily relieve the tendon and ease symptoms, but they don't make the tendon stronger. Therefore, the active part, meaning running and strength training in the right dosage, is always the focal point. Everything else is at best a supplement, never the solution itself.
The way back: a sequence that works
When we help runners return from Achilles issues, we work with a fixed sequence when rebuilding the load: first frequency, then volume, and finally intensity.
| The sequence when rebuilding | ||
|---|---|---|
| Step | How to do it | Move on when |
| 1. Frequency | Short, frequent runs at an easy pace. Walking breaks keep the load down. | Rhythm runs without worsening the next day. |
| 2. Volume | Gradually extend the runs. Still at an easy pace. | Volume holds without reaction. |
| 3. Intensity | Short hill sprints, light tempo changes, progressive finishes. In small doses. | You're back to normal training. |
Frequency first: Short, frequent runs mildly load the tendon each time but allow good recovery time in between. It's an effective way to stimulate the tissue without overloading it. Walking breaks are a strong tool here, as they keep the mechanical load down and allow for more frequent activity.
Then volume: When your body tolerates a steady rhythm without worsening, gradually extend the runs. Still at an easy pace. The goal is to build volume on a stable base.
Intensity last: When both frequency and volume hold without issues, cautiously reintroduce speed. Short hill sprints, light tempo changes, progressive finishes. In small doses, and with close attention to how the tendon reacts.
Speed and hills are what stress the Achilles tendon the most, so they're also the last to be rebuilt. Not because they're dangerous, but because the timing must be right.
How to manage yourself along the way: the traffic light model
One of the most useful ways to navigate is a simple model we call the traffic light. It helps you assess whether the pain you're feeling is acceptable or if you need to dial back.
| Traffic Light Model | |
|---|---|
| Zone | What you feel and do |
| ●Green 0–2 | No or very slight discomfort during running, no worsening afterward, and no extra stiffness the next day. Continue as planned. |
| ●Yellow 3–5 | Slightly increased soreness during running, but it quickly subsides, and the next day the tendon is back to its baseline. Acceptable during rehab. Maintain load, or increase only slightly. |
| ●Red 5+ | Clear pain during orafter running, swelling, or symptoms that worsen and persist the next day. Reduce volume, speed, or frequency. |
Pain scale from 0 to 10, where 0 is no pain.
The key is the reaction the next day. A tendon may make some noise during the run, as long as it's back to baseline the next morning. If it's worse, the load was too much.
Strength training: the part most skip
Besides the run itself, tendons respond well to heavy, slow strength training. It stimulates the tissue to become stronger and stiffer, and for many runners, it's the difference between halfway back and all the way. It's also where you build the capacity that no passive treatment can give you. We've gathered it all in our
.
You don't need to live in a gym. For a busy recreational runner, a couple of short, targeted strength sessions a week can make a big difference. Exercises for calf, ankle, and foot are relevant for Achilles issues, ideally supplemented with something for hip and leg, so the load is better distributed throughout the body. It's about the minimum effective dose, not training as much as possible.
How long does it take?
The honest answer is that tissue takes time, and it can't be rushed. A tendon adapts over weeks to months, not days. However, you can do a lot to ensure the time is used wisely, and you do this by loading smartly rather than waiting for the problem to disappear on its own.
As a rough guideline, a mild, early Achilles issue often improves significantly over a few weeks, while a more established case typically requires a couple of months of targeted work before you're fully back. If it's been going on for a long time, it may take longer. It may sound long, but with the right approach, there's usually progress to notice along the way, and it's that progress you aim for.
When should you seek help?
You can get far on your own with patience and sensible load management. But it's a good idea to get professional help if:
- The pain doesn't improve after a few weeks of targeted work.
- You struggle to find a running volume that doesn't provoke the tendon.
- The same problem has recurred several times.
- You experience swelling, night pain, or sudden severe pain that doesn't fit the usual pattern.
A running-specialized physiotherapist can help you find the right dosage, build a plan that fits your daily life, and ensure you come all the way back instead of getting stuck in the same cycle.
This article is written by LøberLab. At LøberLab, they specialize in working with runners, and their approach is based on managing load and building capacity rather than looking for a single fault to fix.
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