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Foot & Ankle8 min read · Dr. Nevin Saju, PT, DPT
The short answer
Often, yes. Most Achilles pain is a capacity problem, and research shows runners who keep training within clear pain limits recover as well as those who stop. Judge each run by how the tendon feels the next morning, and build calf strength. A pop or being unable to rise onto your toes means stop and see a doctor.
“It's stiff for the first few steps every morning.”
That's usually the first thing runners tell me about their Achilles. Then: “It goes away after a mile.” So they keep running. The next morning it's stiffer. They take a week off, ice it, stretch it, and it calms down.
Then the part that brings them in: “Every time I build mileage, it comes back.”
If that's your pattern, you're not doing anything wrong by wanting to keep running. You just need better rules for how.
Can I run with Achilles pain?
Often, yes. In a randomized trial, runners with Achilles tendinopathy who kept running and jumping, guided by clear pain limits, recovered just as well as runners who stopped, without losing fitness.
The rules come from what's called the pain monitoring model. Research supports keeping pain during the run at no more than about 5 out of 10, letting it settle by the next morning, and making sure pain and morning stiffness aren't creeping up week to week.
The next morning is the real test. Judge the run by how your tendon feels when you get out of bed the next day, not by how it felt during the run. Research shows a tendon's response to heavy loading takes up to about three days to play out, which is why the morning after tells you more than mile three ever will. If morning stiffness is worse than usual, yesterday asked for more than the tendon could handle.
Why not just rest? Tendons don't need rest. They need the right dose. Rest makes the pain quiet and the tendon weaker. Research shows complete rest can cost a muscle 6% to 40% of its force over 4 to 6 weeks, and it lowers tendon stiffness and capacity. Then you go back to your normal running, and the tendon meets the same load with less to handle it.
There is one situation where you stop: a pop, a feeling like you were kicked in the back of the heel, or not being able to rise onto your toes. That's a same day doctor visit, not a running decision.
Your body isn't broken. It just can't handle what you're asking of it yet.
Tendons don't need rest. They need the right dose.
Why does my Achilles feel better once I warm up, then keep coming back?
Because the warm up hides the problem for a while. Research shows Achilles stiffness and pain typically ease during light activity, then return hours later or the next morning. “It feels fine once I warm up” is the trap. The bill comes the next morning.
It keeps coming back because pain fading isn't the same as the tendon being ready. In one study, only 4 out of 16 people whose Achilles pain had fully resolved had actually restored full calf and tendon function on testing. The pain left. The capacity didn't come back with it.
Research points to a handful of common drivers:
- Mileage spikes. Training errors, mostly rapid jumps in volume or intensity, are linked to 60% to 80% of Achilles tendinopathy cases. I break this down in why running injuries keep coming back when you build mileage.
- Hills and speed work. Both put more demand on the calf and Achilles than easy flat running.
- Shoe or stride changes. Switching to a midfoot or forefoot strike adds about 48 times body weight of extra Achilles load per mile compared to landing on your heel. A sudden change in shoes can shift load too. More on how you run in is a running gait analysis worth it.
- Calf capacity. Research shows people with Achilles tendinopathy do fewer single leg calf raises and produce less power on the sore side. A weaker calf leaves more work for the tendon.
- How your foot moves. Pronation is normal. It's how your foot absorbs shock. Research shows pronation on its own doesn't predict injury, but when the foot stays pronated longer, along with the knee drifting in and the hip dropping, load on the Achilles goes up.
- After an ankle sprain. A previous ankle sprain or lower leg injury can change how your ankle moves and increase load on the Achilles. Limited ankle bend is a known risk factor.
Achilles flaring every time you build back up?
How I look at it
Where I'd start
When a runner comes in with Achilles pain, I don't start at the tendon. I start with two questions.
First, how does your foot meet the ground and leave it? I want to see your foot settle onto three points, your heel, the base of your big toe, and the base of your little toe, then roll off cleanly to push. If you stay up on your toes or on the outside edge of your foot, the Achilles tends to pick up the slack. Try this: stand on one leg and feel for those three points, like you're gently squashing an orange under your midfoot. Can you keep your big toe down without your knee locking back?
Second, how does your calf hold up when it gets tired? The number of calf raises matters, but so does what happens on the last few. Watch whether your heel stops rising as high, or whether you start leaning forward to finish. If the sore side fades earlier than the other side, that's where the work is.
That's my starting point, not the whole picture. Everyone's entry point is a little different.
What to do this week
Test your calves, adjust how you run, load the tendon on purpose, and let the next morning guide you.
1
Test your calves.
Stand on one leg with a straight knee and do slow single leg calf raises, one second up and one second down. I look for 30 on each side before calling an Achilles ready for full training. Most runners with Achilles pain can't get close on the sore side, and some can't on the “good” side either.
2
Change the run, don't cancel it.
Keep runs flat and easy, pause hills and speed work, and hold your mileage steady instead of building. Don't switch to a forefoot strike to “fix” it. That adds load to the Achilles.
3
Load the tendon on purpose.
On sore days, some runners find heavy calf raise holds calm the pain: rise up and hold for about 45 seconds, five times. Research on this is mixed, so treat it as an experiment. If it doesn't help you, skip it. On other days, do slow calf raises, three seconds up and three seconds down, adding weight as it gets easier. If your pain is right where the tendon attaches to the heel, do these on a flat floor instead of letting your heel drop off a step.
4
Use the next morning check and the traffic light rule.
If morning symptoms settle within a day or two, keep going. If they hang around 3 to 4 days, scale volume down. Don't stop completely. More in the traffic light rule for training with an injury.
5
Space out your hardest days.
Give your tendon 2 to 3 easier days between heavy loading sessions, whether that's a long run, a hill session, or heavy calf work.
If you want a plan built around your running, that's what physical therapy for runners looks like here. You can also see more on foot and ankle physical therapy and read what other runners have said.
| What you notice | What to do |
|---|---|
| Stiff first steps that ease within minutes | Keep training, and watch whether morning stiffness is stable or creeping up week to week. |
| Feels fine once warmed up, then stiffer the next morning | Yesterday was too much. Cut volume or intensity, and drop hills and speed for now. |
| Pain climbs during the run past about 5 out of 10 | End the run there and scale back your next one. |
| A pop, a kicked in the heel feeling, or can't rise onto your toes | Stop. See a doctor the same day. |
When to see a doctor first
Get evaluated by a physician right away if you have:
- A sudden pop or the feeling of being kicked in the back of the heel
- Being unable to push off or rise onto your toes on that leg
- A visible or felt gap in the tendon
- Pinpoint tenderness on the heel bone, pain at rest or at night, or severe pain putting weight on that leg
- Swelling, warmth, redness, or tenderness in one calf
- Fever, chills, unexplained weight loss, or a history of cancer
- New Achilles pain after starting a fluoroquinolone antibiotic. Talk to your doctor before you keep running.
If anything here needs imaging or a physician, we say so and coordinate it.
Common questions
How long does Achilles tendinopathy take to heal?
Research shows clinical improvement often comes within 6 to 12 weeks of consistent loading, with full recovery commonly taking 3 to 6 months and sometimes up to a year. The timeline depends on how long it's been going on and how well the load is managed. Pain often fades before strength fully returns, which is why testing matters.
Should I stretch my Achilles?
Only if your ankle bend is limited, and even then it won't build the capacity your tendon needs. Stretching something that's already overloaded doesn't give it more capacity. If your pain is at the heel attachment, aggressive stretching can actually irritate it. I explain why in stretching isn't fixing your tightness.
Is my Achilles going to rupture?
Running within clear pain limits hasn't been shown to raise rupture risk. Research links rupture mainly to steroid injections near the tendon, fluoroquinolone antibiotics, and sudden explosive loading after a long layoff. That's one more reason building back gradually beats resting and then jumping back in.
Why did my Achilles start hurting after an ankle sprain?
A previous ankle sprain or lower leg injury can change how your ankle moves, including how far it bends, which shifts more load onto the Achilles. Rebuilding ankle mobility and calf strength after a sprain helps the tendon share that load again.
Keep reading
Revenant Physical Therapy
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Written by
Dr. Nevin Saju, PT, DPT
Founder of Revenant Physical Therapy in Farmers Branch. Three open-heart surgeries taught him what it takes to trust your body again. Now he helps runners, lifters and active adults do the same. More about Nevin →
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