Achilles Pain When Running — Why It Happens & How to Fix It (Without Stopping Your Miles)

Dr. Matt
2 days ago
4 min read

If you’re a runner dealing with calf tightness, heel pain, or that sharp tug at the base of your Achilles—you are not alone.

Achilles pain is one of the top 3 running injuries we treat at Thrive HQ.

And the truth is:

Most runners don’t get Achilles pain because they run too much…They get Achilles pain because they recover too little.

And then—on top of that—they unknowingly run with mechanics that load the tendon 2–3x harder than necessary.

Good news:You don’t need to stop running to fix this. You just need a better strategy.

First, Understand What the Achilles Actually Does

The Achilles isn’t there to just “flex your calf.”

Its actual job is to:

Store elastic energy
Release it with each stride
Act like a spring

It is not designed to be a brake. But most runners turn it into one.

This is why:

The tendon becomes irritated
Calves feel “tight”
You wake up with heel pain or morning stiffness
Pain shows up mid-run or the day after

Those aren’t flexibility problems —they’re capacity problems.

Key Mistake #1 — You ramp volume faster than tissue adapts

Runners are great at building lungs. Terrible at building tendons. While cardio adapts in weeks, tendons adapt in months. So what happens?

You add:

2 extra miles
A hill route
Tempo repeats

Your lungs say “let’s go," but your Achilles is saying “what in the world...?” This is why pain often shows up at weeks 4–8 of training cycles.

Key Mistake #2 — Weak Posterior Tibialis

This is the single most overlooked cause of Achilles pain in recreational runners.

When the posterior tib is weak:

Your foot collapses into pronation
The Achilles becomes a stabilizer instead of a spring
Load per stride skyrockets

A weak posterior tib forces the Achilles to do two jobs—stabilizer AND propulsor—and it’s not built for that.

If you see collapsing arches on video or your shoes tilt inward —this is you.

The Fix:

3–4 sets with 8–10 reps of each:

Split squat calf raises
Eccentric calf raise with toes angled IN
Arch raise + front-to-back scale

Key Mistake #3 — Running form forces too much ankle extension

This comes from:

Overstriding
Low cadence

Every one of these increases ground reaction force at the ankle.

The Fix:

Increase your cadence by 5% weekly (if you are running consistently), until your cadence reaches 180 steps per minute. This is one of the quickest ways to reduce almost all running related pain, as every 5% increase in cadence decreases the ground reaction force by 20%.

Quick Technique Fixes

1️⃣ Increase cadence by 5% (not to 180 — toward 180)

Do not force 180 immediately. As mentioned above, increase by 5% weekly if you are running on a consistent basis. If inconsistent, make sure to get at least 5 runs in with the new cadence before increasing further.

Examples:

If you’re at 160 → target 168
If you’re at 170 → target 178

As your stride shortens the impact force plummets!

2️⃣ Temporarily switch to a heel strike

This offloads the tendon as it heals. It is super important here to mention that this does not mean a midfoot strike or heel strike is "good" or "bad" but rather that each type of strike will increase stress in certain areas while decreasing it in others.

With a heel strike you will decrease the load to the Achilles, shin, calf, and foot BUT will increase the force to your knee and hip joints.

KEY NOTE: if you are switching to a heel strike from a midfoot strike in the middle of a running program, you will want to decrease your volume significantly, as your body will need to adjust to the change in stress from the new technique

3️⃣ Run outdoors if possible

This one can be a bit tricky up here during the MN winter, but the reality is that treadmills increase braking mechanics.

Outdoor surface:

More variability
More natural gait rhythm
Lower ground reaction force

What Runners Try (That Doesn’t Work Long Term)

🚫 Static calf stretching

This "deactivates" the tendon and fails to change mechanics

🚫 Complete rest

Tendon loses capacity, so when you return it flares up

🚫 Buying new shoes

Although this can be a potential solution, we must also fix running mechanic issues for a long term solution

🚫 Massage your calves daily

This will help with treating the symptom, but not addressing the root cause

What Actually Fixes Achilles Pain Long Term

Tendons don’t heal with stretching. They heal with controlled loading.

The research is clear on this one:

Phase 1: Pain modulation

Isometrics
Shortened range
Reduce explosive work

Phase 2: Heavy slow resistance (HSR)

6–8 reps
Long eccentrics
3–4×/week

Phase 3: Power & run-specific loading

Plyometrics
Cadence work
Midfoot mechanics

You’re not trying to make the tendon relax. You’re trying to make it stronger than before.

Want to Finally Become a Pain-Free Runner?

We’re going to be launching the first ever Pain-Free Runner Challenge in early 2026, which will be built exclusively for active runners who want to:

Fix recurring aches (think Achilles, knee, hip, foot)
Get ahead of future injuries
Improve form and mechanics
Build tendon capacity and durability
Run stronger, faster, and injury-free for the long term

💥 This first round is a FREE beta group, and we’re only taking 20 runners.

Why free? Because we’re building this WITH you — and we want feedback from real runners before we open it publicly.

➡️ Join the early access list here👉 https://visit.thrive-hq.com/pain-free-runner-challenge

Apply to Join the Pain Free Runner Challenge

Once the 20 spots are gone, enrollment for the beta launch closes. No exceptions.

Ready to Get to the Root Cause of Your Pain? Choose Your Path!

📞 If you want 1-on-1 clarity immediately:

Book Your Free Discovery Call👉 https://www.thrive-hq.com/speak-with-our-team

🏃‍♂️ If you're training for 2026 and want to bulletproof your running:

Apply for our FREE beta launch of the Pain Free Runner Challenge 👉 https://visit.thrive-hq.com/pain-free-runner-challenge

Apply to Join the Pain Free Runner Challenge