How to Train Through Achilles Tendonitis Without Derailing Your Marathon

Marie Whitt
Sep 22
4 min read

You’re in the middle of marathon training.

The mileage is climbing.

And your Achilles starts getting sassy and talking back.

It’s stiff in the mornings, sore after runs, and every runner you know (plus Google) has a different opinion:

“Just rest it.” “Take some Advil.” “Stretch more.”

Sound familiar?

Here’s the truth: most of that advice is outdated.

And following it can actually keep you stuck in the injury cycle longer.

Let me break down the 3 biggest myths about Achilles pain and showing you what actually helps tendons recover so you can keep training strong.

And if you’re ready for a step-by-step plan to fix it for good, grab my free Calf & Achilles Cure Toolkit ,the exact exercises I give my marathoners to stay on the road, not the sidelines.

Let's hop in.

Myth #1: “I need to take extra rest days if I want to recover quickly.”

Let me start out strong:

REST IS NOT TREATMENT FOR TENDINOPATHY.

Here’s the deal: rest feels like the safe answer when your Achilles starts talking back, but tendons don’t heal best when you stop moving.

What matters most is understanding why they’re irritated followed by applying the right kind of load to strengthen them back up.

What you need to know:

Tendons are sensitive to change. Think about all the shifts that can happen in marathon training:

Transitioning from off-season and into peak training
Getting new shoes throughout your cycle and testing out your new race day pair.
Coming back from downtime due to another injury
Piling on mileage, plus adding speedwork, plus hills...all in the same block

That’s a whole lot of change in a short period of time.

No surprise your Achilles can get cranky.

Here’s the key take away I need you to learn: your body’s capacity only matches the loads you consistently put on it.

Meaning, if you drop all your training to “rest,” you don’t just offload your tendon, trying to help it heal. You also lower its capacity, meaning you drop the threshold of "how much work can this tendon do?".

So when you come back and start running again, suddenly the same training load feels heavier and harder because your tendon is at a disadvantage, starting at a new, weaker baseline.

Cue the endless cycle of: more pain → more rest → even less capacity.

That’s the downward spiral so many runners fall into.

Rest alone just digs the hole deeper.

The smarter move? Adjust and progress your training loads WITH the help of running-specific exercises designed to help you eliminate Achilles tendon pain, build a stronger tendon, and restore tendon-tissue capacity while respecting pain signals.

And if you're looking for these exercises, I've got them for you at the end ;)

Myth #2: “I should ice to bring down inflammation.”

Remember RICE? (Rest, Ice, Compression, Elevation.)

That old-school approach is officially outdated. Now, we follow PEACE & LOVE: a framework that emphasizes protection, education, and active loading over passive “shut-it-down” methods.

Here’s why:

Calling it “tendonitis” is actually misleading. “-itis” implies an inflammation process, which isn't actually occuring despite you feeling pain. Instead, what you’re experiencing is tendinopathy, a condition defined less by swelling and more by changes in tendon structure and its load tolerance.

That explains why the Achilles often has a “warm-up phenomenon.”

It typically feels stiff or painful at first, especially in the mornings and loosens up as you move, improving throughout the day with. However, it flares again the next morning.

That 24-hour response window is your best clue into whether your tendon is coping with the loads you’re placing on it.

So this pain...is actually your friend.

Pain isn’t automatically the enemy. It’s your body’s way of giving you feedback.

Instead of thinking “pain = damage,” think “pain = information.”

For tendons, the morning-after symptoms are the real test:

If you have low, stable pain in the morning that doesn’t escalate day after day, that’s a fantastic sign your tendon is handling the load.
If your stiffness or pain spikes the following morning after a running or achilles-calf workout, that means you went too hard for the moment and need to ease off the intensity You did too much, too soon, but it's ok! You can still make a recovery.
If your pain lasts longer than 30 minutes in the morning, that’s a red flag. If it continues and lingers for a week, it's a signal something else could be going on and it's time to check-in with your doctor.

Bottom line?

Ice might feel soothing, but it’s not fixing the root problem. The real solution lies in smart, progressive loading that respects your tendon’s 24-hour feedback loop.

And if you're itching for exercises to do just that and get you back to full-intensity marathon training, I've got your exercise below!

Myth #3: “My Achilles flared up because I didn’t stretch enough.”

This classic completely misses the point.

Stretching might feel good in the moment, but it doesn’t actually treat your tendon.

Why? Because tendons don’t get injured due to a lack of length.

They get injured when you consistently ask them to handle more load or generate more power than they’re currently capable of.

Think about it:

Added hills too soon in your training?
Jumped into plyos or speedwork without a steady buildup?
Doubled down on longer runs to build mileage with inadequate recovery in between?

All of these crank up the demands on your Achilles.

When the tendon isn’t ready for that level of stress, the tissue can become irritated: sometimes through repetitive overload, sometimes through compression at certain joint angles.

The truth is: your Achilles pain has nothing to do with how long or short your tendon fibers are. It has everything to do with whether the tendon is conditioned to handle the workouts you’re throwing at it.

So sure, stretch if it gives you temporary relief. But don’t confuse it with actual solution: building tendon capacity through progressive, smart loading is what actually keeps you training (and racing) strong.

Speaking of which...ready to grab the exact exercises to help you do this?