Next in our series is an injury that I am very familiar with, Achilles tendonitis. This popped up back in 2020 or so, when I started getting more serious about running and was hiking every weekend. It's something that I notice here and there still. But I don't let it affect me, and never let it stop me. Here's how to manage and fix it:

If you’re a hybrid athlete, you already know your Achilles tendons aren’t just along for the ride—they’re the springs that keep you moving. They load, store energy, and explode every single stride. They help you sprint the HYROX sled pull, bound over a Spartan wall, and keep your long runs smooth.

And when they’re injured? You feel it everywhere.

Achilles tendonitis is one of those injuries that doesn’t just slow you down—it messes with your head. You can lift, row, ski erg, maybe even bike, but the second you think about running again you wonder: Will this flare up?

The good news: you can come back stronger than before if you follow the right progression. The key is patience, progression, and respecting the tendon’s need for gradual loading. Today I’m walking you through a return-to-running framework for Achilles tendonitis—from zero running to fast intervals (yes, even those brutal HYROX race pace repeats) and everything in between.

Step 1: Respect the No-Running Phase (But Don’t Just Rest)

Most people make one of two mistakes after Achilles tendonitis:

1. They keep running through it until they can’t walk.

2. They “rest it” for weeks, lose fitness, and the tendon is no better when they try again.

The reality is tendons don’t heal with rest. They need load—but the right load.

During the no-running phase:

• Double down on heavy strength training (calf raises, RDLs, split squats, trap bar deadlifts). Aim for 3–5 sets of 6–8 reps at a challenging weight. This builds the tendon’s load tolerance.

• Add isometric calf holds (30–45 seconds, 4–5 rounds) to reduce pain sensitivity. Start with these.

• Swap running with low-impact cardio like cycling, rowing, or ski erg to keep your aerobic base alive. At least temporarily if you can't handle it. If you can, then drop the mileage for a bit, and slow down on your runs. Slower pace means less impact, less impact means less discomfort (hopefully).

Think of this phase as building the foundation for your tendon to earn running again.

Step 2: Reintroduce Running with Walk-Run Intervals

Once you can do heavy calf work pain-free and walk briskly without irritation, it’s time to test the waters. Don’t jump straight into a 5K run. Instead, start with walk-run intervals.

A simple progression looks like this:

• Week 1: 1 min jog / 2 min walk × 10 (20–30 min total)

• Week 2: 2 min jog / 1 min walk × 10

• Week 3: 5 min jog / 1 min walk × 6

The rule: no pain above a 3/10 during, and no increase in pain the next day. If it spikes, back off and repeat the previous step.

This isn’t about fitness—it’s about reconditioning the tendon to handle repetitive ground contact again.

Step 3: Build the Aerobic Base with Easy Mileage

Once you can run continuously for 30 minutes pain-free, it’s time to build your aerobic base. Hybrid athletes often skip this step because they’d rather live in the pain cave, but here’s the truth: your aerobic base is what makes everything else possible.

A 2015 study in the Journal of Strength & Conditioning Research showed that low-intensity running improves tendon stiffness and overall running economy. In other words, easy miles don’t just build cardio—they build resilience in the tendon.

How to do it:

• Add 2–3 easy runs per week, starting at 20–30 minutes.

• Gradually build your long run to 60–75 minutes at conversational pace.

• Stay strict: easy means easy. If you’re breathing hard, you’re doing it wrong.

This base work sets the stage for faster intervals later. Skip it, and you’re asking for a relapse.

Step 4: Add Strides and Controlled Speed

Before you hit race-pace intervals, you need to reintroduce faster running in short, safe doses. Enter: strides.

Strides are accelerations over 60–100 meters at ~80% max effort with full recovery. They teach your tendon how to handle speed and elasticity without overwhelming it.

How to progress:

• Start with 4 × 60m strides once per week after an easy run.

• Build to 8 × 100m strides twice per week.

• Keep them smooth—this is about mechanics, not racing.

If you can do this consistently without pain, you’re ready for real speedwork.

Step 5: Reintroduce Interval Training (HYROX Prep)

Hybrid athletes don’t just need to jog forever—we need to suffer through race-pace intervals. But here’s the mistake: jumping straight into sled-push pace 1Ks after an Achilles injury. That’s asking for trouble.

Instead, start with shorter, faster intervals with full recovery before layering in sustained efforts.

Progression example:

• Phase 1: 10 × 200m at 5K pace, 200m walk/jog recovery.

• Phase 2: 8 × 400m at 10K pace, 200m jog recovery.

• Phase 3: 6 × 800m at threshold pace (around 10-mile pace).

• Phase 4: 4–6 × 1K at race pace with equal recovery (HYROX prep).

Layer this into your training once or twice per week, alongside your aerobic base runs. Always monitor tendon response the next day.

Step 6: Race-Specific Demands

By now, you’ve got mileage, you’ve got strides, and you’ve got intervals. The last step is integrating race-specific demands. HYROX isn’t just running—it’s running under fatigue after heavy work. That means your Achilles needs to handle running after sleds, lunges, and wall balls. Especially sleds.

How to prep safely:

• Brick workouts: 500m run → sled push → 500m run × 4.

• Compounding fatigue sessions: Long run with strides at the end.

• Mixed modal conditioning: Row/bike intervals mixed with running.

These workouts mimic the demands of race day without overwhelming your tendon in one shot.

The Role of Strength Training

Here’s the part most runners overlook: heavy strength training is your best weapon against Achilles tendonitis coming back.

Why? Because tendons respond best to heavy, slow load. A 2018 review in British Journal of Sports Medicine confirmed that heavy strength training improves tendon structure, pain, and function in Achilles injuries. Heavy strength training also improves running economy and reduces injury risk.

Key lifts to keep in your program:

• Heavy calf raises (straight leg + bent knee)

• Split squats / Bulgarian split squats

• Trap bar deadlifts

• Hip thrusts / glute bridges

These aren’t “accessory” exercises—they’re your armor. Do them consistently, even when you’re running pain-free. The key word here is "heavy." It needs to be challenging and heavy enough to build these adaptations. I like to provide education when performing these activities using RPE, at least at 7-8. Not max effort, but a very good effort.

How to Know You’re Ready

In the early phase of recovery, having a few benchmarks is key. Here's what I use:

• Do 30 full range single leg calf raises pain free.

• 15 single leg hops pain free

• Jog for 30 mins pain free

If you can do these three things, then you're on the way back to full running pain free.

Final Thoughts

Coming back from Achilles tendonitis isn’t about rushing. It’s about building—step by step—until your tendon can handle everything you throw at it. Start with no running, earn your way back with strength, then layer in walk-runs, base mileage, strides, intervals, and finally race-specific workouts.

The goal isn’t just to get you back to running. It’s to make you better than before—stronger, faster, and more resilient. Achilles tendonitis doesn’t have to be the injury that sidelines you for good. It can be the injury that forced you to rebuild smarter.

And when you toe the line at your next HYROX or Spartan, you won’t just be “back.” You’ll be ready. If you don't feel like you're ready and need more guidance, book your call with me here.