Achilles Tendon RehabilitationTendon Talk: Why the Achilles Matters So Much for Runners

For runners, tendons are everything. They don’t just connect muscle to bone — they store energy, release it, and make running efficient. And no tendon does this more than the Achilles.

The Achilles tendon is the most heavily loaded tendon in the human body. With every step you take while running, it manages forces estimated at six to eight times bodyweight. Its job isn’t simply to tolerate load, but to behave like a spring — stretching, storing elastic energy, and recoiling to propel you forwards.

That’s also why it gets into trouble so easily.

Tendons aren’t passive structures

For a long time, tendons were thought of as inert ropes. We now know that isn’t true. Tendons are living, biologically active tissue. Their cells (tenocytes) constantly sense mechanical load and respond by adjusting collagen structure, cross-linking, and stiffness.

But — and this is crucial — tendon adaptation is slow.

In adults, much of the Achilles tendon’s collagen framework was laid down in childhood and adolescence. What remains is a relatively small, slow-turnover system responsible for day-to-day maintenance. This means tendons don’t adapt at the same pace as muscles or cardiovascular fitness. You can feel fitter long before your tendon is actually ready.

This mismatch is one of the most common reasons runners develop Achilles pain.

Why rest alone doesn’t fix Achilles pain

When pain flares, the instinct is often to rest completely. While short-term load reduction can settle symptoms, prolonged unloading has consequences.

Even brief periods of reduced loading can lead to:

• Reduced collagen synthesis
• Reduced tendon stiffness
• A drop in tendon “quality” — even if tendon size looks unchanged

This explains why runners often feel worse when they return after a break. The pain may have settled, but the tendon’s capacity has quietly dropped in the background.

Tendinopathy is a structural issue, not just inflammation

In Achilles tendinopathy, the tendon doesn’t simply become “inflamed”. Instead, we see:

• Disorganised collagen
• Increased water content
• Changes in stiffness and load tolerance

Importantly, pain does not always correlate with the degree of structural change. Some runners have significant imaging changes with little pain, while others experience pain with relatively minor visible changes. This is why rehab decisions should be guided by function and load tolerance, not scans alone.

Why loading is still the cornerstone of Achilles rehab

The most consistent finding in tendon research is this:

Appropriately dosed mechanical loading is the primary driver of tendon health.

It’s not about whether exercises are eccentric, concentric or isometric — it’s about:

• Load magnitude
• Time under tension
• Progression over time

Heavy, slow calf loading improves tendon stiffness and collagen organisation. Faster, more elastic loading later helps restore running-specific energy storage. The key is progression — and patience.

Where shockwave therapy fits

Extracorporeal Shockwave Therapy (ESWT) doesn’t replace loading — but it can support it.

Shockwave acts as a mechanical stimulus at a cellular level, helping to:

• Increase local blood supply
• Stimulate tenocyte activity
• Promote collagen turnover and remodelling

In chronic Achilles tendinopathy, ESWT can help “wake up” a tendon that has become biologically sluggish. However, like loading, dose matters. More energy is not better, and poorly dosed shockwave can irritate tissue rather than support recovery.

Used well, ESWT can act as a biological primer, making the tendon more responsive to the mechanical loading that follows.

The big picture for runners

Most Achilles problems aren’t caused by weakness or damage — they’re caused by load mismatch.

That mismatch might come from:

• A sudden increase in mileage or intensity
• Speed work or hills layered onto an already fatigued system
• Returning too quickly after rest or injury
• Strong muscles pulling on an under-prepared tendon

The solution isn’t avoidance. It’s intelligent exposure.

The key takeaway

Shockwave can help prepare the tendon.

Loading reshapes it.

Time allows it to adapt.

When runners understand this, Achilles rehab becomes less frightening — and far more effective.