Achilles Tendinopathy: Why Loading Beats Rest for a Sore Heel Cord

A stiff, sore Achilles for the first few steps out of bed is one of the most common complaints we see from North Shore runners, hikers, and anyone who has ramped up their walking on the trails too quickly. The instinct is to rest it until the pain stops. For most people, that is the slowest road back.

Here is what Achilles tendinopathy actually is, why loading the tendon works better than resting it, and what a realistic recovery looks like.

What Achilles tendinopathy is

The Achilles is the thick cord that connects your calf muscles to your heel bone. Tendinopathy is the term for a tendon that has been overloaded faster than it could adapt, which leaves it sore, sometimes thickened, and sensitive to load. It is not usually an inflammatory problem in the way a fresh sprain is, which is part of why anti-inflammatory approaches alone tend to disappoint.

The hallmark is morning stiffness and pain in the first steps of the day or at the start of activity, which often warms up and then returns afterward. The pain sits either in the body of the tendon a few centimetres above the heel, called mid-portion tendinopathy, or right at the heel attachment, called insertional tendinopathy. Telling those two apart matters, because they respond to slightly different loading.

Why rest is the wrong tool

A tendon is living tissue that responds to the demands you place on it. Load it sensibly and it adapts and tolerates more. Take the load away entirely and it does the opposite, getting weaker and staying just as sensitive. That is why so many people rest for weeks, feel fine walking around, then flare straight back up the first time they run.

Rest can have a place in the very early, highly irritable phase, where we strip back the most provocative activity for a short window. But the goal is never to wait out the pain. It is to get the tendon loading again at a level it can handle, then build from there.

Loading is the active ingredient

The treatment that has the strongest track record for Achilles tendinopathy is progressive calf and heel-raise loading. This line of work goes back to the eccentric heel-drop programs studied in the late 1990s and has been refined since into heavy slow resistance, where you load the calf through both the lifting and lowering phases with a controlled tempo and a weight that is genuinely challenging.

The principle is the same one behind every credible tendon program, and we use it for other lower-limb tendons too, as in our guide to patellar tendinopathy and heavy slow resistance. The tendon gets better when you give it a reason to.

In our clinic, an Achilles plan usually starts with calf-raise loading set at a level you can manage, paired with a hard look at what overloaded it in the first place. For most runners that is a spike in volume, a jump in hill or trail work, or a change in footwear. Fixing the input is often half the result.

Mid-portion versus insertional, and why it changes the plan

For mid-portion tendinopathy, loading that takes the tendon into a stretched position, such as heel drops off a step, is generally well tolerated and often helpful. For insertional tendinopathy, where the pain is right at the heel, those deep stretched-position drops can compress the tendon against the heel bone and make things worse. So we keep the loading in a flatter range early on and progress more cautiously.

This is one of the main reasons a generic set of heel raises pulled from the internet often stalls. The right program depends on where your pain actually is, and that is something a physiotherapist confirms at assessment.

How much pain is okay

People are often surprised that we allow some discomfort during loading. The guideline we use is straightforward. A mild ache during or shortly after loading that settles by the next morning is acceptable and does not harm the tendon. Pain that climbs day to day, or morning stiffness that gets steadily worse over a week, means the dose is too high and we back off.

The same logic applies to running. Many people can keep running through Achilles rehab at a reduced volume, as long as pain stays low during the run and calms within 24 hours. We do not insist on stopping running unless the tendon is too irritable to tolerate it, which is similar to how we handle a return to load after other lower-limb injuries like a calf strain returning to running.

What a realistic timeline looks like

Achilles tendinopathy is often slow. Many cases improve over three to six months of consistent loading, and a tendon that has been sore for a year before anyone touched it can take longer. That timeline frustrates people, and it is exactly why the false promise of rest is so appealing. Resting feels like doing something, while it quietly lets the tendon decondition.

We pace the program to the tendon, not the calendar. Early on we set a tolerable load and reduce the worst aggravators. As the tendon settles, the load increases and the running volume comes back gradually. Later, the program rebuilds the specific demands of your sport, whether that is trail hills, sprint work, or simply longer easy runs.

We reassess against function, your calf strength, your single-leg heel-raise capacity, and your tolerance to running, rather than pain alone. Pain is a noisy signal in tendons, and chasing it day to day leads people to stop and start in a way that never builds tolerance.

When to get it assessed

Most Achilles pain is a straightforward tendinopathy, but a few patterns deserve a proper look before assuming that. Sudden, sharp pain with a sense that something snapped, especially with a gap you can feel in the tendon or sudden weakness pushing off, can signal a tendon rupture and needs urgent assessment. Pain with significant swelling, redness, or warmth, or pain that does not fit the usual morning-stiffness pattern, is also worth ruling out.

If your Achilles has been stiff and sore for a few weeks and rest has not fixed it, that is the typical story, and loading is almost certainly the answer. Book a 30-minute appointment and we will confirm whether it is mid-portion or insertional, screen what overloaded it, and build a loading plan that fits your running.

This article is general information about Achilles tendinopathy. It is not personal medical advice. A regulated practitioner can confirm whether the patterns described apply to you.

Sources

• Alfredson et al. — Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis, American Journal of Sports Medicine (1998)
• Beyer et al. — Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: A Randomized Controlled Trial, American Journal of Sports Medicine (2015)
• College of Physical Therapists of BC (CPTBC)