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A Deep Dive into Achilles Tendinopathy

We have covered the topic on Achilles tendinopathy in the past, refer to our previous blog on “All About Achilles Tendinopathy”. Today we look at the injury process, the different types of Achilles tendinopathy and their characteristics, and how treatment may differ from one another.

But first, couple of key points summarized from the previous blog:

  • Every tendon has its load capacity, and its collagen property acts as a spring i.e. when you land the tendon stretches under load and then releases power to propel yourself up.

  • CONTROLLED training load + ADEQUATE recovery = ADAPTATION in its LOAD TOLERANCE

  • HIGH training load + INADEQUATE recovery = PATHOLOGICAL where injury process takes place

Now, Achilles tendinopathy progresses from one stage to the next with each phase marrying up to an increasingly debilitative state.

The Injury Process of Achilles Tendinopathy

Reactive tendinopathy describes the first acute overload (load > tissue tolerance) to the cellular structure where small proteins flood the extracellular matrix manifesting the tendon to become swollen and painful. Note that the swelling is not caused by inflammation. This process is normally reversible if you remove the trigger that caused the overload. However, if the excessive load is not removed, you will progress to the next stage.

Under continuation of overload, there will be more and more small proteins flooding the extracellular matrix causing disarray of collagen fibres. These disorganized collagens then begin to break down and eventually dies off at the end stage of tendinopathy, degeneration. Degenerated part of the tendon does not elicit any pain, thus, the reason why it is difficult to differentiate when the tendon is in disrepair or degeneration. However, the area of degenerated tissue is unable to bear any load, losing its springlike capacity. Think of this as holes in donuts, where the holes are the islands of degenerated collagen and the body of the donut being the normal tendon tissue. The good news is that your body will adapt and grow more normal tendon tissue around these “dead spots” in effort to recover lost strength.

The types of Archilles tendinopathy

There are three types of Achilles tendinopathy when it is overloaded each with differing symptoms and approaches to fix.


This type of injury occurs mainly due to tensile load (a pulling force similar to stretching of a rubber band). When the load tolerance point has been exceeded due to too much volume or intensity of training, the reactive phase can be sparked. Thus, this injury is very common in plyometric training which requires a lot of intense jumping.


  • Localised pain above the calcaneus or heel bone

  • Painful in intense periods of plyometric movements


Unlike the former, this type of injury is localized to the insertional point of the Achilles tendon which is the calcaneus or heel bone. This is mainly caused by both tensile force and compression as seen in many activities such as squatting, lunging, running up the hill or on the beach. These activities all have one thing in common and that is the dorsiflexed ankle under load. When your shin is pulled into a more angled position, it compresses the Achilles tendon against the heel bone.


  • Localised pain near calcaneus or heel bone

  • Painful activities such as squatting, lunging, running up hills or on sand

  • Painful calf stretch

  • NOT PAINFUL with hopping on toes


Not a true tendinopathy unlike its predecessors as the structure involved is the thin sheath that surrounds the Achilles tendon. Pain is created from the constant friction of the Achilles tendon against the sheath during continuous low-load ankle movement rather than an overload of force.


  • Cracking or popping sound/sensation (tendon fails to move smoothly within the thickened peritendon)

The Rebuilding Process

Regardless of which type of Achilles tendinopathy you may have, the first step is always to remove the aggravating factors or activities. For instance, you can simply overload the tendon during one specific workout or due to accumulated strain over several sessions. Thus, this is when you take a step back to get relative rest, NOT complete rest!

The strength of your tendon follows the motto of “if you don’t use it, you lose it.” With complete rest, your tendon’s load tolerance level drops even lower, putting you at a painful start of rehabilitation. On the other hand, if you continue to push through pain and load a painful tendon, the injury will worsen. Thus, this becomes a difficult balancing act and the main reason why so many people end up with chronic, repetitive tendon injuries.

Understanding the characteristics of Achilles tendinopathy become an important part of the rebuilding process and the balancing act. For instance, insertional tendinopathy benefits from having a heel raise insert in your footwear as it unloads the compression of the tendon against the calcaneus.

Before we go through the rehab process, let’s talk about passive treatment and why it doesn’t work. Passive treatment describes something that is done to you. These can include ice, electrotherapy, dry needling, ultrasound, and scraping to name a few. These treatments are often ineffective and short-lived as they do nothing to address the load tolerance level of the tendon.

The Rehab Plan

Phase 1- Isometrics

Isometrics describes loading up the tendon through muscle contraction without any joint movement. This is beneficial early on the rehab as acute pain often stops people from doing the traditional strengthening exercises. Isometric exercise’s main objective is to decrease the pain! This is achieved through inhibiting neural output and activate those dormant motor units that was switched off by pain.

Try performing isometric exercise at 70% of your maximum capability e.g. holding onto a 8kg kettlebell whilst holding a partial heel raise position for 5 sets of 45s hold

e.g. partial heel raise in standing or seated position

Once your pain is down to a 2-3 out of 10 in intensity, it is time to move onto the next stage.

Phase 2 – Isotonics

Isotonic exercises describe movements that require muscles to resist weight over a range of motion, thus, causing a change to the muscle length. This often includes both concentric and eccentric phases in a muscle contraction. As our aim is to improve load tolerance level of the Achilles tendon, it is inevitable that we will return to the classic strengthening exercises. The key to isotonic is to perform the exercise with heavy slow resistance (HSR). HSR allows the person to improve load tolerance level without using the tendon as a spring. Slow tempo means the exercise should be performed ideally for 3s eccentrically and 3s concentrically.

e.g. Seated heel raise with the weight directly over the shin (for video refer to our previous blog on All about Achilles tendinopathy). Standing single heel raise with weight 4 sets of 15 reps

Once the strength of your affected leg is equal to the non-injured leg, we can move onto the next phase.

Phase 3 – Plyometrics

Just having enough strength to perform certain exercises do not mean we have restored ‘the spring’. The next stage before returning to sports or any form of high-level activities such as running or jumping/ landing, you also need to increase the ability of the tendon to absorb and store loads. This is called the stretch-shortening cycle where the Achilles stores and then release energy to generate large amounts of power, and this is where plyometric exercises come in.

Start with a depth drop focusing on landing softly to absorb the force of the impact. If this exercise feels good, move onto a single-leg landing. Then progress onto single-leg hop.

Then progress to double-leg pogo hops. Try 30-50 reps before resting.

At this stage of rehab, try to mix in HSR with plyometric training on a twice to three-times a-week basis. If you ever wonder whether you are ready for running/ jumping or return to play, we offer VALD Forcedeck analysis as it is a good way to measure the amount of peak force generated and see if there is any asymmetry.

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