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What type of exercise works for treating Achilles tendinopathy and why? - Isotonic exercises

Updated: Jun 2

Achilles tendinopathy exercise series:


If you do an internet search for exercises for Achilles tendinopathy it uncovers many options and all of these exercises can be used at different stages of the treatment process. The aim of this exercise blog is to understand, according to the latest research, what type of exercise does what, when they should be used and how they can help your recovery. In this article we discuss how exercise with movement (isotonic exercises) can help to restore your muscle power and function, which is essential when rehabilitating a tendinopathy.

What type of exercise works for treating Achilles tendinopathy and why? - Isotonic exercises

In this article:

  • What are isotonic exercises?

  • What do isotonics do?

  • When should I use isotonic exercises for Achilles tendinopathy?

Ali also discusses isotonic exercises in this video:

What are isotonic exercises?

These are exercises with movement (unlike isometric exercises) where the muscle changes its length (lengthens and shortens) whilst under relatively constant tension. An example of this is the classic calf raise exercise associated with Achilles tendinopathy rehab, where you slowly lift yourself up on your toes and then lower yourself down again.

The classic heel raise exercise is a good example of an isotonic exercise for Achilles tendinopathy.

There are different phases to the isotonic exercise and this can simply be broken down into eccentric and concentric movement.

The concentric component is a contraction whilst the muscle shortens e.g. the up part of the calf raise – the calf muscles shorten while lifting you up. The eccentric component is the opposite, the contraction of a muscles whilst it’s lengthening e.g. the down phase of a calf raise – the calf muscles lengthen while lowering you down.

What do isotonics do?

When we injure a tendon and it develops a tendinopathy that tendon loses its capacity to cope with the forces generated by our normal sport. In the case of Achilles injuries, the calf muscles are also affected. This loss of capacity means that, in order for it to recover, your Achilles tendon and calf muscles need to be strengthened.

The anatomy of the calf muscles and Achilles tendon.

A tendon is made of many strands of collagen fibres which are arranged in lots of bundles. Imagine many bundles of spaghetti in parallel with each other. In a tendinopathy, not all the bundles, and indeed not all the fibres in a specific bundle are affected. A lot of them stay healthy.

As with all cells in the body, tendons also follow a natural cycle where old collagen cells in our tendons are replaced by new ones. Exercise promotes this cycle and therefore promotes the creation of healthy collagen – hence why we can use it to strengthen our tendons.

There have been many theories as to what these types of exercises do to help a tendinopathy and there is a history of research papers that take us on a journey through using just eccentrics (the lengthening exercises), isotonic exercises (lengthening and shortening the muscle during the exercises) and also using very heavy weights to strengthen the muscles and resist these movements.

The exact theory of how strength training heals a tendinopathy is unknown. One school of thought is that in some instances the injured collagen fibres are replaced by healthy ones. Another theory suggests that the injured fibres remain injured, but that the new healthy collagen fibres help to support the fibres that are involved in the tendinopathy (like a brace or splint) therefore causing increased strength and function and less pain.

We provide online physiotherapy treatment via video call for Achilles injuries. Follow the link to learn more.

When do I use isotonic exercises for Achilles tendinopathy?

This answer needs to be individualised to you. At we assess you to find your starting point – what is your tendon’s current capacity and what can you do without increasing your symptoms? Our choice of exercises are also guided by your end goal which could be a jog round the block or an Ultra Marathon or anything in between. Other factors such as your general health or medications you take (statins, antibiotics) can also affect what exercises we prescribe and how long it takes to progress.

The main thing to remember is that a decrease in symptoms may not be the first thing you notice when taking up these exercises. An indication that your Achilles is getting better will be the fact that you start to find your exercises easier and that you’re able to progress them. It’s usually only after a few weeks of progressing them that you start to notice a greater reduction in symptoms.

Let us know if you have any questions. Need more help with your Achilles injury? You can consult us online via video call for an assessment of your injury and a bespoke treatment plan.

Best wishes


About the Author:

Alison Gould is a chartered physiotherapist and holds an MSc in Sports and Exercise Medicine. You can follow her on LinkedIn, Facebook, Instagram or Twitter.


  1. Alfredson, H., Pietilä, T., Jonsson, P. and Lorentzon, R., 1998. Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. The American journal of sports medicine, 26(3), pp.360-366.

  2. Beyer, R., Kongsgaard, M., Hougs Kjær, B., Øhlenschlæger, T., Kjær, M. and Magnusson, S.P., 2015. Heavy slow resistance versus eccentric training as treatment for Achilles tendinopathy: a randomized controlled trial. The American journal of sports medicine, 43(7), pp.1704-1711.

  3. Cook, J.L. and Purdam, C.R., 2009. Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British journal of sports medicine, 43(6), pp.409-416.

  4. Silbernagel, K.G., Thomeé, R., Eriksson, B.I. and Karlsson, J., 2007. Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study. The American journal of sports medicine, 35(6), pp.897-906.