Increasing Achilles Load Tolerance – part 2 – The Rebuild

by Greg Dea

*This is part two of a two-part article set, which is wrapped up by Greg’s book, Return to Field Sports Running Manual. The book is available on Apple and Amazon: iBookskindle ebook and paperback.

Click here to read part one first if you haven’t yet seen that one.

Now, I don’t know you personally, but I know you just want a stronger Achilles tendon. If you’ve still got pain – read my previous article. If you don’t, here’s the disclaimer – you could have an Achilles that doesn’t play by the rules I’m going to lay down – so please, make yourself acquainted with a very experienced and highly qualified health practitioner who knows about tendons because there are medical reasons why some tendon issues appear and stick around:

  • Impaired or dysfunctional movement syndromes,
  • Arthritis’s,
  • Gouts,
  • Blood disorders,
  • Use of some antibiotics,
  • Waist to hip ratio – if you’re carrying too much fat you should get tested for Type 2 diabetes and work on losing fat – it is linked to more tendon problems,

So, reloading the Achilles tendon is not as simple as developing strong calf muscles and achieving good ankle mobility. Some of those medical things will need a straight-shooting expert.

There are steps in this journey – skip them if you wish, but don’t miss them. This means if you decide to skip a step, you should know you’ve got the capacity to do the step you’re missing. If you don’t have the capacity to do what you skipped over, you will bear the brunt of the setbacks because they are common when you skip steps. For example, if you don’t complete your Achilles rebuild all the way through strength to elastic loading, you’ll run closer to heel strike and that will inevitably overload your hamstring. I want you to understand how your life will change and what your future will look like as the long night of Achilles-winter comes in. There’s no skipping the night and the dawn can’t be rushed. We’re not going to go deep into the ecosystem of tendon physiology – for most of you that sort of detail is TBU – True But Useless – knowing it isn’t what gets you moving through the night of Achilles injuries. It’s up to us that do know it to guide you through it.

This is how they look.

Stage 1 sees you do the following:

  • de-load the tendon first,
  • maintain strength and movement to offset loss,
  • apply static then slow loads,
  • progress the speed of isolated movements.

Stage 2 will see you shift to whole body loads in patterns of movement instead of isolated movements.

Stage 3 will involve you introducing speed into whole body loaded tasks.

Stage 4 means adding elastic, or springy loads.

In the first part of stage 1, de-load your tendon and get control of the pain as per my previous article, and with a good sports doctor, until your pain is down at around 1/10 – where 10 is a nightmare and 0 is, well, no pain. But, even if your tendon is stubborn and the pain is taking longer than 2-3 weeks to come down that much, don’t rest your tendon longer than 3 weeks. This stage is also about re-loading your muscle to restore some strength and endurance. It’s also about restructuring the tendon in a short position. Stay away from stretching the tendon or loading it at length, for now.

The main fibres of the tendon are made from collagen. One aim of a good therapy program is to restructure the tendon. Collagen is replaced slowly, perhaps taking approximately 100 days (14 weeks)  So, whether you have got pain or not, the tendon collagen gets replaced slowly.

The Achilles tendon is a bit like a grumpy dog. Give the dog some space and time to settle when he or she is upset. To do that with a tendon, apply occasional slow, low impulse movements. These slow, low impulse loads can be applied in a way like calf raises, more correctly heel raises, held for 30-60 seconds, for 3-4 reps, twice each day. The rationale here is to send significant signals to the whole area, maintaining stimulus in a non-elastic way. In the early days, springiness or elasticity is no good – if you load the tendon in a lengthened position, expect to wake up the tendon cells – and when they wake up because of load at length, they vomit – nasty, water-attracting proteins called Aggrecans that cause swelling.

Impatient yet? Let me ease the pressure. If you can do 4 reps of 60 seconds isometric heel raises, on 60 seconds rest, and your tendon hasn’t reacted badly in 2 days, you can progress. Add 20kg, for 4 reps, twice each day. 

If there are no setbacks after 2 days, increase load towards 40kg, then 60kg. This progression can happen in a matter of days,. But, it could also take over 3 months – remember the 100-day rule?

Let’s look ahead a little, towards the dawn. When you do eventually get running on the tendon, most of the time your calf muscles will not behave in running the same as they do in most calf exercises. Most calf exercises involve repeated ankle dorsiflexion and plantarflexion, with concentric and eccentric contractions. In fast running, most calf muscles act with isometric contractions. The feet and Achilles tendons behave more like a spring, tensioned by strong muscles isometrically. So, when you are using your feet and Achilles tendons as springs, the fast twitch (type 2) fibres in the calf won’t be shortening as they contract – they’re going to reflexively hold (isometrically hold) their length under very high stress.

In this early stage of Achilles tendon rehab, you have already done some slow sustained high load isometric contractions to stimulate these type 2 fibres and put some stress on the tendon. However, the tendon will probably not be ready for fast, high load. It would be an increased risk to let the tendon elastically lengthen quickly at this time. Once you’ve been “checked the box” of heel raising 60kg for 60 seconds for 4 reps, you’re going to need to shift away from the type 1 oxygen-breathing endurance-hardy cells to wake up the type 2 glycolytic muscle fibres that will be recruited in running for high intensity bursts at near maximal power. So, you are going to have to do some non-isometric methods – up/downs – to stimulate these type 2 fibres.

I recommend something like 3-4 sets of 6-8 reps (taking 3-4 seconds each rep) of heel raises plus extra weight approaching or up to your own bodyweight, with a partial recovery of up to 30 seconds between sets. For example, if you weigh 80kg (176 pounds), add this weight to your own body and do 4 sets of 8 repetitions of a heel-raise, taking 4 seconds for each repetition, resting 30 seconds between sets.

Frans Bosch is a quietly spoken but exceptionally insightful and successful running coach, professor of biomechanics and motor control – I love his work, but I think he would disagree with this regime perhaps because it is NOT what the pennate fibres of the calf are designed for. These pennate fibres are best designed for isometric bursts, rather than concentric and eccentric work. I agree with him, in running, but since it would be an increased risk to let the tendon elastically lengthen quickly at this time, we need this concentric and eccentric regime to shift the stimulus down from the 60 second isometric efforts in stage 1 while still maintaining a high work load. Let’s do the math: 4 sets of 6 repetitions at 3 seconds per repetition is 72 seconds time under tension – a nice progression on the 60 second isometric holds. I do agree with Professor Bosch that the best stimulus on the calf and achilles tendon is running itself, but when someone is not ready for running and they need a stimulus – this is it.

When you’ve proven your Achilles can handle the above loads, progress again to shorter holds: 1-2 seconds heel raise, higher loads, lower reps again. For example, 2 to 4 repetitions. To keep your time under tension (TUT) high, add more sets. For example, 4 repetitions x 2 seconds x 8 sets = 64 seconds TUT.

To account for the load change, a day on and day off approach is wise.

Practically speaking, these latter stage exercises don’t have to be just heel raises – they could even look like weighted tyre-drags, sled-drags and in the absence of a sled, push a loaded wheelbarrow (eg. 20 to 30 kg) up a short hill. I’ve even packed a rucksack with a kettlebell and walked up short inclines. The incline and the weight of the wheelbarrow mean a 20kg load delivers plenty of stimulus into the body, compared to a heel raise loaded with a load that is close to bodyweight.

Stage 3 is where speed is introduced, but you’ll have to earn the right first. I write extensively about this in my book, Return To Field Sports Running Manual, available as an ebook, iBook and paperback.