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Completely by chance rather than design I have found myself helping a number of distance runners over the past 2 years to recover from serious achilles injuries that had prohibited them from running for at least 1 year. All of these runners had tried various physiotherapy treatments, worked with different physiotherapists and doctors and all had little to no success before asking for my help. To date every runner that has come to me for help with their achilles injury has recovered 100% and has never had the injury again. Prior to the past 2 years I helped a number of competitive climbers in the same way. They were suffering from the most common overuse injury in climbing, golfer’s elbow. Effectively another tendinopathy issue but just in the arms. Essentially a climbers achilles injury.

Achilles Function

The achilles tendon is the most important structure in the legs for effective and efficient running in my opinion as a coach. Runners who are more elastic generally run faster and for less effort than those who are less elastic. What I term ‘Elastic Efficiency’ is essentially the holy grail of distance runner training and development. Everything we do to physically strengthen the body should be aiming towards this. The reason it is so important is because it is tendonous material and not muscle that makes runners more springy and hence faster for a small metabolic cost. The achilles being the most important spring in the runners body. Whilst it is the calf muscles that initiate what we call the myotactic reflex (the trigger if you like to loading the spring), it is the achilles tendon that reacts to this reflex and compensates for it to complete the critical process we call the stretch-shortening cycle. The effectiveness and efficiency of this cycle is of paramount importance in running. This is a concept that good strength coaches understand extremely well but that medical practitioners by and large I have found don’t generally appreciate well enough.

the critical process we call the stretch-shortening cycle

As the runner accelerates the lower leg and foot at the ground they impart a force into the ground, a force that increases initially as the body’s center of mass moves over the foot and then reduces as the foot pressure is released after mid stance. The applied force is reactively given back to the body via the foot thanks to basic Newtonian mechanics and the runner’s body then attempts to utilize as much of the reaction force as possible to propel themselves forward. The key structures (ignoring for a second the plantar fascia and windlass mechanism) that absorb the initial force and translate it into elastic spring are in the rear (posterior) of the lower leg (combination of the achilles, soleus and gastrocnemius). So the achilles not only absorbs very high forces that are multiple times the runners static body mass but it must also create elastic recoil from them and do this multiple times per second. For a 30-40min run the achilles may have to deal with this task several thousand times. And through each foot strike it will have to lengthen and shorten cyclically whilst under load.

the achilles may have to deal with this task several thousand times


Key Understanding

  • In the majority of cases of achilles injuries in runners where there is no significant associated inflammatory response the repetitive strain placed on the tendon tissue causes breakup of the bonds that bind the individual collagen fibers together. The body’s immediate medical first aid response is to lay down available type 3 collagen to replace the damaged fibers. Normally healthy strong tendons are composed of dominantly type 1 collagen fibers with many bonds holding them together. This type 3 collagen doesn’t have the necessary elastic properties to function correctly in the achilles when under load and acts to break up the continuity of structure of the fibers further weakening the overall tissue. Hence injured achilles tendons don’t stretch and shorten as quickly and smoothly, are structurally weaker and produce stiffness and pain much more easily. Their resilience to repetitive loading is much lower. Equally importantly, because the new type 3 collagen doesn’t bind correctly to the existing type 1 material, vascularity in that area is reduced. This further reduces localized blood flow, hampering further recovery.


  • For optimal functioning of the achilles the runner needs to be able to correctly manipulate the stretch-shortening cycle. When the runner runs too fast for the level of challenge their calf’s and achilles can handle this elastic propulsion system gets overloaded. When the runner runs too slowly and their associated cadence is too low they fight against rather than work in harmony with this natural elastic propulsion system. This is why when I’m helping an athlete recover their achilles injury,  when they run I make sure the pace is neither too fast or too slow. Countless times I have seen runners who are running too slow and with too low a cadence. In short this deliberate slow down of the system increases what we call the amortization phase of the stretch-shortening cycle and compromises the body’s inbuilt natural reflexes.


  • Tendinopathy in general does not improve with rest. Whilst rest may be a good route for recovering other injuries, structures like the achilles tendon do not recover correctly or fully with rest. If there is no evidence of associated inflammation then ice, compression and anti inflammatories will be of little direct help to recovery either. In this case tendon injuries with no associated inflammation are normally described as tendinosis as opposed to the more commonly referenced term tendinitis.


  • Achilles injuries most commonly build up in distance runners over time because the tendon itself has not been adequately trained to be strong and resilient enough to withstand the cumulative load being applied to it. Recalling that we are talking about multiple times body mass, thousands of times per run. I have commonly observed this in runners who are keen to get mileage in each week en route to their goals but aren’t doing anything additionally to help strengthen the structure of their tendons. Achilles issues can also arise from large changes in training volume, training style or training environment. Environment includes footwear. For example a guaranteed classic way to develop a sore achilles is to switch from regular cushioned running shoes to racing flats or track spikes without any transition period.


  • Strength training is the only proven reliable way to improve the physical characteristics of the tendon and recover it back to 100% health. It is also critical to maintain later tendon health such that the injury does not reoccur again in short order. In my own opinion from dealing with runners with this injury I believe the best type of practitioner to execute this kind of strengthening program is a strength coach with a solid understanding of rehabilitation not to mention a deep understanding of running coaching and training.


  • Control of load and cumulative load volume is critical during rehabilitation. From my coaching perspective this means control of cross training workouts and running workouts. Constantly working under the level at which pain is generated is vital. However bringing the runner back to controlled load bearing workouts is key to remodeling the tissue. Supervision of workouts by the practitioner is crucial and making sure the runner maintains emotional control and sticks to the guidelines is critical.


  • In my own personal opinion most of the so-called tendon treatments that are offered by physiotherapists are nothing more than way to reduce pain and/or inflammation. I have seen athletes receive all kinds of fancy treatments with expensive machines and of course there have been those that have had to have numerous injections (i.e. PRP). With the exception of injections that have a history of causing more long term problems than they solve, I believe these are all fine, as long as the runner isn’t paying out of pocket for them, however the long term fix as it were should cost nearly nothing at all as I will detail in the next section on practical aspects.


  • Achilles tendon injuries respond very slowly. Slower than other classic running injuries. Tendons in the body typically receive very limited blood flow compared with muscle tissue. The collagen that makes up the fibers of tendons tends to be slow at being correctly replaced and remodeled. In addition it is often very hard for the recovering runner to avoid weight bearing on their achilles during the normal daily routines. That said recovering an achilles correctly takes time and patience. I have seen runners that have given up after 1 month because they didn’t get the results that they expected to see in that time. And this is the challenge, sometimes there can be very little improvement in the first 4-6 weeks. But I always, always urge the runner to maintain faith and stick with the program. In every case eventually the body will begin to respond after some time and runner can feel some validation that their patient wait was worth it.


  • The tendon isn’t fixed until its fixed. It’s extremely easy for the runner to get excited as the tendon recovers and start to push themselves and start to make up for lost time. But until the tendon is recovered 100% the job is still not done. One over-exuberant week can take the runner right back to ground zero and wipe out months of hard work. In my experience of all the classic running injuries this is the one that really tests the runners mental discipline the most.


Practical Aspects

  1. Strengthening

The proven method for strengthening and remodeling the tissue of the achilles that has been shown to work time and time again and has worked every time for me is eccentric heel drops. They begin with single leg heel drops (double leg to raise back up to the start position) with just body weight and gradually progress to heel drops with additional weight. Studies have shown that to be effective high rep counts are required per session and my own experience absolutely confirms this. 15-30 reps each side just won’t cut it, were talking 100+ each side per session. Technique is everything, the eccentric lower must be smooth and single legged and the return must the smooth and double legged. Poor technique will render the exercise relatively useless

  1. Diet

During the recovery phase research based evidence has shown that gelatin supplementation (5-15g once per day) can significantly increase collagen synthesis in the body helping speed up he recovery and make the recovery more complete. Taking on board high quality casein rich protein such as milk immediately after strength training (approx 1.5-2g per kg body mass) has also been highlighted to help stimulate faster recovery.

  1. Ancillary

Whilst the runner embarks on the prescribed strengthening program I also keep them active with helpful complimentary treatments such as calf muscle massage, contrast bathing and/or ultrasound. None of these directly help the achilles to recover but they tend to help keep the muscles and tendon happy and happy tissues are free to focus on recovery. I also advise the athlete to be careful with how much time they spend on their feet each day and how they support their feet when they sleep. Pushing the top of the foot down into the bed mattress will act to compress the achilles during the night leading to extra soreness in the morning after getting out of bed and initially walking around.


M.Sc, MSci, B.Sc, CSCS, NSCA-CPT, XPS, CGS. Malc Kent is a professional coach, internationally respected applied scientist and former world class athlete that has represented Great Britain 31 times internationally. His services include personal coaching and mentoring, running gait and biomechanical analysis and running strength coaching.

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