Tendons can be tricky to treat. Any athlete that's experienced tendinopathy will know they can be slow to improve and easy to aggravate. Despite recent developments in tendon rehab a number of patients remain somewhat unresponsive to conservative treatment and recurrence rates of tendinopathy are high, even after treatment. Those of us with a particular interest in tendinopathy are always looking for better ways to help our patients, so it's exciting when a new concept is brought to the treatment table. The latest concept, hot off the press, is Tendon Neuroplastic Training, or TNT…
Ebonie Rio (@Tendonpain) and a great team of tendon experts have developed the concept on Tendon Neuroplastic Training (TNT) which they've introduced in an open access paper published in the British Journal of Sports Medicine. It builds on current thinking to improve motor control as well as improving tendon load capacity.
What is current thinking?
Until fairly recently eccentric only exercises (like heel drops) have been the mainstay of tendon rehab. Many clinicians still stick quite closely to the Alfreson protocol from the late 90's but tendon research has moved on somewhat since then. Eccentric rehab may well still have a role but isometric exercise has been introduced to reduce pain and Heavy Slow Resistance (HSR) training is arguably the first choice at present for building strength and load capacity.
What do you mean by load capacity?
Tendons are subject to a lot of mechanical loading during running. A recent study found the achilles tendon to take 6-7 times body weight during running;
Source: Almonroeder et al. (2014)
Tendons are part of a muscle-tendon unit, working together to absorb load and behave like a complex spring during running. This unit needs the ability to manage the load it's exposed to, this is what we mean by load capacity.
Recently Jill Cook and Sean Docking built on this theory in their great paper on tissue capacity which we've discussed in detail here. They suggest that not only do we need to think about the load capacity of local tissues but also consider the capacity of the entire kinetic chain. For example, for a runner with achilles tendinopathy it's likely we'll want to strengthen the calf muscles to improve local load capacity and other muscles which may help manage the load during sport and daily activities. The quadriceps are thought to be the largest contrubitor to absorbing load during running (Hamner et al. 2010) and the gluteal muscles assist them. It might make sense then to strengthen these muscles too to improve the load capacity of the entire kinetic chain. Thorough assessment would hopefully identify other muscle groups and other factors, beyond just strength, that might be relevant for load capacity;
What does TNT add?
Previous approaches to tendinopathy focus on building strength and load capacity, Tendon Neuroplastic Training adds improved motor control. Cortical inhibition has been reported to be a feature of tendinopathy (Rio et al. 2015). In simple terms this means the area of the brain that controls the muscle (the motor cortex) isn't functioning properly. It needs to find a balance between excitation and inhibition and in tendinopathy this balance is thought to be altered. TNT adds external pacing to tendon rehab exercises using a metronome to improve motor control and help restore this balance.
This addition makes lots of sense from a purely practical point of view. Heavy Slow Resistance training is meant to be done slowly (the clue's in the name!). A contraction speed of 3 seconds for the concentric component, followed by 3 seconds for the eccentric has been used successfully in tendon rehab (Kongsgaard et al. 2009 and 2010, Beyer et al. 2015). Using a metronome is a great way of facilitating this contraction speed. If it's also able to improve motor control as suggested then it makes a lot of sense to add this to current tendon rehab.
Tendinopathy is an exciting area for research at the moment with a host of new papers this year. However it is also fair to say we need more research for several key areas. To my knowledge Heavy Slow Resistance training has only been tested in 3 studies, and only with the patellar and achilles tendons to date. Isometric exercise has become a key feature in tendon pain management but this is based largely on one study of just 6 patients. TNT is an exciting concept and it highlights the importance of considering the brain and central nervous system in injury management. However it is, at present, largely based on work that is yet to be published. That said, much of that work appears to have been submitted or in review so hopefully we'll see this concept develop nicely in the near future.
It's very easy of course to say, “more research is needed”, much, much harder to actually produce that research! Writing a blog gives a nice platform from which to ciritique the evidence but it does also mean we have a relatively easy life! We get to criticise the research without having to produce any of it or be subject to peer-review. I've come to realise this by getting involved in research myself and submitting work to a journal.
So, while we may acknowledge we'd love more evidence, we should also acknowledge the amazing amount of work Ebonie Rio and her colleagues have done in describing tendon pain (Rio et al. 2014) in demonstrating the effects of isometric exercise (Rio et al. 2015) and in introducing this new concept. And I'm sure there's much more to come!…
Closing thoughts: Tendon Neuroplastic Training is an exciting new concept that builds on previous tendon research. It involves using a metronome to externally pace rehab exercises and can be used as part of an active self-management programme. While more research is needed to test this concept it fits nicely with current thinking and could be a useful tool for managing painful tendinopathy.