Patients and physiotherapists alike struggle to manage tendinopathy and its nasty habit of recurrence. Fortunately, the field keeps evolving and here we’ll discuss a novel approach to tendon rehab called “Tendon Neuroplastic Training”, which targets an often overlooked issue in tendinopathy-motor control.
But First, What is Tendinopathy?
Tendinopathy is a broad term that covers the pain and impaired performance related to overuse of a particular tendon. Most people have heard of “tendinitis” which implies an inflammatory response. However, tendinopathy is a more useful term since there are many ways a tendon can be irritated, which can include degenerative and inflammatory pathways (see Dr. Peter Malliaras’ post for more on this). A whole article could be written on staging tendon dysfunction, so for simplicity we’ll stick with the catch-all term “tendinopathy”.
How Do We Currently Treat Tendinopathy?
Current rehab protocols focus on changing tendon mechanical properties, improving muscle performance, managing load, pain management (i.e. modalities and manual therapy), interventions that affect local tissue (e.g. corticosteroid injection), and changing kinetic chain biomechanics. However, many treatments fail to adequately address the motor control of the muscle linked to the irritated tendon.
Why Focus on Motor Control?
In many tendinopathies there are changes in motor control of the muscle linked to the tendon in question, which can persist, even when pain is decreased and strength is improved (1). One of the main changes is in corticospinal excitability and inhibition, that is, the signals from the motor cortex that excite or inhibit a muscle.
Adapted from: https://commons.wikimedia.org/wiki/File:UMN_vs_LMN.png
For example, a study showed that patients with patellar tendinopathy exhibited abnormal excitability of the quadriceps (1). Normal excitability looks like smoothly ramping up the signal from the motor cortex down to the muscle. However, abnormal excitability looks like little to no signal and then suddenly a sharp spike in the signal to activate a muscle. Think of a driver who shifts from 2nd to 4th gear abruptly, causing the car to jerk forward, versus an experienced driver who smoothly shifts through gears to build up speed.
Curiously, these patients also exhibited increased inhibition of the quadriceps. This means that their brain is limiting the signals from the motor cortex down to the muscle. The net effect has been described by Dr. Ebonie Rio as a driver who has their foot on the gas and brake at the same time (1). This dysfunctional signaling makes it difficult for the muscle to properly respond to the loads placed on it.
So in rehab, we need to normalize this corticospinal excitability and inhibition to restore patients to full function and reduce the risk of recurrence.
How Do We Change Motor Control?
To target the motor control deficits seen in tendinopathy, we can use externally paced strength training. Self-paced exercises have less of an effect on cortical motor control, so just doing more reps with heavier loads will not create the desired changes in motor control. External pacing, on the other hand, has a powerful effect on changing motor control (2).
Enter Tendon Neuroplastic Training (TNT), where we use an external cue, like a metronome, to control the pace of an exercise. For example, rather than performing a heel raise where the patient counts “3 seconds up, 4 seconds down”, in TNT, the patient coordinates their heel raise to a metronome set at 60 beats per minute (bpm), to ensure they are truly working at the desired speed. Once patients try it, many are surprised by how inconsistent their self-paced speed is compared to when they follow the metronome beat.
In addition to improving motor control, TNT keeps patients much more engaged with exercises. How often does a patient perform an exercise and then start gazing around the clinic? Or even forget what rep they are on? The external auditory cue of the metronome creates more engagement in the exercise and keeps patients on task.
How to Implement TNT in the Clinic?
The original protocol described in research by Dr. Ebonie Rio was used for patellar tendinopathy and included an isometric and isotonic knee extension as shown in the table below (1):
|5 sets of 45 seconds||4 sets of 8 reps|
|Patient counts duration of hold with 60 bpm metronome||Patients performs 3 second concentric and 4 second eccentric to a 60 bpm metronome|
Of course, this protocol should be modified based on the person in front of you and their stage of rehab.
For example, for posterior tibialis tendinopathy, we could use a heel raise while squeezing a tennis ball, performing a 3 second concentric and 4 second eccentric phase. In the clinic, I set the metronome to 60 bpm and count the first few reps with the patient, saying “1-2-top” (meaning that they should be at the highest position of the heel raise on the 3rd beat) and then “1-2-3-bottom” (meaning that they should be at the lowest position of the heel raise on the 4th beat). Once the patient understands the pacing, they would complete the prescribed number of reps. Below is an example of how this would look in practice:
As the patient progresses we can use the metronome to quantify and progress the speed of exercise, since rate of loading is a crucial factor in tendon rehab. For example, performing slow, heavy heel raises is great. However, during the gait cycle, the average stance time is just 0.6 seconds, meaning that lower limb tendons must handle fast rates of loading (3). Instead of just saying “do the heel raise faster” we can gradually increase the rate of the metronome beat to approximate the goal activity. Then if appropriate, we can progress to plyometric exercise.
Tendon Neuroplastic Training (TNT) addresses the motor control deficits that come with tendinopathy in a novel way. All you need to get started is a metronome so that patients have an external cue to pace the speed of an exercise. I personally have integrated TNT seamlessly into clinical practice and look forward to seeing more research into its application in a variety of tendinopathies. Its main benefits are that it:
-Improves motor control from the brain down to the muscle
-Can easily be implemented into exercises we already perform in rehab
-Keeps patients highly engaged during exercises
-Lets us quantify and progress the rate of loading of a tendon
- Rio, E., Kidgell, D., Moseley, G. L., Gaida, J., Docking, S., Purdam, C., & Cook, J. (2016). Tendon neuroplastic training: changing the way we think about tendon rehabilitation: a narrative review. British journal of sports medicine, 50(4), 209–215. https://doi.org/10.1136/bjsports-2015-095215
- Leung, M., Rantalainen, T., Teo, W. P., & Kidgell, D. (2017). The corticospinal responses of metronome-paced, but not self-paced strength training are similar to motor skill training. European Journal of Applied Physiology, 117(12), 2479-2492. https://doi.org/10.1007/s00421-017-3736-4
- Murray, M. P., Drought, A. B., & Kory, R. C. (1964). Walking Patterns of Normal Men. The Journal of bone and joint surgery. American volume, 46, 335–360.