Historically, therapeutic exercise has aimed to strengthen or improve the tolerance of previously injured tissue, such as ligaments, muscles, and tendons. While this is undoubtedly important, researchers are beginning to conclude that the physical strengthening of a tissue is only a piece of the rehabilitation puzzle.
A publication in the British Journal of Sports Medicine entitled ‘Tendon neuroplastic training: changing the way we think about tendon rehabilitation: a narrative review’ proposed that traditional treatment of those with tendon injuries has fallen short by treating the tendon in isolation. When compared to their healthy counterparts it was shown that athletes with tendon injury demonstrate greater inhibition of the injured structure in the somatosensory and primary motor cortex – the part of the brain associated with sensation and movement. These central changes act as a potential link between an initial injury, and re-injury either at the same location or in the opposite arm or leg. Changes in the brain are thought to influence the biomechanics of walking, jumping, and other movements of daily living. Put simply, the control of movement in those with tendon injuries is thought to sub-optimal compared to their healthy counterparts.
These changes to motor control tend to persist even after the painful tendon has physically healed, which explains why those with previous injury are more likely to re-injure long after it has healed. Though it is unclear whether these changes in motor control are the cause of injury or the result of injury, it is clear that they should be addressed when structuring a rehabilitation program.
When performing resistance exercise, regardless of if the context is rehabilitation-focused or not, it is common to use a self-paced strategy when moving through the repetitions. For example, when doing a shoulder press the individual performing the exercise dictates the tempo at which they lift and lower the weight. During a self-paced exercise session, there are no cues to structure the length of time we actually push the weight over our heads or lower them back down. External cues involve the use of a device such as a metronome to provide structure to the tempo of each repetition. The use of external cues that control your timing in lifting and lowering the weight has been shown to cause more excitation in the brain. These are the same areas of the brain that studies have found to be inhibited in those with a tendon injury.
Overall, any exercise we perform can be modified in many different ways, regardless of the intention behind them is; strength, speed, or injury rehabilitation. In addition to the local damage to the tendon, we are beginning to understand that there is a change in one’s motor control of that body part. In order to maximize the benefits that traditional rehabilitation has on these injuries, the use of an external cue such as a metronome could be used while performing traditional rehab exercises. This helps to not only physically strengthen the injured tendon, but helps improve overall motor control, and subsequently may reduce the risk of future tendon injury. For healthy individuals, metronome training forces you to truly control the exercise throughout its entire range of motion and can be a great way to make any exercise more difficult.
In the video below, Dr. Andrew Sauer demonstrates a bottoms-up kettlebell press which is made more difficult with the use of a metronome. A metronome can be used as an external cue to influence the tempo and control at which you perform an exercise. Give it a try and if you are interested in learning more about the use of external cues in exercise, check out Dr. Sauer’s blog post where he summarizes the impact a metronome can have on motor control and rehabilitation.
Rio E, Kidgell D, Moseley GL, Gaida J, Docking S, Purdam C, Cook J. Tendon neuroplastic training: changing the way we think about tendon rehabilitation: a narrative review. Br J Sports Med. 2016 Feb 1;50(4):209-15.