Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury

Review written by Mike Studer info

Key Points

  1. Current rehabilitation approaches do not sufficiently target secondary changes in the brain experienced after ACL injury.
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BACKGROUND & OBJECTIVE

After ACL injury there are neuroplastic changes that take place in the brain, on top of the better-known neuromuscular changes in the lower limb. ACL rehabilitation approaches often do not address these secondary changes in the brain. Gokeler and colleagues’ stated purpose for this article was to “…present novel clinically integrated motor learning principles to support neuroplasticity that can improve patient functional performance and reduce the risk of second ACL injury”.

After ACL rupture, both the ipsilateral and contralateral leg are at increased risk of ACL injury.
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Any time that an impairment of the body impacts the motor control choices on a consistent if not lifelong basis – there are bound to be neuroplastic changes.

A single ACL tear impacts more than just the knee The concept that an ACL tear impacts an athlete beyond the injured knee should not be novel. Ipsilateral changes occur in biomechanics, strength and stability. Contralateral changes occur due to compensation and are well-cited. However, it may be a novel consideration to some readers that there are changes at the level of the brain after ACL. These changes are indeed happening in the brain due to the knee injury. Specifically, this includes neuroplastic changes that occur due to pain, experiences (momentary instability), perception (consequences of movement), and resources (endurance, strength).

Known changes in kinematics elevate patient risk Related to the discussion about defining “recovered” and the discussion of diffuse movement system changes, are the well-cited kinematics changes after ACL injury. Specific changes include elevated tibiofemoral contact forces that may directly increase the risk of OA. Additionally, pain, fear and weakness can alter motor control (neuroplastic changes in procedural memories), which in turn can impact hip rotation bilaterally, and increases in both the frontal and sagittal plane motion of the knee during eccentric force absorption as well as postural stability throughout the affected lower extremity (3). These novel and compensatory recruitment patterns acquired in recovery can become “the new normal”, altering motor control (again bottom-up changes) while pain is present – and beyond.

Emerging concepts in motor learning can and should be applied So, what is new in motor control that can be added to ACL-R? What have we been missing? Most importantly, will integrating these concepts make a difference in return to sport or complications (second ACL injury, OA, etc) outcomes? In this article, the authors review four main concepts of motor control that could be better integrated into ACL-R. In summary, these include: Contextual interference: Promoting higher degrees of retention (motor learning vs. performance) by increasing the variation in schedule and context of task practice. Random practice is but one form of contextual interference. External focus of attention: As in sport and life, much of our movement is purposeful and goal-directed, so should our training be. Repetitions focused on an outcome, “put the ball in the upper L hand corner of the goal”, will be more successful in all attributes of learning than, “move your leg like this”. Intrinsic feedback: As people advance, they should supply an increasing percentage of the feedback that they receive (as opposed to external feedback e.g. from you the therapist) – promoting greater self-monitoring and awareness. Autonomy: Most learners will have a greater level of intensity and sustained attention when they have some input on the tasks and goals in the session. These are considered self-controlled and self-directed learning attributes, incorporating greater recruitment of the attention centers in the frontal lobe.

CLINICAL IMPLICATIONS

This notion of bottom-up change (from the knee to the brain) is not exclusive to lower extremity injuries in athletes. It is pervasive in conditions such as diabetic neuropathy, amputation, osteoarthritis, and many more. Consider, any time that an impairment

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