Sports medicine research has recently highlighted long-term changes in neurocognitive and central nervous system function among some of the most common ligamentous injuries, including ankle sprain and anterior cruciate ligament tears. Using advanced neurophysiological assessment techniques, researchers have determined that injury induces a functional reorganization of the cortex that results in an altered sensorimotor response, potentially predisposing these individuals to subsequent or repetitive injury.1 However, the clinical implications of these findings have remained ambiguous, thus begging the question of how a practicing sports medicine clinician can recognize these changes and improve these limitations. Therefore, the purpose of this column is to provide guidance to the practicing clinician regarding the effect of central nervous system function in the rehabilitation of a ligamentous injury.
A key consideration regarding central nervous system deficits is that these patients will likely be able to function clinically at the level of their uninjured counterparts. Range of motion, strength, and even functional performance may be within normal limits, yet these patients often remain predisposed to re-injury or self-reported episodes of giving way. Emerging theories suggest that this may be expected because the nervous system adapts to changes by recruiting additional resources throughout the cortex (eg, planning and visual areas) to successfully perform these tasks.1
Dynamic tasks such as running, cutting, and jumping typically only require control from subcortical structures (ie, cerebellum and basal ganglia), whereas such tasks following injury may require the integration of information from cortical structures that would otherwise be used for planning and attention. Therefore, as an individual faces real-world constraints (eg, complex tasks, cognitive demands, and fatigue), the resources to maintain adequate performance or control may no longer be available, leading to altered biomechanics and subsequent injury.2–4 For example, during physical activity an individual may direct attention and focus mainly to extrinsic factors (eg, other players, objective, and environmental conditions) rather than to joint position and movement; however, physical activity following injury may require more attention to movement, making the patient less adaptable to unanticipated changes.
To address these central nervous system alterations, it may be necessary to stress supplementary brain areas within the injury prevention and rehabilitation settings.1,5 Reintroducing motor patterns through exercise to individuals while planning, visual, and other areas of the cortex are facing high demand may force individuals to adopt motor patterns that would be more flexible under extrinsic constraints. From the earliest phases of rehabilitation, cognitive demand exercises could enhance these patterns. For example, exercises emphasizing neuromuscular control and activation may be introduced while the patient performs a serial seven task in which he or she is asked to count backward from a given number by consecutively subtracting the number seven. As rehabilitation advances, the tasks may grow in complexity and be added to functional rehabilitation paradigms.
Many sports medicine clinicians already include several examples of this type of training in their rehabilitation without realizing it. For example, adding a ball toss to single-limb balance exercises forces the athlete to react to an additional stimulus that targets visual constraints and task complexity. We can further increase the cognitive difficulty of the same task with the use of different color balls, requiring the athlete to verbally identify the color of the ball in mid-air. As rehabilitation progresses, choice hopping and reaction tasks in which a cue is given to provide the direction of a cut, hop, or jump may be applicable, thereby forcing the patient to enhance reaction time by processing instruction and developing appropriate motor patterns quickly.
Alternately, the use of visuomotor training, whereby direct or peripheral visual cues are used as a cue for a motor response, could similarly be effective for decreasing reliance on visual areas of the brain.6 The efficacy of this training has been demonstrated using customized software and apparatuses, but could also be achieved with visual cueing systems in which a light-up target serves as a trigger for an exercise or a choice-reaction task. Additionally, in its simplest forms, decreased dependence on visual areas for motor tasks can be achieved through the use of distortive or stroboscopic goggles, allowing for completion of tasks while patients are forced to rely on intrinsic control to achieve those motions.5
Because theories of central nervous system plasticity are only now emerging, the evidence regarding the efficacy of these interventions is scarce and highly varied. The effects of adding cognitive and visual constraints to contribute to task complexity during rehabilitation should be further investigated so that patient-oriented evidence may better guide these decisions.
- Needle AR, Lepley AS, Grooms DR. Central nervous system adaptation after ligamentous injury: a summary of theories, evidence, and clinical interpretation. Sports Med. 2016;47:1271–1288. doi:10.1007/s40279-016-0666-y [CrossRef]
- Rosen AB, Than NT, Smith WZ, et al. Attention is associated with postural control in those with chronic ankle instability. Gait Posture. 2017;54:34–38. doi:10.1016/j.gaitpost.2017.02.023 [CrossRef]
- Song K, Burcal CJ, Hertel J, Wikstrom EA. Increased visual use in chronic ankle instability: a meta-analysis. Med Sci Sports Exerc. 2016;48:2046–2056. doi:10.1249/MSS.0000000000000992 [CrossRef]
- Kim AS, Needle AR, Thomas SJ, Higginson CI, Kaminski TW, Swanik CB. A sex comparison of reactive knee stiffness regulation strategies under cognitive loads. Clin Biomech (Bristol, Avon). 2016;35:86–92. doi:10.1016/j.clinbiomech.2016.04.010 [CrossRef]
- Grooms D, Appelbaum G, Onate J. Neuroplasticity following anterior cruciate ligament injury: a framework for visual-motor training approaches in rehabilitation. J Orthop Sports Phys Ther. 2015;45:381–393. doi:10.2519/jospt.2015.5549 [CrossRef]
- Wilkerson GB, Simpson KA, Clark RA. Assessment and training of visuomotor reaction time for football injury prevention. J Sport Rehabil. 2017;26:26–34. doi:10.1123/jsr.2015-0068 [CrossRef]