Research Review By Gary J. Maguire©

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Date Posted:

December 2010

Study Title:

The Role of Motor Learning and Neuroplasticity in Designing Rehabilitation Approaches for Musculoskeletal Pain Disorders

Authors:

Boudreau SA et al.

Author's Affiliations:

Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Denmark.

Publication Information:

Manual Therapy 2010; 15; 410-414.

Background Information:

As we have discussed in prior reviews (see Related Reviews below), many injuries can lead to sustained “plastic changes” within the nervous system that can change not only the pain experience, but functional recovery and response to treatment. Cortical neuroplastic change is a key neurophysiological feature that is correlated with the level of functional recovery following cortical, spinal or peripheral injuries.

One example of the clinical application of this concept is in stroke rehabilitation programs that utilize an approach called constraint induced therapy (CIT) (1). This treatment approach is focused on physically constraining the unaffected limb, requiring patients to utilize their affected limb. This strategy has been associated with marked cortical neuroplastic changes in the affected hemisphere leading to successful functional outcomes for stroke patients. In this scenario the rehabilitation efforts attempt to maximize the extent of cortical neuroplastic changes, thus providing the greatest potential for rehabilitation success.

While these strategies are well established in neurological rehabilitation, they have yet to be fully incorporated into motor rehabilitation treatment approaches for musculoskeletal pain disorders.

Patients with musculoskeletal pain versus healthy individuals have changes (reorganization) of the neuronal properties in the sensorimotor system representing the muscles most affected by pain. In studies with patients with low back pain (LBP), for example, there is evidence of reduced cortical drive in the lumbar spinal muscles and a shift in the representation of the lower back muscles in the somatosensory cortex.

As a clinical example, a recent study has shown that LBP patients who participate in a motor-skill training regime showed a reversal of the location of the center of gravity (CoG) towards that previously demonstrated for healthy individuals and a reduction in self-reported pain (2). These findings suggest that the cortical neuroplastic changes associated with pain may be reversed by motor-skill training.

This narrative review discusses the role of novel motor-skill training in the rehabilitation of patients with musculoskeletal pain. The aim is to highlight key components of motor-skill training that stand to provide the greatest potential for rehabilitation services.

Pertinent Information:

  • Cortical neuroplasticity and recovery of function: Cortical neuroplasticity can be defined as an intrinsic neurophysiological feature that adapts dynamically throughout one’s life. It is a morphological or functional change in neuronal properties, such as strength of internal connections, altered representational patterns or a reorganization of neuronal territories. These cortical neuroplastic changes have been associated with altered motor function or novel motor-skills as well as in the presence of experimental or chronic pain. When considering novel motor-skill acquisition, cortical neuroplastic changes are often accompanied by behavior deemed advantageous (i.e. an increase in motor performance). In contrast, with experimental or chronic pain, neuroplastic changes often result in unfavorable adaptations such as a decrease in performance. Altered motor performance may be a factor for the maintenance of pain. With this factor motor rehabilitation approaches aimed at re-establishing normal motor strategies are a fundamental aspect of treatment of musculoskeletal pain disorders. The ability to promote cortical neuroplastic changes may serve as an indicator for the level of functional recovery. What is important to note from recent studies is that the representation of the muscles affected by pain are altered in the sensorimotor system, that the extent of cortical neuroplastic changes is correlated to the level of motor function (recovery and deficit) and, most importantly, that the level of ongoing pain and the associated cortical neuroplastic changes may be reversed by sensory and motor task training.
  • Motor-skill training: When evaluating novel motor-skill training in healthy individuals, in contrast to passive assistance or repetitions of general exercise, the evidence suggests an associated improvement in task performance and increased representation of the skill-trained muscle in the primary motor cortex. Psychophysical studies involving time scales of neuroplastic changes have demonstrated that the acquisition of a motor-skill follows two stages: first, an early, fast learning stage in which considerable improvement in performance is observed within a single training session and second, a later, slower learning stage in which further gains in performance can be observed across several sessions (and even weeks) of practice.
  • Optimizing rehabilitation success: Motor-skill training coupled with strength training does not promote greater cortical neuroplastic changes in the motor cortex than motor-skill training alone. The ability to target a specific component of movement requires greater skill and increased levels of attention and precision, rather than contraction of all muscles. Emphasis needs to be placed on skilled or precise tasks in order to facilitate the cortical neuroplastic changes that are known to occur in association with the learning stages of untrained functional tasks – this will ultimately lead to improvements in motor behavior or performance. Research that has examined the effects of acute experimental pain have revealed that, as with novel motor-skill training, pain can rapidly alter the excitability of the primary motor cortex. Additional research though is needed to discern the features of the cortical neuroplastic changes associated with novel motor-skill training and that which occurs in association with experimental or chronic pain. In contrast to the rapid changes associated with novel motor-skill acquisition, the changes in cortical excitability that occur in association with acute pain are not necessarily consistent for the muscle groups represented in the motor cortex. It has also been demonstrated that acute experimental pain can suppress the rapid increases in cortical excitability of the motor cortex and interfere with the incremental gains in task performance that would otherwise occur in association with a single-session of novel task training in humans (in this particular study the task involved the tongue [3]). In addition, findings from animal studies have revealed that experimental pain interferes with the neuroplastic changes that underlie simple instrumental learning (condition and response) at the level of the spinal cord.
  • Quality versus quantity: A detailed analysis of the motor behavior associated with novel motor-skill training has revealed that significantly different within session gains in an initial motor-skill training session do not differentially influence the time course of the initial or overall motor performance in subsequent training sessions (time course of these gains in overall motor performance were similar in protocols which consisted of 72 or 144 task-repetitions over a period of 15 and 30 min., respectively). The findings from these studies provide evidence that extended within-session task-repetitions of a novel motor-skill may not facilitate additional gains in overall motor performance. This may be due to rapid changes in cortical excitability being already apparent following short within-session task-repetitions over a period of 10-15 minute training intervals.

Clinical Application & Conclusions:

A common clinical approach that has been shown to be effective in the management of musculoskeletal pain disorders involves training the activation of a delayed or inhibited muscle with repeated isolated voluntary contractions. The rationale for using this approach is based on the principle of novel motor skill training, which places emphasis on improved performance of a movement component rather than the simple execution of a sequence of movements.

Research and clinical application involving motor-skill training should typically be performed in a pain-free manner in order to optimize success. The type, load and frequency of exercise should be tailored towards the patient to accomplish this. Novel motor-skill training should be advocated upon the first presentation of pain symptoms so as to reduce the risk of further and unfavorable neuroplastic changes that are known to occur in association with pain.

Emphasis needs to be placed on slowly increasing the complexity of the novel motor-skill task over the duration of rehabilitation training. This may encourage cognitive effort and enhance the cortical neuroplastic changes that are known to occur in association with novel motor skill acquisition.

Current clinical and experimental findings suggest that quality motor-skill training that encourages cognitive effort should be performed with a limited number of task-repetitions so that fatigue and pain are minimized in order to optimize the outcome of rehabilitation of patients with musculoskeletal pain.

Study Strengths / Weaknesses:

The study provides a clear understanding of how cortical neuroplastic changes provide a key neurophysiological feature that tends to correlate with the level of functional recovery. Successful rehabilitation efforts need to maximize cortical reorganization, and the popularity of such ‘motor control’ approaches is consistently growing. The review provides numerous examples of various novel task examples which were not detailed in this review for clinicians who may want to incorporate these techniques into their rehabilitation practice.

Additional References:

  1. Kunkel et al. Constraint-induced movement therapy for motor recovery in chronic stroke patients. Archives of Physical Medicine and Rehabilitation 1999; 80 (6): 624-628.
  2. Tsao et al. Driving plasticity in the motor cortex in recurrent low back pain. European Journal of Pain 2010; Feb 22 [Epub ahead of print].
  3. Boudreau S, Romaniello A, Wang K, Svensson P, Sessle BJ, Arendt-Nielsen L. The effects of intra-oral pain on motor cortex neuroplasticity associated with shortterm novel tongue-protrusion training in humans. Pain 2007;132(1-2):169e78.