Tuesday 6th February 2018

Exercises shown to not correct abnormal muscle activation patterns

Summary

Most movements require the co-ordinated contraction and relaxation of numerous muscles.  The neurological control of this is known as a muscular activation pattern (MAP).  Previously summarised research describes how highly prevalent latent (pain free) myofascial trigger points (MTPs) alter MAPs producing dysfunctional movement and joint control.  This increases stress on tissues, increasing wear and increasing the risk of injury and impingement syndromes.  Treatment of MTPs was shown to normalise the MAPs.

Research published in the Journal Manual Therapy describes an abnormal MAP found in patients with neck pain, which causes dysfunction the authors hypothesise may increase adverse loading on sensitive cervical structures.  Subjects with this abnormal pattern were each given one of two different six-week supervised exercise programs.  Both exercise programs produced a reduction in pain, but neither changed or corrected the abnormal MAP.

The trial

Subjects
58 females with moderate neck pain of greater than 3 months duration.  Exclusions were previous neck surgery or participation in a neck exercise program in the previous 12 months.

The exercise programs
Exercise programs were conducted over a six-week period.  Participants received weekly supervision and instructions from an experienced physiotherapist.  One regime was described as “endurance-strength training” while the other was described as “low load training of the cranio-cervical muscles”.  Exercises were performed so as not to provoke neck pain.

What was measured
According to the authors, previous work had identified that patients with neck pain demonstrated a bilateral increase of sternocleidomastoid (SCM) muscle electromyography (EMG) amplitude, and a decreased ability to relax their neck muscles after the completion of a task.  EMG readings were taken of the SCM muscles bilaterally.  Pain and disability were also determined using a tool called the Neck Disability Index.

The results

  1. Both regimes resulted in a reduction of pain.
  2. Neither changed or normalised the abnormal SCM activation.

Clinical implications

What the research shows us

  1. Altered MAPs have been shown to cause dysfunctional movement in both the shoulder and neck.
  2. The treatment of MTPs was shown to normalise abnormal MAPS
  3. Exercise was shown to not normalise abnormal MAPs
  4. There was speculation that MAPs became abnormal due to pain.  However, the reduction of pain failed to change the abnormal MAPs

Serious questions about exercises to remedy pain syndromes
The need for exercises as part of rehabilitation is well understood.  However, lets consider at what actually happened during this trial.  Subjects were shown to have an abnormal MAP.  It was hypothesised that the resultant abnormal movements produced would increase adverse loading on sensitive cervical structures.  Subjects in this in this dysfunctional state were instructed to do exercises, which according to the researcher’s hypothesis would place even more adverse load on the sensitive cervical structures. 

After six weeks of placing extra load on those sensitive cervical structures pain had reduced but function was still abnormal.  What would the consequences be of continuing to do this?  Surely it would include rapid degeneration and an increased risk of injury.

Guidelines for rehabilitation
The need for exercise as part of rehabilitation is understood.   However, the implications of dysfunction should be recognised.   The goal should be to perform exercises using correct function.   It is possible to instruct patients in “correct techniques”, but much of the function is determined at a subconscious level involving “pre-programmed” patterns, proprioception and so forth.  

Put simply, it appears that MPTs and other factors that will be considered in future summaries interfere with these “pre-programmed” proprioception based patterns.  Practitioners should focus on remedying these to allow the body to function normally and the body to perform rehabilitation exercises in the normal correct manner.

Don’t take all research at face value
Both exercise regimes were shown to result in a decrease in pain.  Had the MAP issue not been concurrently addressed the research would have supported the use of exercises alone for neck pain sufferers, despite the fact that it doesn’t correct a key problem and would probably result in long term degeneration and an increased risk of injury.

Reference

Falla, D., Jull, G. and Hodges, P. (2008) Training the cervical muscles with prescribed motor tasks does not change muscle activation during a functional activity. Manual Therapy13 6: 507-512. 

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Several years ago Dr Graeme, a Chiropractor practicing in Victoria, Australia was looking for a serious hand held massager his patients could use at home to get the extra quality massage they needed. The ones he found in the shops and on-line for home use looked nice but were not serious, and ... read more