Wednesday, October 28, 2009

Are your muscles dysfunctional? Understanding Neck Pain: Part 1

   I have always been a firm believer that when it comes to diagnosing conditions one has to find the specific structure causing the pain. However, neck pain is not always so straight forward. To truly understand neck pain you have to embrace the concept that muscles work in synergy together.

   Have you ever looked deeply into the statistics regarding neck pain? If you have you might start to think nobody knows what their doing. Neck pain has been estimated to have reoccurence rates as high as 94% in some studies. This means if you were to get neck pain there is a 94% chance of you getting it again. These numbers pose a valuable question.

How do mechanical neck pain (MNP) sufferers differ then the normal population? 

   There are a number of different entities which separate those which suffer from MNP and those which do not. However, for purposes of this column we will be looking at muscle dysfunction.

    Firstly, what many people may not know is those who experience MNP have been shown to experience physical changes in their muscles. While in pain you often fail to use muscles you once used efficiently. This can lead to changes in those muscles.
    For example, studies have shown whiplash sufferers to actually have a pronounce amount of fatty tissue in their suboccipital and multifidus muscles. These muscles particularly play an important part of proprioception. Proprioception is the necks way of understanding where the head is in correlation to the rest of the body. In addition, those which experience chronic neck pain have muscles which atrophy due to disuse.
    These physical changes may explain the high reoccurrence rate of neck pain. Professionals may be focusing too much on addressing eliminating pain but not on these physical changes in the muscles

     In addition, people with MNP often have been shown to have changes in their muscles behaviours. Your body now finds a way to completely reorganize its muscular activity. Muscles that once worked in synergy together now work at different times.
    There are two main groups of muscles in the neck, global muscles and local muscles. Global muscles which are fairly superficial are used mostly to produce strength, force and overall stability. Local muscles are commonly deeper muscles in the neck. Local muscles are often used for proprioception and stability of the vertebral column. Basically picture local muscles as a sleeve around your vertebral column trying to protect it and keep it upright and stable. Both groups of muscles work to help keep your neck stable. What happens when one of the muscle groups aren't doing their job? The other muscle group takes over and this can lead to overactive muscles and thus pain.

    Studies have exemplified this theory again and again. Those suffering from MNP have been shown to have highly overactive global muscles. Secondly, those with MNP have also been shown to have deep cervical muscles which are inhibited. This means these muscles have a slower reaction time to firing. Such results indicate that the global muscles commonly compensate for the local muscles in those MNP sufferers.

Why is this important?
    Well now that you are using the more superficial muscles (anterior scalenes and sternocleidomastoid muscles) these particular muscles become fatigued quicker than normal. Although, all this happens at the subconscious level it can still be detrimental.
    A great analogy used by Stuart McGill is the example of someone getting back pain while shovelling their driveway in the winter. While shovelling muscles now have to choose between being used for respiration or stabilizing the back. Obviously, they choose respiration and now the person's back may give out or experience pain.

    So now the muscles have physically changed and altered their normal behaviour. This combination can affect a muscle's ability to produce force and function as it once did. Those with MNP have been shown to have deficiencies in maximal strength, endurance, power and efficiency in contracting muscles. What is more interesting is these deficiencies usually are evident in activities which require 20-50% maximal muscle force. This range of force is what most daily activities require. Daily activities like turning your head as you pull out of the driveway, raising your head for a sustained period to do overhead work or even just tilting your head slightly to watch TV.

    In summary, one must truly understand how muscular dysfunction can cause neck pain before attempting to treat it. If you are just focusing on reducing the pain you are simply taking a band aid approach. As professionals we should attempt to not just relieve the symptoms but also incorporate a plan so the symptoms never return. So the next time your neck is in pain try to worry about what's causing it and not the pain itself. Dr. Wayne Button, BSc, D.C

O’Leary, S. (2009). Muscle Dysfunction in Cervical Spine Pain: Implications for Assessment and Management Journal of Orthopaedic and Sports Physical Therapy DOI: 10.2519/jospt.2009.2872