In my last article in Oral Health Journal (Feb. 2009), the most common musculoskeletal disorders that dentists encounter were discussed. The impact that these disorders have on the body may be slowed, and in many ways kept at bay, by taking steps at the workplace to minimize their effects. What is required to manage your health and quality of life in the long run however, is to build strong muscles capable of sustaining loads that are encountered daily, at work and play.
This article will focus on low back injury, the most predominant musculoskeletal disorder encountered by dentists. The article will include discussions of the source of low back pain and strengthening exercises aimed at building a foundation to improve quality of life and practice.
Exposure to prolonged static postures and repetitive movements while treating patients creates weakness in the ligamentous structures of the low back. 3,5,9 Ligamentous strain results in increased movement in the already compromised low back and as a result the body compensates using intrinsic and extrinsic muscles to protect the spine. Why does this lead to injury? Load experienced in compromised seated positions will lead to hyperactivation and in some cases under activation of other muscles. 1,5,6 The body responds to unstable joints in the low back with an imbalance among these muscles that are activated with the intent of providing protection. Imbalance begins a vicious cycle of injury, damage, and re-injury. 75% of low back injury recurrence has been attributed to this repetitive injury cycle. 2,3
To understand “recurrence” we must first understand the role of the nervous system in development of low back injury. From a very young age our central nervous system begins to make a motor engram, or blueprint, of how, when, and which muscles should be activated to deliver an intended movement pattern. 2,8,9 Grooving of the motor engram, or pathway of the blueprint, is impacted and disrupted by static postures and muscle imbalance. When groov ing does not occur correctly an optimal pattern of muscle activation is disrupted which subsequently cause muscles to take on loads they cannot maintain. Again, this leads to injury, inadequate compensation, further impact on the motor engram and the vicious cycle continues. Compensation from our body results in as much as 90% recovery from low back pain within the first six weeks post-injury however this lays an important role in a high recurrence rate.
With injury (I will use the term injury to pertain to any disruption to normal kinematics of the human body, which may exist asymptomatically and progress to a symptomatic low back) improper recruitment of muscles leads to delayed muscle activation, decreased muscular endurance and a decrease in pain free
ange of motion. Many individuals at this stage will begin an exercise routine to strengthen their lower back, which is where we may start to do further damage. In many cases the low back scenario worsens during training as we attempt
o strengthen with inappropriate exercise routines that often do not correct motor coordination of agonists and antagonists of a given joint.
The motor engram optimizes our body’s ability to adapt to forces by using agonist, antagonist, and synergistic muscles efficiently to maintain optimal muscle activation. A disrupted motor engram causes our body to respond inappropriately by recruiting muscles to handle loads they are incapable of handling thereby falling in the trap of the vicious cycle.
Muscle imbalance will create inappropriate muscle activation sequences when performing even the most relatively simple tasks such as bending over to pick up a pencil. These motor control errors compromise spinal stability and may lead to brief opportunities for the spine to buckle and develop serious injury. What is required is to re-educate the muscles responsible for low back stability.
This begins with activating the muscles that are intimately related to your spine in the low back. The literature would suggest that the first muscles to be inhibited (stop activating) after low back injury are the Transversus Abdominus (TA) and the Multifidus (MF).2,3,5-9** In fact, the MF muscle has even been shown to undergo fibre type change post injury. After an episode of low back pain MF changes from type 1, a common fibre type found in postural muscles, to a
ast fatiguing type 2 fibre. This change reduces the muscles ability to stabilize the spine. 3
Proper rehabilitation must begin by re-educating the muscles that are activated first before the beginning of any movement (TA and MF).3,5 To effectively rehabilitate the spine after low back injury those muscles close to the spine that are “deactivated” must be “reactivated” before beginning a general exercise program for the low back. The first exercise and technique to master is an abdominal hollowing technique proven to activate both the TA and MF muscles.
After activating the MF and TA you create the normal engram patter providing the opportunity to rehabilitate the muscles around the spine in combination as opposed to over activating some and underacting others, creating the notorious vicious cycle. Performing this exercise should be the first step to a healthy and strong low back. Once you have re-educated the firing pattern within the intrinsic muscles of the low back, you can begin to work on building the strength of your low back with co-activation of the muscles of low back. As Stu McGill depicted in his well documented work, the spine functions similar to a telephone pole. By visualizing your spine as a telephone pole, you can begin to understand that in order to maintain an erect position and hold it steady, it is necessary for taught guy wires to attach to the ground in all directions. A common mistake we make when strengthening our low back is to tighten only a couple of the guy wires while leaving the rest loose. Under these circumstances, it will take substantially less force to knock off or begin to loosen the position of the telephone pole. It is for this reason that when performing strengthening exercises for low back health we need to condition and strengthen the whole ‘orchestra’ of muscles. 3,9
To do this we must perform exercises that challenge muscles in all directions in order to engage the whole ‘orchestra’ of muscles to create the tight guy wires around the spine. 3,9 This is accomplished by bracing: isometrically co-activating all abdominal muscles along with the MF, creating stability in all directions (where only 5-10% of maximum voluntary contraction is required to maintain a stable spine).3,9
From here you can begin to perform the exercises needed to strengthen your low back. Unfortunately, there is no one exercise that challenges all of the abdominal musculature while sparing the low back. However, Canadian researcher Stu McGill has developed three exercises that have been shown to have a great benefit when strengthening the low back… drum roll please! These exercises are now commonly known as the “McGill big three” and include: the bird dog, side plank and modified crunch (pics with explanations). Following a specialized low back strengthening program by a trained professional the incidence of low back injuries and hours lost at work by 50% from 1.09 low back injuries per 200,000 employee hours to 0.52 per 200,000 employee hours. 10
I have put together a sample routine (Table 1). This routine has been developed to help re-educate the muscles of your body in order to create stability around your low back, and to bring about long-term strength, stability and health. Keep in mind this program is only a starting point. Our body after all is an integrated system of muscles and joints that impact and influence each other, from the ankle to the shoulders. Adopting an integrated approach to your exercise training program will increase your chances of long term h
ealth, strength and improve your quality of life. Reeducating your body requires attention by a health professional, don’t compromise your quality of life and health of low back without seeking the consult of a highly educated trainer, chiropractor, or other musculoskeletal specialist prior to beginning any exercise program.
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For further information or comments regarding low back health and the dentist please contact Mahmoud Zaerian, BA Kin, CSCS at info@focusconditioning.com
Oral Health welcomes this original article.
**The multifidus (a muscle that attaches and originates on the vertebrae), transverses abdominus (deepest of abdominal muscles acting like a belt).
REFERENCES
1. Janda V, Vavrova M. Sensory motor stimulation video. Brisbane, Australia: Body Control Systems, 1990.
2. Panjabi MM. The Stabilizing system of the spine. Part 1: Function, dysfunction, adaptation, and enhancement. J Spinal Disord 1992; 5: 383-389.
3. McGill S. Low Back Disorders, Evidence based prevention and rehabilitation. Liberty of Congress Publication, 1997.
4. Panjabi MM, Tech D, White AA. Basic biomechanics of the spine. Neurosurgery 1980; 7:76-93.
5. Altered trunk muscle recruitment in people with low back pain with upper limb movement at different speeds*1, *2. Archives of Physical Medicine and Rehabilitation, Volume 80, Issue 9, Pages 1005-1012. P. Hodges, C. Richardson.
6. Inefficient muscular stabilization of the lumbar spine associated with low back pain: a motor control evaluation of transverse abdominis, Hodges, Paul w., Richardson, Caroly A. Spine, Nov 1996, Vol 21-issue 22, pp 2640-2650.
7. Does strengthening the abdominal muscles prevent low back pain, a Randomized Control Trial, A, Helewa, et al. Journal of Rheumatology 1999;26:1808-15.
8. Deutsch, FE. Isolated lumbar strengthening in the rehabilitation of chronic low back pain. Journal of Manipulative Physiological Therapy. 1996 Feb; 19(2): 124-33.
9. Cholewicki J, McGill SM. Mechanical stability of the in vivo lumbar spine: implications for injury and chronic low back pain. Clinical Biomechanics. 1996;ll:l-15.
10. The effect of Workplace Based Strengthening on Low Back Injury Rates: A Case Study in the Strip Mining Industry. Vert Mooney, et al. Journal of Occupational Rehabilitation, Vol 5, No. 3, 1995.
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When performing strengthening exercises for low back health we need to condition and strengthen the whole ‘orchestra’ of muscles
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Unfortunately, there is no one exercise that challenges all of the abdominal musculature while sparing the low back
