February 2010 Newsletter from Malik Slosberg, DC, MS

Why do Some Patients Keep Hurting Their Back? Evidence of ongoing back muscle dysfunction during remission from recurrent back pain. McDonald D, Moseley GL, Hodges PW. Pain 2009; 142: 183-188.

The Myth of Core Stability. Lederman, Eyal. Journal of Bodywork & Movement Therapies. 2010; 14, 84-98.

Why do Some Patients Keep Hurting Their Back? Evidence of ongoing back muscle dysfunction during remission from recurrent back pain.  McDonald D, Moseley GL, Hodges PW. Pain 2009; 142: 183-188. Methods: This study evaluates the (t) control of short (deep) & long (superficial) fibers of t multifidi (MF) to determine if there is difference in 15 subjects (Ss) with a Hx of recurrent unilateral LBP but currently pain free at the time of the evaluation vs 19 healthy controls (ctls). Intramuscular electrodes were inserted in deep & superficial MF and surface electrodes were placed over t deltoids to record EMG activity during rapid arm flexion & extension to compare t onset of short & long MF fibers relative to t deltoids. T contraction of the MF w rapid arm flexion & extension is an unconscious feed forward activation of core stabilizers to provide active stabilization of the spine when motion of the upper extremity results in shifts of load and reactive torques in the spine. Results: 1. Deep MF fibers were active earlier than superficial fibers on both sides of t spine in healthy ctls & on t non-painful side in recurrent LBP Ss (feed-forward activation of unconscious stabilizing muscles), but were delayed on t previously painful side of t spine. 2. Activity of deep back MF muscles is different & delayed in Ss w recurrent unilateral LBP, despite resolution of Sx. 3. Changes in back muscles in Ss w a Hx of recurrent LBP are more profound in t deep fibers & on t side of Sx. These deep MF contribute up to 2/3 of t control of lumbar intersegmental motion. 4. Impaired control of these muscles is likely to compromise spinal function. 5. T persistence of these changes during remission implies persistent altered loading on spinal structures during remission, wh may be a cause of recurrent episodes. 6. Spinal injury specifically reduces t excitability of corticomotor inputs to t short fibers of t lumbar MF(L-MF). 7. An alternate motor strategy & subsequent changes in control of t deep MF can remain after an initial bout of LBP despite t resolution of Sx. 8. Such a change in strategy may indicate ongoing problems as alterations in control of back muscles lead to changes in joint loading & kinematics of t spine. 9. Resolution of BP doesn't imply a return to normal control of t deep back muscles. Studies demonstrate tt reduced CSA of deep back muscles remains in some Pts following an ALBP despite resolution of Sx.  Conclusion: This study presents evidence tt even though they are pain-free & between episodes of LBP, recurrent unilateral LBP Ss don't control their back muscles in t same way as healthy ctls. T findings raise t possibility tt this abnl pattern of muscle control, in t absence of pain, may leave t spine vulnerable to re-injury & predispose to recurrent episodes. Comments: This 2009 study's findings confirm the recent trends in motor control change research and does an excellent job in summarizing the conclusions based on the accumulation of this evidence over the past decade. Disturbances in motor control can be persistent and leave the area vulnerable to re-injury & recurrence. The findings suggest that the addition of exercise training to normalize & restore motor control patterns may have significant long-term benefits. In addition, the discussion about spinal injury specifically reducing t excitability of corticomotor inputs to t short fibers of t lumbar MF indicates the complexity of the reorganization of motor control changes with low back injury.
The Myth of Core Stability. Lederman, Eyal. Journal of Bodywork & Movement Therapies. 2010; 14, 84-98. This article reviews t literature over the past decade which describes the development and limitations of the Core Stabilization (CS) model for managing LBP. It notes that t passive human spine is an unstable structure. Stabilization is provided by t activity of the core trunk muscles. The transverse abdominis (TrA) has received much of t focus & is widely believed to be t main anterior component of trunk stabilization. However, current research indicates tt many different trunk muscles contribute to stability & their action may change according to varying tasks, movements & positions. The TrA contributes to stability, but this function is in synergy with every other muscle of t abdominal wall & beyond. The TrA acts in controlling pressure in t abdominal cavity for vocalisation, respiration, defecation, vomiting, etc. Patterns of muscle activation change moment-to-moment w different movements & postural tasks. To date, Lederman claims tt there are no studies tt show atrophy of abdominal muscles or tt strengthening abdominal muscles & TrA reduces back pain. This statement is controversial. A principle of CS is to teach Pts how to isolate t TrA from other abdominal muscles & from global muscles. However, with normal functional movements, motor recruitment & output are extensive and complex. To specifically train Pts to isolate & activate t TrA during functional movement, Pts have to override natural patterns of trunk muscle coactivation. Muscle-by-muscle activation does not exist. If you bring your hand to your mouth t nervous system ‘‘thinks’’ hand to mouth rather than flex biceps, then pectorals, etc. In CLBP we see a complex & broad reorganization of motor control in response to damage or pain. Lederman asserts tt there is no support from research that TrA can be singularly activated. So why focus on TrA or any other specific single muscle or muscle group? He concludes tt relative efficacy studies find tt when CS exercise focusing on t TrA are compared to general back exercise - both exercise approaches are demonstrated to be equally effective. Comments: This 2010 review article confirms the trend in the recent research tt focusing primarily on the TrA and abdominal hollowing is not the most effective strategy for providing dynamic core stabilization of the lumbar spine. Since 2007 a series of convincing studies have reported tt abdominal bracing (a trained coactivation of essentially all the core anterior, lateral and posterior stabilizers) provides better stabilization of the trunk than does abdominal hollowing. Furthermore, researchers report tt to have Pts focus exclusively on TrA control is at the cost of inhibiting other core stabilizing muscle such as the rectus abdominis, external obliques, and, to some degree, t internal obliques. These muscles are all involved in providing core stability, particularly during dynamic three-dimensional tasks. It is important that both internal and external obliques are active when there are torsional stress around the trunk. To train Pts to inhibit these muscles as they isolate and activate the TrA biomechanically makes no sense with dynamic activities and undermines the natural coactivation patterns of the body. Learning how to perform an "abdominal hollow" enhances the nervous system's awareness of the core and improves motor control, but it is better suited as an introductory training in static postures such as the four-point stance, sitting, standing, supine, and prone then it is when performing 3-dimensional dynamic activities. This also discusses possible limitations of abdominal bracing. It examines the complexity of motor reorganization with spinal injury & pain. There are changes in timing, endurance, force generation, coordination, ranges of motion, sequencing, and more.