Core stability exercises in individuals with and without chronic nonspecific low back pain

Marshall PW, Desai I, Robbins DW. J Strength Cond Res. 2011 Dec;25(12):3404-11.

Quite simply, low-back pain (LBP) can be one of the most debilitating conditions that a patient has to experience, not to mention one of the most frustrating conditions to treat  as a clinician.  From early on in our training, we are taught to have our patients engage their core musculature throughout their rehabilitation exercises in an effort help alleviate the pain and/or prevent injury.  But what if what all we have been taught, and practiced, for years has been ineffective at best and deleterious at worst?  In this study Marshall et al. a examined the differences in muscle activation of the trunk in patients with and without LBP while performing common rehabilitation exercises under 2 conditions: with and without abdominal muscle bracing (defined as an active abdominal contraction where neither abdominal hollowing nor expansion were present).  They hypothesized that trunk muscle activity during selected rehabilitation exercises would be increased in individuals experiencing LBP, when compared to healthy controls, and that all subjects would see an increase in trunk muscle activation when performing abdominal bracing.  The authors also examined lumbar range of motion (LROM) in each subject while they performed each exercise.  The rectus abdominis (RA), external oblique (EO), and lumbar erector spinae (ES) were analyzed through surface electromyography with the data represented as percent maximum voluntary isometric contraction. Twenty subjects were recruited (LBP n=10; controls n=10) to perform 5 rehabilitation exercises: quadruped/bird-dog with alternating opposite arm/ leg raise, side bridge, modified push-up, squat to 70° of knee flexion, weighted shoulder flexion to 90° with a load representing 60% of their 1 rep max.  All subjects underwent 2 sessions timed one week apart.  Session 1 focused on abdominal brace training along with exercise familiarization; while session two focused on data collection.  In session 2, 3 single-repetition sets of each exercise were executed under both conditions (braced and unbraced).  After analysis, the authors were only able to partially support their primary hypothesis, compared to control patients muscle activity was higher in the RA and EO muscles for the side bridge but lower in the ES muscle for the quadruped exercises among patients with LBP.  The authors were able to support their second hypothesis in regards to abdominal bracing increasing muscle activation.  Muscle activation was greater for all exercises and in both groups during the braced condition compared to the non-braced condition.  In addition, during the braced condition each exercise selectively activated certain muscles more than others.  Lastly, there was no difference between groups, conditions, and exercises when examining LROM.

There are a handful of items to take into consideration clinically from the results of this study.  First off, this study had a very limited number of participants and to try to blanket our entire patient population with these results is not feasible nor is it encouraged.  One item that can be taken from this study and utilized is the fact that no patient experienced worsening of their LBP, which indicates that these exercises can be utilized safely for these individuals.  Another point that should be noted is that abdominal bracing did not have an effect on range of motion.  The authors state that utilizing abdominal bracing for LBP patients where spinal instability isn’t present might not be necessary.  They suggest that since bracing is associated with an increase in spinal compression, LBP patients that can perform the exercises with no pain may not need to perform the brace technique.  Coincidentally, the same might be able to be said for the healthy individual performing a low-back injury prevention program.  Perhaps they don’t need to perform the brace to still get the maximum result out of the intervention.  One area where abdominal bracing may have a positive influence is in patients with LBP due to muscular weakness.  This study focused on subjects with non-specific LBP, but some patients will present with weak core and hip musculature with a resultant pressure increase in the lumbar spine and ultimately pain. What are your thoughts on the use of abdominal bracing?  Are we using it too much in our everyday practice?

Written by:  Mark Rice
Reviewed by:  Stephen Thomas

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Marshall PW, Desai I, & Robbins DW (2011). Core stability exercises in individuals with and without chronic nonspecific low back pain. Journal of Strength and Conditioning Research, 25 (12), 3404-11 PMID: 22080309