Effect of Grade III Lumbar Mobilization on Back Muscles in Chronic Low Back Pain: A Randomized Controlled Trial

Author Names
Mehyar, F., Santos, M., Wilson, S. E., Staggs, V. S., and Sharma, N. K.
Reviewer Name
Abby Bergeron, SPT
Reviewer Affiliation(s)
Duke University School of Medicine, Doctor of Physical Therapy Division

Paper Abstract
Background: Lumbar mobilization is a standard intervention for lower back pain (LBP). However, its effect on the activity of back muscles is not well known.
Objectives: To investigate the effects of lumbar mobilization on the activity/contraction of erector spinae (ES) and lumbar multifidus (LM) muscles in people with LBP.
Design: Randomized controlled study.
Methods: 21 subjects with LBP received either grade III central lumbar mobilization or placebo (light touch) intervention on lumbar segment level 4 (L4). Surface electromyography (EMG) signals of ES and ultrasound (US) images of LM were captured before and after the intervention. The contraction of LM was calculated from US images at L4 level. The normalized amplitude of EMG signals (nEMG) and activity onset of ES were calculated from the EMG signals at both L1 and L4 levels.
Results: Significant differences were found between the mobilization and placebo groups in LM contraction (p=0.03), nEMG of ES at L1 (p=0.01) and L4 (p=0.05), and activity onset of ES at L1 (p=0.02).
Conclusion: Lumbar mobilization decreased both the activity amplitude and the activity onset of ES in people with LBP. However, the significant difference in LM contraction was small and may not have clinical significance.

NIH Risk of Bias Tool
Quality Assessment of Controlled Intervention Studies
1. Was the study described as randomized, a randomized trial, a randomized clinical trial, or an RCT
-Yes
2. Was the method of randomization adequate (i.e., use of randomly generated assignment)?
-Yes
3. Was the treatment allocation concealed (so that assignments could not be predicted)?
-Cannot Determine, Not Reported, or Not Applicable
4. Were study participants and providers blinded to treatment group assignment?
-No
5. Were the people assessing the outcomes blinded to the participants’ group assignments?
-No
6. Were the groups similar at baseline on important characteristics that could affect outcomes (e.g., demographics, risk factors, co-morbid conditions)?
-Cannot Determine, Not Reported, or Not Applicable
7. Was the overall drop-out rate from the study at endpoint 20% or lower of the number allocated to treatment?
-Yes
8. Was the differential drop-out rate (between treatment groups) at endpoint 15 percentage points or lower?
-Yes
9. Was there high adherence to the intervention protocols for each treatment group?
-Yes
10. Were other interventions avoided or similar in the groups (e.g., similar background treatments)?
-Yes
11. Were outcomes assessed using valid and reliable measures, implemented consistently across all study participants?
-Yes
12. Did the authors report that the sample size was sufficiently large to be able to detect a difference in the main outcome between groups with at least 80% power?
-Cannot Determine, Not Reported, or Not Applicable
13. Were outcomes reported or subgroups analyzed prespecified (i.e., identified before analyses were conducted)?
-Yes
14. Were all randomized participants analyzed in the group to which they were originally assigned, i.e., did they use an intention-to-treat analysis?
-Cannot Determine, Not Reported, or Not Applicable

Key Finding #1
There was a significant difference between the mobilization and placebo groups in the changes of lumbar multifidus contraction, normalized amplitudes of EMG of erector spinae, and activity onset of erector spinae.
Key Finding #2
Mobilization led to reduced EMG activity of the erector spinae compared to the placebo group in participants with severe pain. Erector spinae EMG changes were not statistically significant in participants with moderate pain.
Key Finding #3
Mobilization led to increased lumbar multifidus contraction compared to the placebo group in only the participants with moderate pain.
Key Finding #4
The mobilization intervention significantly decreased the time of erector spinae onset compared to the placebo intervention.

Please provide your summary of the paper
As low back pain has been found to be associated with increased activity of erector spinae (superficial back muscle) and decreased activity of lumbar multifidus (deep back muscle), this 2020 randomized controlled trial aimed to examine how grade III lumbar mobilization impacts the activity of these muscles. Twenty-one participants with low back pain were randomly assigned to either the mobilization group (10 subjects) or the placebo group (11 subjects). The mobilization group received grade III central lumbar mobilizations at L4, while the placebo group received light touch to the same area. The intervention was delivered in four bouts of sixty seconds at two separate sessions (2 to 4 days apart). At each session, a normalization back-lift task and arm-lift task were performed by the subject and ultrasound, EMG, and pressure pain threshold measures were obtained to assess muscle activation and quantify pain. There was a statistically significant difference between the mobilization and placebo groups in the changes of lumbar multifidus contraction, EMG activity of erector spinae, and activity onset of erector spinae. However, the increases in lumbar multifidus contraction were only significant in subjects with moderate pain, and the change (3%) was lower than the reported minimum detectible change for this measure (11-13%). Further, the reduction in EMG activity of erector spinae was only significant in participants with severe pain. The participants in the mobilization group also demonstrated a significantly reduced time of erector spinae activity onset compared to the placebo group. The authors of this study concluded that this could indicate improved synergistic activity of the erector spinae and posterior deltoid during the prone arm-lift task.

Please provide your clinical interpretation of this paper. Include how this study may impact clinical practice and how the results can be implemented.

Abnormal activity of superficial and deep muscles in patients with low back pain may lead to increased pain and function limitations. Previous studies have examined how manual therapy interventions, such as thrust manipulation and lumbar mobilizations, can reduce pain and promote hypoalgesia. This study indicates that implementing grade III lumbar manipulations into the plan of care for such patients could normalize erector spinae and lumbar multifidus activation to better manage their chronic pain. Though the change in lumbar multifidus contraction may not be clinically significant, grade III mobilizations may still benefit patients by providing analgesic effects and decreasing erector spinae activity.