The objective of this study was to determine if  mechanical force, manually-assisted (MFMA) spinal manipulative therapy  (SMT) affects paraspinal muscle strength assessed using surface  electromyography (sEMG).

Summary of Background Data:

A disorder in the  neuromusculoskeletal system may result in excessive load sharing of the  passive system that can cause abnormal motion and increased deformation  of its highly innervated structures resulting in LBP. SMT has been found  associated with reflex responses in the back musculature, however the  clinical relevance of such findings are not understood. The role of  rehabilitation programs of improving objective outcomes including  increases in trunk muscle strength are important goals of patient care.


This study is a prospective controlled clinical trial  comparing sEMG output in an active treatment group and two control  groups.


Twenty consecutive LBP patients (SMT treatment group)  performed maximum voluntary contraction (MVC) isometric trunk extensions  while lying prone on a treatment table. Surface, linear enveloped sEMG  was recorded from the erector spinae musculature at L3 and L5 during the  trunk extension procedure. Subjects were then assessed using the  Activator Methods Chiropractic Technique (AMCT) protocol, during which  time they were treated using MFMA SMT. The MFMA SMT treatment was  followed by a dynamic stiffness and algometry assessment, after which a  second or post MVC isometric trunk extension and sEMG assessment was  performed. Another twenty subjects were randomized into two control  groups, a sham-SMT group, and a control group. The sham-SMT group  underwent the same experimental protocol with the exception that the  subjects received a sham-MFMA SMT and dynamic stiffness assessment. The  control group received no SMT treatment, stiffness assessment, or  algometry assessment intervention. Within group (pre-SMT vs. post-SMT  sEMG output) and across group analysis of sEMG output from MVC (pre/post  sEMG ratio) was performed using a paired observations t-test (POTT) and  analysis of variance (ANOVA), respectively.


Outpatient chiropractic clinic, Phoenix, AZ, USA. Subjects: Forty total subjects participated in the study.  Twenty LBP patients (9 females and 11 males, 35 years and 51 years,  respectively) and twenty age and gender matched sham-SMT/control LBP  patients (10 females and 10 males, 40 years and 52 years, respectively)  were assessed.

Main Outcome Measures:

Surface electromyographic recordings  during isometric maximum voluntary contraction trunk extension were used  as the primary outcome measure.


Nineteen of the 20 patients in the SMT  treatment group showed a positive increase in sEMG output during MVC  (range -9.7% to 66.8%) following the active MFMA SMT treatment and  stiffness assessment. The SMT treatment group showed a significant  (POTT, P<<0.001) increase in erector spinae muscle sEMG output  (21% increase compared to pre-SMT levels) during MVC isometric trunk  extension trials. There were no significant changes in pre vs. post- SMT  MVC sEMG output for the sham-SMT (5.8% increase) or control (3.9%  increase) groups.

Reference: Tony S. Keller, Ph.D. and Christopher J.  Colloca, D.C.; Mechanical Force Spinal Manipulation Increases Trunk  Muscle Strength Assessed By Electromyography: A Comparative Controlled  Clinical Trial; Proceeding of the 27th Annual Meeting of the International Society for the Study of the Lumbar Spine, Adelaide, Australia, April 9-13, 2000.