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).
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.
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.