Spinal Manipulation Increases Trunk Muscle Activity
Spinal Manipulation Increases Trunk Muscle Activity
The role of muscles in stabilizing the spine has drawn increasing attention in recent years. People with low back pain (LBP) may use a different motion pattern and motor control strategy in the spine compared to normal subjects, which may be due to pain or damage to tissues. To document the function of muscles in the back, electromyography (EMG) may be used. EMG measures muscle action and force, and it has been closely associated with muscle strength. However, few studies have investigated the effect of spinal manipulative therapy (SMT) on the EMG output of the trunk muscles.
In a recent clinical study, it was noted that patients receiving SMT via an Activator instrument, had increased post-SMT EMG output. Compared to the pre-SMT EMG readings of maximum voluntary contraction of the spinal extensors, the post-SMT readings were much higher. This unexpected finding prompted the current paper by the same author.
Three groups of subjects participated in this study. The SMT group was assessed and adjusted using the Activator. The adjustment was followed by a test for dynamic stiffness and algometry. Before and after SMT, patients were asked to perform a prone contraction trunk extension while surface EMG electrodes monitored erector spinae muscle activity. The second group was given a sham SMT, and dynamic stiffness and algometry assessment. A control group received none of the treatments or assessments other than the EMG.
Results: Patients in the SMT group demonstrated a significant increase in post-SMT erector spinae EMG output; the sham and control groups did not. These findings indicate that altered muscle function may be a potential short-term therapeutic effect of mechanical force, manually assisted adjusting, and they form a basis for a randomized controlled clinical trial to further investigative acute and long-term changes in low back function.
Keller T, Colloca C. Mechanical force spinal manipulation increases trunk muscle strength assessed by electromyography: A clinical trial. Journal of Manipulative and Physiological Therapeutics 2000:23, pp. 585-595.
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