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Activator Methods International Ltd.
2950 N. Seventh Street, Suite 200
Phoenix, AZ 85014
ofc 602-224-0220
fax 602-224-0230
toll free 1-800-598-0224
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Subject: Neurophysiological Research
Title: Electromyographic Responses To Mechanical Force, Manually Assisted Spinal Manipulative Therapy
Reference: Colloca CJ, Keller TS. Electromyographic reflex responses to mechanical force, manually assisted spinal manipulative therapy. Spine 2001a; 26(10): 1117-24
ABSTRACT
Study Design: Surface electromyographic reflex responses associated with mechanical force, manually-assisted (MFMA) spinal manipulative therapy (SMT) were analyzed in this prospective clinical investigation of 20 consecutive patients with low back pain.
Objectives: To determine the electromyographic reflex responses in human paraspinal muscles during high loading rate MFMA SMT of the thoracolumbar spine and sacroiliac joints.
Summary of Background Data: Spinal manipulative therapy has been investigated for its effectiveness in the treatment of patients with low back pain, but its physiologic mechanisms are not well understood. Noteworthy is the fact that SMT has been demonstrated to produce consistent reflex responses in the back musculature; however no study has examined the extent of reflex responses in patients with low back pain.
Methods: Twenty patients (10 male & 10 female, mean age of 43.0 years) underwent standard physical examination upon presentation to an outpatient chiropractic clinic. Following repeated isometric extension strength tests, short duration (< 5 msec), localized PA manipulative thrusts were delivered to the sacroiliac (SI) joints, and L5, L4, L2, T12, T8 spinous processes (SPs) and transverse processes (TPs). Surface, linear enveloped, electromyographic (sEMG) recordings were obtained from electrodes located bilaterally over the LS and L3 paraspinal musculature. Force-time and sEMG-time histories were recorded simultaneously in order to quantify the relationship between SMT mechanical and electromyographic response. 1600 sEMG recordings were analyzed from 20 SMT treatments and comparisons were made between segmental level, segmental contact point (spinous vs. transverse processes), and magnitude of the sEMG reflex response (peak-peak (ratio and relative mean sEMG). Positive sEMG responses were defined as >2.5 p-p baseline sEMG output (> 10% isometric extension sEMG output). SEMG threshold was further assessed for correlation for patient self-reported pain and disability.
Results: Consistent, but relatively localized sEMG reflex responses occurred in response to the localized, brief duration MFMA SMT thrusts delivered to the thoracolumbar spine and SI joints, The tune to peak tension (sEMG magnitude) ranged from 50-200 msec and the reflex response times ranged from 2-4 msec, the latter consistent with intra-spinal conduction times. Overall, the 20 treatments produced systematic and significantly different L5 and L3 sEMG responses, particularly for thrusts delivered to the lumbosacral spine. Thrusts applied over the TPs produced more positive sEMG responses (25.4% response for 20 thrusts) in comparison to thrusts applied over the SPs (20.6%). Moreover, left side thrusts and right side thrusts over the TPs elicited positive contra-lateral L5 and L3 sEMG responses, When the data was examined across both treatment level and electrode site (L5 or L3, L or R), up to 95% of patients showed a positive sEMG response to MFMA SMT. Patients with frequent to chronic LBP symptoms tended to have a more marked sEMG response in comparison to patients with occasional to intermittent LBP.
27th Annual Meeting of the international Society for the Study of the Lumbar Spine, Adelaide, Australia, April 9-13, 2000.
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