The Application of Surface Electromyography for Subluxation Detection

Edward Owens, MS, DC
Andrew Ashton
Jeong Pil Park
Heenam Park

ABSTRACT

The use of surface electromyography (sEMG) in chiropractic is a matter of some controversy. One the one hand, there are commercial systems available for purchase for clinical use by practitioners, and, on the other, there are more costly research-grade systems in use in the colleges for study of muscle function associated with low back pain.

There have been both critical and supportive articles in the literature over the past 5 years, but no consensus has been reached. Some of the issues of contention are technical: the use of hand-held versus attached electrodes, the use of contact gels, the position in which to perform scans and how to account for the effects of electrode contact or skin thickness on the amplitude of the sEMG output. While there have been reliability studies performed with some systems, neither of the available commercial scanning systems have published studies on the reliability of their protocols.

Other issues revolve around interpretation of sEMG findings: Are asymmetries of amplitude important clinical measures? Is asymmetry a sign of dysfunction? While there have been several studies of the validity of laboratory style sEMG to detect the muscle dysfunction associated with low back pain, the sensitivity and specificity of scanning sEMG in detecting subluxation are unknown. It is generally assumed that any asymmetry is of clinical import, but this assumption has not been tested.

A project is underway to help bridge the gap between the two different styles of sEMG. A protocol has been developed to test some of the assumptions of scanning sEMG, but using the more rigorous techniques of laboratory methods. The protocol involves measuring integrated EMG bilaterally from two paraspinal levels using attached electrodes and a digital lab amplifier (BioPac). Sitting relaxed and sitting erect postures will be assessed, along with the effects of standardized postures and spinal loads. These standardized postures and loads will enable the use of normalization procedures to account for electrode contact and skin resistance differences.

Data is currently being collected on student volunteers. Results will be presented at the 2003 Verterbal Subluxation Research Conference.