The flexion-relaxation (FL/R) phenomenon was first reported in 1948 by Allen. It was noted in normal pain free subjects that during forward flexion of the trunk, there was an abrupt silence of the electrical signal from the lumbar paraspinal muscles near the end of motion. FL/R has since become a recognized indicator for low back dysfunction.
Recently, Meyer et.al. have noted the presence of FL/R in the cervical spine using dynamic EMG studies. It was the purpose of this study to determine whether Cervical FL/R could be measured using hand-held integrated SEMG apparatus at the static end-range of motion in normal subjects.
A Precision 960 SEM G unit (Precision Diagnostic Technology, Inc., 80-200 Hz. bandwidth) was used for collection of EM G data at bilateral paras pinal sites in the cervical spine, at the levels of C2, CS, C7 and Tl with the subjects in the neutral sitting position, and with the subject's neck fully flexed.
The difference between the flexed and neutral data was found to be significant for the C2 level only (p < 0.01). Using the criterion that FL/R is present if the flexed EMG value is less than the neutral EMG, then FL/R was found in 15/23 cases. Applying a second criterion for the presence of FL/R, i.e. that FL/R is present whenever the EMG in the flexed position falls below 2 microvolts, then FL/R was found in 20 out of 23 subjects.
Author Keywords: Cervical Spine, Electromyography, Chiropractic
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