J Manipulative Physiol Ther. 1989 Dec; 12(6): 419-27.

Effect of unilateral spinal adjustments on goniometrically-assessed cervical lateral-flexion end-range asymmetries in otherwise asymptomatic subjects.

Nansel DD, Cremata E, Carlson J, Szlazak M.

Department of Physiology and Pathology, Life Chiropractic College-West, San Lorenzo, CA 94580.

A triple blinded, multiple-measure, experimental protocol was employed in order to investigate the effectiveness of unilateral cervical adjustments on goniometrically assessed cervical lateral-flexion asymmetries. On pretest, subjects selected for the experiments exhibited mean left-right lateral-flexion differences of approximately 14 degrees. In subjects which either received no intervention, or had been subjected only to preliminary palpatory and set-up procedures but no thrust, asymmetry magnitudes were found to be unchanged on goniometric posttesting done 30-45 min later. However, in subjects which received lower cervical adjustments performed on the side of most restricted end-range, there was a dramatic reduction in asymmetry magnitudes. Furthermore, the adjustment procedure used in this investigation appeared to be relatively side-specific, since adjustments, when delivered to the less restricted side, were only marginally effective in ameliorating the asymmetries. Potential clinical relevance as well as the possible structural or physiological mechanisms responsible for the results obtained in the study are discussed.