Low back pain (LBP) is one of the most common complaints amongst adults in the United States. It accounts for 2-3% of adult hospital visits¹. An estimated 70- 80% of U.S citizens will experience at least one instance of low back pain. over the course of their lives². 90-95% of people recover from a first a first instance. However, it is estimated that 60-75% of these will relapse. This study examines the etiology of this reoccurrence using two analysis methods:​ 1) segment rotations along with their ensemble average and rotational amplitude calculations and 2) Continuous Relative Phasing (CRP) and continuous relative phase variability (CRPvar). Previous studies have debated on the sensitivity of segment rotations to differentiate a population whose back pain has resolved from healthy controls and those who are currently experiencing back pain. Therefore, it is important to test the sensitivity of segment rotations. Given the similarity in our cohort of resolved and healthy controls, we hypothesized that segment rotations would be incapable of differentiating resolved LBP and healthy controls. This hypothesis was supported by the lack of significant group differences in rotational amplitudes, and the similarity of the ensemble average graphs.

More recent studies have proposed relative phasing methods that characterize the coordination segments as a method that may be more sensitive. Of these methods, CRP and its variability are one. The second hypothesis of this study was that CRP and CRPvar would find significant group differences in coordination patterns, coupled with decreased CRPvar. This hypothesis was largely supported by significant out-of-phase coordination patterns in lumbar-trunk and pelvic-lumbar flexion extension in our LBP group, and more in-phase coordination in pelviclumbar lateral bend. Decreases in CRPvar of pelvic-lumbar axial rotation and increases in pelvictrunk flexion extension and lumbar-trunk axial rotation were also observed. These latter results were unexpected.