History of Low Back Pain Affects Bend-and-Twist Coordination During a Repetitive Lift-Lower Task

Abstract

Motions which involve bending at the waist while twisting the trunk are occupational risk factors for low back pain (LBP). However, few studies have explored differences in lifting mechanics between individuals with and without a history of back pain (HBP); insight into these differences could elucidate adaptations due to LBP. PURPOSE: To compare the coordination between the trunk and the pelvis during a sustained asymmetric repetitive lifting task between a HBP group and a group with no history of LBP (NBP). METHODS: N=14 Soldiers (n=7 men/group) lifted a 11-kg box from ankle height in front to a shelf 45° off-center at waist height, and lowered it to the start position at 12 cycles/min for 10 min. Lifting side was alternated during the trial. Continuous Relative Phase (CRP) was used to calculate coordination between the pelvis sagittal motion and trunk rotation at the beginning (min1), middle (min5) and end of the bout (min9). 2-way ANOVA (Group X Time) were performed for CRP and CRP variability. Effect sizes (ES) were calculated as the mean difference relative to a pooled SD. RESULTS: There were no CRP differences between groups during the lifting phase. During the lowering phase, CRP was increased for HBP, and decreased for both groups toward the end of the bout (Fig 1). ES > 0.9 further indicated large practical differences. CONCLUSIONS: Differences between groups demonstrate residual consequences of LBP in an occupational scenario, even though the HBP group was pain-free for > 6 months prior to data collection. More in-phase coordination in the HBP group may represent a less adaptable coordination pattern compared to the NBP group, and may lend insight as to why these individuals are at increased risk for re-injury. Authors’ views, not U.S. Army or DoD.