Novice lifters exhibit a more kyphotic lifting posture than experienced lifters in straight-leg lifting

摘要

As torso flexion and repetitive lifting are known risk factors for low back pain and injury, it is important to investigate lifting techniques that might reduce injury during repetitive lifting. By normalizing lumbar posture to a subject's range of motion (ROM), as a function of torso flexion, this research examined when subjects approached their range of motion limits during dynamic lifting tasks. For this study, it was hypothesized that experienced lifters would maintain a more neutral lumbar angle relative to their range of motion, while novice lifters would approach the limits of their lumbar ROM during the extension phase of a straight-leg lift. The results show a statistically significant difference in lifting patterns for these two groups supporting this hypothesis. The novice group maintained a much more kyphotic lumbar angle for both the flexion (74% of the lumbar angle ROM) and extension phases (86% of the lumbar angle ROM) of the lifting cycle, while the experienced group retained a more neutral curvature throughout the entire lifting cycle (37% of lumbar angle ROM in flexion and 48% of lumbar angle ROM in extension). By approaching the limits of their range of motion, the novice lifters could be at greater risk of injury by placing greater loads on the supporting soft tissues of the spine. Future research should examine whether training subjects to assume more neutral postures during lifting could indeed lower injury risks. Torso flexion and repetitive lifting are known risk factors for low back pain and low back injuries (Bernard, 1997; Hoogendoorn et al, 1999; Marras and Granata, 1995). Punnett et al. (1991) examined the trunk postures of automobile assembly workers and found low back disorders to be associated with tasks involving both severe and mild torso flexion. The risk of low back disorders also increased with duration. Since torso flexion and repetitive lifting cannot be completely removed, it is important to investigate what lifting techniques might reduce injury during repetitive lifting. Coordination of the lumbar spine with trunk, pelvis, and whole body motions has been of particular interest to the physical therapy and rehabilitation community.