Three-dimensional motion analysis of lumbopelvic rhythm during trunk extension

Hip-spine coordination, known as the lumbopelvic rhythm, can be expressed as the lumbar-hip ratio. The lumbopelvic rhythm and lumbar-hip ratio can be used to assess lower limb function. We clarified the lumbopelvic rhythm and lumbar-hip ratio during trunk extension. We established a novel set of marker positions for three-dimensional motion analysis to assess the lumbar spinal angle. The original markers were placed on both paravertebral muscle groups at the 11th thoracic spinous process level, the 10th and 12th thoracic spinous processes, and the pelvis. We measured angle data during trunk extension using three-dimensional motion analysis, and the data for eight healthy male subjects were categorized into backward and forward phases. The lumbar-hip ratio increased significantly from 1.2 to 1.9 (mean, 1.6) in the backward phase, indicating considerable movement of the lumbar spine compared with hip movement in the latter phase. In the forward phase, the ratio decreased significantly from 1.9 to 0.5 (mean, 1.5). After completion of 80% of the forward phase, the lumbar-hip ratio decreased to