Analysis of spinal and muscular activity during flexion/extension and free lifts.

Detailed measurements of the relative contributions of spine motion and pelvic motion during flexion-extension and free lifts (squat-type) are examined. The results are consistent with the conclusion that passive stretching of the ligamentous tissues transmits significant extensor moment in these activities, the power being supplied by the hip extensor complex acting on the pelvis. In addition, certain injuries result in measurable changes in the kinematic parameters that determine the ligamentous involvement, and these changes can be used to help evaluate spinal condition.