Has the lumbar spine a margin of safety in forward bending?

Cadaveric lumbar motion segments (consisting of two vertebrae and the intervening disc and ligaments) were loaded to simulate forward bending movements in life, and the flexion angle at the elastic limit was measured. These flexion angles were then compared with flexion angles obtained from X-rays of healthy volunteers in the erect standing and fully flexed positions. The comparison showed that, when people adopt the static, fully flexed posture, the osteoligamentous lumbar spine is flexed about 10° short of its elastic limit.