Influence of dynamic factors and external loads on the moment at the lumbar spine in lifting.

Flexion-extension moments occurring at the L5-S1 level of the spine were calculated when subjects lifted a box weighing from 50 to 250 N. Lifting was performed at normal and fast speed, and the lifts were performed using a freestyle and a leglifting technique. The peak moment increased linearly with increasing load. The moment/load relationship was significantly influenced by lifting speed, and a higher moment occurred at each load level when lifting fast. Lifting speed was reduced when the external load was increased, particularly when the load was 150 N and higher. Moments when lifting using the leglifting technique were lower than when lifting freestyle.