Influence of dynamic factors on the lumbar spine moment in lifting

Flexion-extension moments occurring at the L5-S1 level of the spine were calculated when subjects lifted a 150N box at slow, normal and fast speeds. Three methods of lifting were used: leg-lifting, back-lifting and free-style lifting. The peak moment increased linearly with increasing lifting speed. The increase was greatest for back lifts, but occurred with the other two lifting techniques as well. Inertial forces should be considered when analysing lifting tasks biomechanically. Excessive speed of lifting, including jerking, should be avoided.