During various recreational/occupational daily activities, the sagittal curvature of the human lumbar spine (ie, lordosis) changes, influencing mechanics of the entire human spine. It affects the distribution of gravity/external loads among passive and active systems thus altering the load transmission in the structure. Due to the well-recognised role of lifting in industrial low-back injuries, the lumbar posture has attracted attention in a search for the safest lifting methods. Attempts to recommend optimal lifting techniques have not yielded satisfactory results due to many controversies surrounding the issue and lack of reliable models/measurements. Although the squat lift (whenever possible) is generally considered as a safer lift than the stoop lift in bringing the load closer to the body, the advantages in maintaining lordosis during lifting tasks, in general, is less understood. Such changes impose different external loads and internal strains/stresses in the lumbar spine tissues and as such influence the risk of injury and low-back pain. In a recent study, Cholewicki and McGill [1] observed that the experienced power lifters performed their lifts with relatively small lumbar flexion angles, much smaller than their respective maximum values during voluntary forward bending. The current study aims to investigate the detailed response of the entire lumbar spine (eg, tissue stresses) under large compression loads while the posture is altered, ie, the initial lordosis of ∼46° flattens by up to 38° (ie, flexion) or increases by up to 15° (ie, extension).

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