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Quantification of t he lumbar spine compression and shear forc es is a con tinuing ch allenge in b iomechanics. The purpose of this study is to develop a virtual model with the ability to determine the kinetics of lu mbar spine joints during complex activities.

BACKGROUND: In industrial supply companies, the pressure for productivity can conflict with the ergonomic safety of material handling on the loading dock, with workers tending to rush through the lifting tasks at the expense of higher biomechanical loads. OBJECTIVE: The purpose of this investigation was to determine: a) the potential benefit of introducing an ergonomic safety initiative, which slows the speed of lifting, and b) the need to use more complex biomechanical models in work assessments. PARTICIPANTS: One experienced worker and nine university male students between the ages of 22 and 42 participated in this study; all reported no recent history of musculoskeletal injuries. METHODS: The investigation involved stacking empty propane cylinders, one on top of the other, while using a single-handed lift at a self-selected slow and fast pace, and lifting small, weighted beverage bottles at a slow, medium and fast pace, this time using a metronome to set the pace. RESULTS:The results demonstrated a significant main effect for lift pace for both peak static and dynamic external moments at the shoulder and at L4/L5, with a larger effect occurring with the lighter loads. A reduction in peak acceleration with heavier weights partially explained the confounding influence from load. Significant differences occurred between the peak static moments according to load, suggesting an accommodation in the lift strategy. There were also significant differences between the static and dynamic external moments, which became meaningful when the lift pace was medium or fast, suggesting that a dynamic analysis is not necessary if the pace is slow. CONCLUSION: This investigation further supports that the pace of lifting is an important work factor in safe lifting and material handling.