Evaluation and assessment of lumbar load during total shifts for occupational manual materials handling jobs within the Dortmund Lumbar Load Study -: DOLLY

The load on the lumbar spine during occupational manual materials handling was previously investigated with respect to short activity sections or to specified load-handling types such as lifting or carrying. Within the so-called Dortmund Lumbar Load Study, analysis of the occupationally induced load on the lumbar spine during total working shifts in the field of surface construction, drop forge, industrial meat processing, and refuse collection was performed on the shop-floor. The body postures adopted, the action forces applied at the hands, and the resultant lumbar load for all load-handling tasks were analysed for 2 shifts in each field on the basis of video evaluations. Via a newly developed detailed classification procedure, the spatial position of the body segments as well as amplitude and direction of the action forces were described in a detailed manner. Consecutive biomechanical model calculations lead, for total shifts, to time courses of various measures for the load on the lumbar spine, such as flexion or torsional moments of force as well as compression and shear forces at the lumbosacral disc. In relation to recommended limits for the maximal disc compression provided in the literature, lumbar load is exceeded in numerous situations during a shift, in particular, with regard to persons of higher age. In a dose model applied in this study, the cumulative effect of single-task exposures was considered by superproportional weighting of the compressive force with respect to the corresponding duration of a working task.