The manual handling of loads may cause high loads on the spine, which can be regarded as a reason for the occurrence of disc disease. Despite progressive use of handling aids still many manual activities are executed. This applies, in particular, to the transportation of loads with a wheelbarrow and to shovelling loose materials. For these activities the forces and, above all, also their dynamic parts transferred to the body, are unknown to begin with, so that they must be registered by measuring techniques.

For studying these activities a special force measuring device were developed and built into the particular equipment. These measuring techniques enabled the registration of action forces exerted by the user according to size and direction. With knowledge of the performed action forces and of the occurring body posture, characteristic values of the load on the lumbar spine was determined with the help of the biomechanical model The Dortmunder (Jäger and Luttmann, Med. Orthop. Tech., 1992), e.g. the compressive force on the L5-S1 disc is calculated for different activities.

The results of the studies for load transportation with the wheelbarrow show that the compressive force is substantially higher while raising and lowering than while pushing. Driving over uneven ground also causes an increased compressive force. In the time course for compressive force step-synchronous fluctuations show up, the height of which depends on the execution speed, on the load weight and on the ground passed over. In the case of the task "shovelling of loose materials" pronounced load peaks occurred in the time courses for compressive force. The high lumbar load results from a strongly asymmetrical body posture in connection with likewise strongly asymmetrically action forces.

The results show that when shovelling in particular high loads occur on the lumbar spine. Thus earlier physiological investigations are supplemented also regarding the load on the skeleton, according to which shovelling represents one of the "heaviest of all possible work forms" on account of its high energetic loads (Rohmert, Praktische Arbeitsphysiologie, Thieme Verlag, Stuttgart 1983).

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