Stress upon the lumbar spine during shovelling tasks

In the course of their investigations of formally recognized occupational disease (BK) 2108 (discogenic disorders of the lumbar spine), the accident insurance institutions assess the stress upon the lumbar spine caused by shovelling tasks. In the past, the results have differed widely owing to the lack of a uniform basis for assessment. Shovelling differs from other tasks such as lifting and carrying by the fact that the load is low in weight but is manipulated at some distance from the body by means of the shovel. In addition, shovelling always entails movements with extensive reach. This rules out the use of a two-dimensional analysis approach.

The objective of the present research project was to determine the stress upon the lumbar spine during shovelling tasks. Biomechanical motion and stress measurements were used to measure the external musculoskeletal stresses arising during shovelling activity upon five experienced, skilled test subjects from different areas of the construction sector. The measurements were performed in realistic work situations and under laboratory conditions. The study concept covered five different bulk products and three different work tasks in terms of the throw distance and height. The associated compression forces on the lowest lumbar intervertebral disk were calculated from the measured data by means of the "Dortmunder" biomechanical model.

The results of the study revealed a distinctly three-dimensional stress situation in the musculoskeletal system during shovelling activity. The shovelling techniques of the test subjects differed widely. They were divided into two groups, "standard case" and "exceptional case", the latter typical for piece work performed by composition floor layers, for instance. The maximum intervertebral disk compression forces varied accordingly, at mean values of approximately 3 ½ kN and 6 ¼ kN respectively. The corresponding duration of load exposure in the shovelling cycle was inversely proportional to the pace of work, falling from about 2 to 1 ½ s. No generic relationship was observed between the compression forces on the one hand and the bulk product type and throw distance and height on the other.

Based upon these data, experts from the BG BAU will now produce a uniform assessment pattern for estimation of the stress upon the lumbar spine during the various shovelling tasks.