A method to determine joint moments and force distributions in the shoulders during ceiling work — a study on house painters

Objective. The purpose of this study was to propose and apply a method to study the net load and the force distribution in the shoulder during sanding of a ceiling. Design. Sanding of a ceiling was studied in an experimental set-up. Background. Among painters there is a high frequency of neck and shoulder complaints and some particularly strenuous tasks are sanding and painting of ceilings with tools attached to extension handles. Methods. A biomechanical model predicted the load pattern in the shoulder from measured external forces and body postures. Measurements were made on 40 subjects by means of a force plate, an extension handle supplied with two pairs of strain gauges and a load cell, and a 3D optoelectronic measurement system. Results. Work techniques may seem to be similar at visual inspection, but nevertheless produce quite different loading patterns in the shoulder. The observed work techniques varied largely among the subjects but the intra-individual variability was rather small. Conclusions. The study showed that the proposed method can be used to evaluate loads and force distribution in the shoulder. Since the method involves the use of a biomechanical model that can scarcely be validated, results must be interpreted cautiously.