ABSTRACT
Work tasks which require high force levels may be improved by changes which reduce the exposure level; however, an evaluation of such interventions requires more detailed biomechanical analyses. For example, the forces required when using two specific floor cleaning tools, a mop and a scrub, have been compared (Søgaard et al., 1998). Hand force registrations and video recordings were used to describe three-dimensional external forces and movements (Figure 11.3). By applying inverse dynamics and a 3-D linked-segment model glenohumeral torques were calculated. The highest mean moments of force were registered in shoulder flexion and they were similar for mopping and scrubbing (11 per cent and 11 per cent MVC, respectively for one shoulder, 13 per cent and 9 per cent MVC for the other shoulder). However, bilateral EMG measurements on m. deltoideus, m. trapezius and m. infraspinatus showed higher peak EMG levels on m. deltoideus of one shoulder and on m. infraspinatus of the other shoulder during scrubbing as compared to mopping. Inspite of this the authors concluded that the exposure level could not be sufficiently changed by changing the cleaning method because similar peak EMG levels from four muscles, similar static EMG levels on all six muscles and similar moments of force were recorded.
