Dynamic loads on the upper extremities during two different floor cleaning methods

Background. Biomechanical models have been used frequently to estimate the load on the low back and the lower extremities during occupational work tasks. The shoulder region has received much less attention although this area is a common site of work-related musculoskeletal disorders. Objective. The aim of the present study was to evaluate the mechanical loading of the upper extremities during floor cleaning performed with different techniques. Design. A comparative study of six subjects performing floor cleaning with two different techniques (mopping and scrubbing) in a laboratory setting. Methods. A “force handle” equipped with two force dynamometers was used for continuous measurement of three-dimensional forces on each hand, separately, during this two handed asymmetrical task. A link segment model of the upper extremities was used to calculate the mechanical loading of the elbows and shoulders. Electromyograms were recorded from six shoulder muscles. Results. Despite differences in movement patterns between mopping and scrubbing, only small differences were found in the moments of force. In accordance similar levels of electromyograms were found. Conclusion. In preventive strategies, changing the cleaning tool may not be sufficient to change the load on the shoulder muscles.