Dynamic Shoulder Loads in Reaching and Materials Handling Tasks

Abstract

This presentation describes the dynamic shoulder moments and peak strength requirements resulting from the performance of typical arm reach and materials handling tasks. It is shown by a dynamic biomechanical analysis that normal right arm reaches to the glove box or passenger door in a vehicle will cause peak moment loads sufficient to exceed the expected strengths of some drivers, particularly women. Using a similar biomechanical analysis of lifting and lowering 10 Kg and 20 Kg loads (both manually and with mechanical assistive devices) the peak strength requirements on both shoulders would exceed about one-third of women's capabilities (particularly when attempting to move the load with a large articulated balance arm device). It is concluded that such tasks are quite stressful to the shoulder musculoskeletal system, and should be given greater attention in job and vehicle ergonomic studies and modeling activities.