Three-dimensional peak and cumulative shoulder loads and postures during non-occupational tasks: A preliminary investigation

Abstract

In order to obtain a complete understanding of the etiology of upper extremity musculoskeletal disorders, a spectrum of risk factors needs to be evaluated, within and external to the workplace. To date, cumulative shoulder loads (forces and moments) have only been documented during automotive assembly tasks. No information on shoulder loads during non-occupational tasks has been reported. To document 3D peak and cumulative shoulder loads and postures associated with non-occupational tasks. Seven male (35.8 ± 15.7 years) and six female (44.0 ± 14.3 years) healthy working-aged individuals volunteered for this study. A video-based 3D posture sampling approach was used to document shoulder joint postures while participants performed non-repetitive tasks in and around their own homes over a 2-hour period. A 3D rigid link segment model was used to calculate reaction forces and moments at the shoulder. Peak shoulder moments approached, and in some cases exceeded, published maximum isometric strength measurements, particularly in female participants. When extrapolated to a 7-hour shift, cumulative shoulder flexion and abduction moments, cumulative reaction caudal shear forces, and the time spent in non-neutral flexion and abduction were comparable in magnitude to those reported for light automotive assembly tasks. Non-occupational tasks should be evaluated more widely if a complete picture of the risk of musculoskeletal injury associated with shoulder loading is to be established. More work is needed to develop threshold limits for both peak and cumulative shoulder loads to improve injury prevention strategies.