Upper Limb Dynamic Mechanical and Anatomical Properties among Assembly Operators

Abstract

This study investigated upper limb mechanical and anatomical properties in assembly workers. Fourteen male assembly workers were recruited from selected jobs including power hand tool users and non-power hand tool users. Active dynamic mechanical properties of the upper extremity were measured using a free vibration apparatus. All workers underwent a physical examination, magnetic resonance imaging and completed a symptom survey. Employees were categorized as asymptomatic versus symptomatic based on reported forearm symptoms and physical exam findings. Symptomatic individuals had 46% less mechanical stiffness and a 59% less mass moment of inertia of the forearm than the asymptomatic group. Workers were stratified based on power tool use and two of the seven subjects who regularly used power nutrunners demonstrated MRIT₂ enhancement, which is indicative of muscle edema. T₂ MRI enhancement was not demonstrated in the seven subjects who did not regularly use power nutrunners.