Shoulder Muscle Oxygenation during Repetitive Tasks

Abstract

The purpose of this study was to quantify shoulder muscle oxygenation during repetitive shoulder exertions that were similar to motions found in automobile assembly tasks. Ten subjects participated in the study. There were three independent variables: 1) shoulder flexion angle; 2) frequency; and 3) force. The dependent measure was percentage change in muscle oxygenation for the anterior deltoid and trapezius. The results showed significant muscle oxygenation decreases for each of the main effects (shoulder flexion angle, frequency and force). The interaction of force and repetition was significant for the anterior deltoid, indicating that, as repetition increased the magnitude of the differences between the force levels increased. The interaction of repetition and shoulder angle was also significant. The results of this research illustrate that ergonomists need to consider the interaction of injury risk factors that may trigger musculoskeletal disorders of the shoulder.