The effect of personality type on muscle coactivation during elbow flexion

A great deal of interest has been generated recently regarding the influence that psychosocial factors may have on the reporting of and disability associated with work-related musculoskeletal disorders. The current study considers the potential influence of one psychosocial factor--personality type--on basic neuromuscular control strategies and biomechanical loading. The study investigated the hypothesis that Type A people exhibit increased muscular antagonism relative to their Type B counterparts. Volunteers participated in an EMG-based biomechanical study to investigate the coactivation patterns of the major muscles that span the elbow joint during elbow flexion exertions. Results showed that, averaging across all conditions, the antagonist muscle activity was significantly higher for Type A individuals than for their Type B counterparts (10% of maximum for Type A, 5.5% of maximum for Type B). Although the study was somewhat limited in its size and scope, the results indicate that certain psychosocial factors may be more than a filter in postinjury response and may directly influence biomechanical loading. A potential application of this research is an increased awareness that certain individuals may be at greater risk of developing work-related musculoskeletal disorders.