Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Industrial and Managements Systems Engineering

Committee Chair

Ashish D Nimbarte

Committee Co-Chair

Majid Jaridi

Committee Member

Xiaopeng Ning


Shoulder musculoskeletal disorders (MSDs) put a huge burden on both employers and employees due to lost work days, healthcare costs and human suffering. Static and heavy industrial work, submaximal repetitive movement and arm elevation are frequently associated with shoulder MSDs. Previous studies indicated that factors such as force exertion levels, posture and hand gripping can influence the activation and fatigability of shoulder muscles. In this study, we explored the inter-muscle difference in shoulder activation during isometric/static force exertions. We suspected that shoulder muscles' attempt to stabilize the glenohumeral joint using the concavity compression mechanism may explain differences in the muscle activation pattern during shoulder exertions. Ten right-hand dominant male participants performed a 60 second static shoulder exertion using three force levels (10, 7.5 and 5 lbs.) in five directions (back, down, left, right and up). Results showed that muscle activity and fatigability were affected by force level and force exertion direction. Muscle exertion and fatigability were highly affected by 10lbs. force exertion. The findings of this study suggest that, during static shoulder exertion, pulling in up and right directions result in the highest muscle activity and fatigability.