Doctor of Philosophy (PhD)



Document Type



This dissertation contains three experiments all conducted in an outpatient physical therapy setting. Shoulder impingement is a common problem seen in overhead athletes and other individuals and associated changes in muscle activity, biomechanics, and movement patterns have been observed in this condition. Differentially diagnosing impingement and specifically addressing the underlying causes is a vital component of any rehabilitation program and can facilitate the individuals return to normal function and daily living. Current rehabilitation attempts to facilitate healing while promoting proper movement patterns through therapeutic exercise and understanding each shoulder muscles contribution is vitally important to treatment of individuals with shoulder impingement. This dissertation consisted of two studies designed to understand how active the lower trapezius muscle will be during common rehabilitation exercises and the effect lower trapezius fatigue will have on scapula dyskinesis. Study one consisted of two phases and examined muscle activity in healthy individuals and individuals diagnosed with shoulder impingement. Muscle activity was recorded using an electromyographic (EMG) machine during 7 commonly used rehabilitation exercises performed in 3 different postures. EMG activity of the lower trapezius was recorded and analyzed to determine which rehabilitation exercise elicited the highest muscle activity and if a change in posture caused a change in EMG activity. The second study took the exercise with the highest EMG activity of the lower trapezius (prone horizontal abduction at 130¢ª) and attempted to compare a fatiguing resistance protocol and a stretching protocol and see if fatigue would elicit scapula dyskinesis. In this study, individuals who underwent the fatiguing protocol exhibited scapula dyskinesis while the stretching group had no change in scapula motion. Also of note, both groups exhibited a decrease in force production due to the treatment. The scapula dyskinesis in the fatiguing group implies that lower trapezius function is vitally important to maintain proper scapula movement patterns and fatigue of this muscle can contribute and even cause scapula dyskinesis. This abnormal scapula motions can cause or increase the risk of injury in overhead throwing. This dissertation provides novel insight about EMG activation during specific therapeutic exercises and the importance of lower trap function to proper biomechanics of the scapula.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Landin, Dennis



Included in

Kinesiology Commons