INTRODUCTION

The issue being addressed in this study concerns a rotator cuff injury, and the effects on physical activity. Specifically, "Does the non-injured shoulder generate more power than the injured shoulder?" Any determined variances in power may be an indication that an injury to the rotator cuff can lead to weakness/instability of the shoulder. It has been previously reported that injury to the rotator cuff can impair athletes from performing many overhead movements, especially in sports requiring an individual to throw an object (Weinstabl et al., 1996). However, the team is concerned with how this type of injury may hinder everyday activities such as simple lifting movements.

Our purpose is to examine any significant differences in the power generated by an individual with a pre-existing shoulder injury in comparison to an individual with a normal/healthy shoulder. To do so, we will examine the motions of two subjects performing a seated overhead military press. One of the subjects has a pre-existing injury to the rotator cuff, while the other has a normal/healthy rotator cuff. The idea is to have the subjects exert a sub-maximal effort in order to move an equal amount of weight. Since power is determined by force and velocity (P=FV), the differences in power will be determined by the subject's velocity during the press. The reason being is that the force (or weight of the press) should be the same for both subjects, therefore, power will only differ based on the relative velocity of each subject's movements. We predict that the injured subject will have a slower velocity during the movement, and therefore produce less power than the non-injured subject. We also suspect that any resulting differences in power may be attributed to a lack of strength and/or instability caused by the rotator cuff injury.