Since the launch of Nintendo's Wii Gaming Console in 2006, numerous cases related to musculoskeletal injuries known as "Wiiitis" (Wii ñ itis) have been reported in the literature or seen in the clinical practice. The minimal physical demands of playing Wii Sports may lead people to think it is just a game more than a physical activity and neglect the necessary warm-up or potential overuse that they would normally consider when playing actual sports. Anecdotally, there is a growing number of recreational tennis players who suffer from Wiiitis while playing Wii tennis, which requires minimal effort compared to playing actual tennis. With the increasing popularity of Wii as gaming or as rehabilitation tool, it is important for clinical scientists and professionals to understand the mechanism of Wiiitis and to find a preventative strategy to avoid injury. The purpose of this study is to compare the differences in strategies and biomechanical mechanisms when playing Wii tennis vs. regular tennis in 10 middle-age recreational tennis players and 10 age-matched non-players. This study will be an exploratory, between and within group comparative study. Upper extremity biomechanical characteristics such as shoulder and elbow joint angular velocity and torque, as well as the limb velocity and acceleration during flat (no topspin, no backspin) forehand swing, will be captured. Activation patterns of the posterior shoulder muscles during the swing will be simultaneously recorded using surface electromyography. The goal of this study is to identify the differences in shoulder biomechanics and muscle activation patterns in middle-age tennis players and non-players during a Wii tennis forehand swing, a regular racquet forehand swing with ball impact, and a Wii tennis forehand swing with a regular racquet. The ultimate goal is to understand the mechanism of injury so that a preventative strategy can be planned and implemented to avoid future injuries.