The catcher is actively involved, defensively, in every pitch that is thrown during the duration of a baseball or softball game. Because catchers play such an active role, the outcome of the game can be decided on their ability to keep base runners from stealing and advancing into scoring position. The ability to throw out a stealing runner is a necessary skill that catchers must possess in order to be successful at their position. To keep a base runner from stealing catchers have the option of throwing down to second base from either their stance or their knees. Despite the importance of the catcher’s role, baseball and softball literature lacks quantitative data describing their throwing motion. Without proper knowledge of the catcher’s throwing motion it is impossible to identify detrimental pathomechanics that may be present. Improper mechanics that are performed repetitively may lead to injury and shorten the catcher’s career.

In addition to identifying the kinematics of the throwing motion of catchers it is also necessary to understand the muscle activations associated with those kinematics. Muscle activity reflects the muscle effort for initiating movement of the joints. The muscles analyzed were bilaterally gluteus maximus and medius, throwing arm biceps, triceps, deltoid, and scapular stabilizers. These muscles have previous been identified as active during the progression of throwing. Therefore the purpose of this study was to quantitatively describe and compare the kinematics and muscle activations of catchers throwing down to second base from their stance and their knees.