An electromyographic analysis of the elbow in pitching.

Elbow injuries are common in baseball pitchers. Curve balls are thought to increase this risk, particularly if the athlete begins throwing this pitch at an early age. The purpose of this paper is to identify forearm muscle firing patterns during the pitching cycle in an effort to understand this etiology. Dynamic EMG was performed on eight collegiate pitchers to evaluate extensor digitorum communis, brachioradialis, flexor carpi radialis, flexor digitorum superficialis, extensor carpi radialis longus, extensor carpi radialis brevis, pronator teres, and supinator. Each subject threw a fast ball and curve ball, which were filmed at 450 frames per second and synchronized with the EMG. These signals were converted from analog to digital records. Results showed low to moderate activity in all muscles during all phases of the pitch. The function is probably positioning to accept the transfer of energy from the larger trunk and girdle structures. The most notable difference between the fast ball and curve ball is a slight increase in the extensor carpi radialis longus and extensor carpi radialis brevis activity during late cocking, acceleration, and follow-through of the curve ball as compared to the fast ball. This difference, however, is not significant. In addition, there was no significant difference between the fast ball and the curve ball in the flexor-pronator group in any phase. We cannot substantiate that medial elbow problems are a result of an increase in the use of flexor muscles during the curve ball pitch.