Swinging a baseball bat effectively in a game requires generating speed very quickly to impart force to the oncoming ball. The ball itself imparts force on the player. The combination of the two forces along with either specific weak muscles or improper technique can lead to chronic injuries in the shoulder for baseball players.
The batting stance is the first component of a batter's swing, serving as the ready position for the pitch. Some batters hold their hands higher than shoulder level while others keep their hands more relaxed around chest level. As the pitch is delivered, the batter makes what is called a timing step that begins the rotation of the hips, front knee and front shoulder, as the back hand pulls the bat backward to generate torque prior to launching the bat forward at the ball.
The humerus and the scapula are the two primary bones of the shoulder. The shoulder is designed to rotate the arm in a circular fashion as a ball and socket joint. Major muscles affecting shoulder function include the biceps, tricpes, trapezius and deltoid. Many smaller muscles are responsible for fine motor function, including four muscles that cross and connect the scapula to the humerus, creating the rotator cuff.
Because the shoulder has many muscles, ligaments and tendons, there are many opportunities for injury. Prolonged pain in the shoulder suggests that a proper diagnosis is required. Acute injuries can occur as a player attempts to generate bat speed with muscles not warmed up properly. It is more likely that a player will develop chronic injury from repetitive improper hitting. A knot in the trapezius muscle had Cincinnati Reds third baseman Scott Rolen sidelined early in 2011. The deltoid and biceps tendons are other areas of possible chronic pain and knots resulting from the initial force generated in the swing.
Many chronic use injuries follow the same rehabilitation protocol. Rest to reduce swelling and promotes healing. Ice the shoulder after playing. Warm up and stretch before play to prepare the shoulder properly for swinging. Stretching will release knots by lengthening muscles but shouldn't be done past the point of pain. However, these modalities will provide only temporary relief if an underlying issue exists. Weak muscles must be strengthened and proper form used. Players keeping their hands higher up in the stance will create less strain by dropping their hands a bit lower.