All throwing and many hitting and catching skills require some rotation of the arms. The rotation usually takes place in the shoulder, elbow and wrist joints although it can be isolated to one or two joints depending upon the type of throw or hit. For example, in baseball fielding when reaching out to the side to catch a ball the arm rotates to correctly position the glove hand.
In ball catching it is usually necessary to rotate the arm (or forearm) to correctly position the hand. In boxing when throwing a jab there is usually medial rotation of the arm. In volleyball spiking, you laterally rotate the arm in the shoulder in the preparatory movements and then medially rotate prior to the hit and in the follow through. Thus specificity of rotator cuff exercises is very important for injury prevention and enhancing performance.
In throwing, as for example in baseball pitching, there is pronation of the hand and medial rotation in the shoulder joint when throwing a fastball and different breaking balls. Thus there is a great deal of arm rotation which involves the rotator cuff and other muscles surrounding the shoulder joint in addition to the forearm and wrist joints and muscles.
To strengthen these muscles to assist in executing the different movements with the arms in different positions, and to help prevent rotator cuff injuries you should do medial and lateral rotations with the Strength Bar. These exercises are preferred over the typical medial and lateral rotation exercises in which a bent arm is held against the body while the athlete executes internal and external rotation. They exemplify specificity of rotator cuff exercises.
These traditional exercises (medial and lateral rotation with the elbow alongside the body)are good for general conditioning but they do not strengthen the muscles in a specific manner, i.e., as they are used in the various throwing, hitting and catching actions. When you do medial and lateral rotation with the Strength Bar you can more closely duplicate the positions and actions seen in the sport.
For example, to duplicate the arm position in the follow-through (where many injuries occur) when throwing a ball, hold the Strength Bar with the arm out straight in front of you gripping the bar at the non-weighted end and with the shaft perpendicular. Keep the arm straight and then rotate by dropping the weighted end of the bar inward as far as possible and up and over to the outside as far as possible. Go through a full range of motion to fully strengthen the muscles involved. This exercise exemplifies specificity of rotator cuff exercises.
To strengthen the muscles with the arm out to the side extend a straight arm out to the side and then medially and laterally rotate the arm (this duplicates what many pitchers do in pitching). Do both arms to the same and opposite sides to strengthen the action on both sides. The more positions you create to mimic the positions that the arm is in during different throws, hits or catches, the more effective will be the all-round strengthening of the shoulder and arm muscles involved.
Note that if you bend the elbow the action will no longer affect the shoulder joint; it will be supination and pronation of the forearms. But, by keeping the arms straight and going through a full range of motion, you also strengthen the muscles involved in supination and pronation. Thus it is imperative that you keep the arm straight, in the same position with which you typically execute the skill.
However, doing supination/pronation exercises are also excellent for strengthening the elbow joint and prevention of injury to the elbow. This is especially true of players who are usually characterized as “wristy”. This means the player who relies greatly on the wrist action in hitting and, throwing.
Note that there are also other great exercises for specificity of the rotator cuff exercises, especially the medial and lateral that takes place in the shoulder joint. This includes the T-bench medial rotation and kneeling lateral rotation on an exercise bench. They are very specific to the actions that occur in pitching and quarterback throwing.
For more information on these and other exercises see Biomechanics and Kinesiology of Exercise