Baseball is a sport in which success is built on the ability of the athlete to replicate specific movements. Many baseball drills are situational; throwing, fielding, and batting practice are directed toward the player being conditioned to react to specific defensive and offensive situations. The physical attributes of hand-eye coordination, reaction time, and agility may be more important to success in baseball than in almost any other sport.
Pitching machines are a training aid designed to permit players to practice, hone, and refine their batting stroke without requiring the presence of a pitcher, or otherwise requiring a catcher to receive the batting practice pitches. Pitching machines are similar in their purpose to the simulators used in other sports, such as computer-supported bobsled trainers. The pitching machine is more limited in its application than some other sports simulators because the athlete is focused on one narrow aspect of baseball training in facing pitches thrown by the machine. The pitching machine does not require the athlete to engage in the entire sport skill set as would be required in an actual competition.
The history of the automated pitching machine suggests that there are a number of contenders for the title of inventor of the world's first such device. Many authorities confirm that Lorenzo Ponza (1918–2004) was the developer of the first portable on field pitching machine; Ponza created his machine in 1952 to assist in the development of Little League players (age 14 and under).
Baseball is a game with the fundamental objective of scoring more runs than the opponent. Two means to meeting this objective are batting practice, to enable players to hit the ball more effectively, and pitching, to limit the hitting of the opponent. No sport depends to a greater degree on the repetition of the elements of both pitching and hitting. The physical requirements of pitching are such that pitchers are the most injured players in baseball. At the youth level, when the pitching arm is not fully developed, serious injuries that result from overuse are common. The strain created by the forces directed into the pitcher's throwing elbow and shoulder, from the twist necessary to deliver a curve ball or a slider, restrict the number of pitches that should safely be thrown in any given training period at any age.
The striking with a bat of a round ball thrown at a significant velocity with spin imparted to it is a difficult task; at a major league level, a batter is deemed to be competent if he or she is able to hit safely three times out 10. For this reason, the most important feature of batting practice is the ability to replicate the game day swing of the bat as many times as possible. Pitching machines safely permit this replication without wear and tear on the pitcher's arm.
A pitching machine is typically employed with a related piece of equipment—the batting cage, an enclosed area usually forming a 90° angle with the apex behind the batter. The cage is entirely enclosed so as to prevent any batted balls from striking other persons. The pitching machine is positioned at precisely the same distance from the batter as would be the pitcher, to precisely simulate the pitched ball. Pitching machines are constructed as one of two types: a machine with an overhand arm delivery or one constructed with two horizontally opposed wheels, with the ball delivered by their rotation effect. The machine may be configured to simulate a baseball pitch, delivered overhand, or a softball delivery, delivered underhand.
Pitching machines permit both the speed and the spin imparted to the ball to be varied. For youth players, the ball might be delivered at speeds in the vicinity of 40 mi (64 km) per hour; for a professional player, the ball would be thrown at the speeds expected in major league play, a range from 80 to 100 mi (129-160 km) per hour. The machine can also be configured to throw fastballs, curveballs, sliders, and screwballs, the most common pitches thrown in the game. The practicing batter can face the same pitch for an indefinite period, practicing against it and endeavoring to remove any perceived flaws in the batting stroke.
The pitching machine and the companion batting cage are also an excellent venue for the batter to combine the physical work on the batting stroke with the mental sports training known as visualization. As each pitch is delivered by the machine, the athlete can imagine being in various game situations and attempt to strike the ball thrown by the machine in the same fashion as he or she would react to each pitch. The athlete can also visualize where various base runners might be at that point in the game, the number of outs, or the ball and strike count, to make the batting practice more realistic.