A pitcher can choose to throw the ball at any angle in order to confuse the batter. However, it is very important to keep the hand behind the ball as long as possible to create the spin at the release point (Katt). This technique can be compared to cracking a whip. When a whip is cracked, the hand is kept behind the whip until the last moment, when it is thrown foreword. The air at the end of the whip is accelerated, thus emitting a "cracking" sound. Similarly, by keeping the hand behind the ball, then snapping the baseball at the release point, the spin of the ball will be maximally accelerated. The pitcher must literally snap his fingers at the release of the ball. As with cracking a whip, snapping the ball out of the hand will apply the maximum centripetal, or circular, force to the ball. With this key technique, a pitcher can throw one of the most elusive pitches in baseball.
A Knuckleball's Unpredictable Path
When properly thrown, a knuckleball "seems to make up its own rules on its way to the plate. It floats, flutters, twitches, lurches, and dives" (Flaste 364-365). This improbable behavior was once discounted as baseball lore, but "scientists have recently proven that a knuckleball can veer more than once in flight" (Flaste 364). While a successful curveball spins rapidly, "an effective knuckleball should be thrown so that it rotates less than once on its path to home plate" (Watts 960). It is this very slow rotation that is responsible for the erratic and unpredictable trajectory that has baffled physicists, as well as batters, for decades.
If baseballs were entirely smooth spheres, pitches with little or no spin would move through the air on a predictable and straight path. However, as with curveballs, the stitches interact with the air, "creating turbulence in the airflow" passing over the moving ball (Flaste 364). Scientists have confirmed that when a baseball "is thrown with very little rotation, asymmetric stitch configurations can be generated that lead to large imbalances of forces and extraordinary excursions in trajectory" (Adair 29). In other words, as the baseball slowly spins, different seam configurations are exposed to the flow of air around the ball, causing a disturbance or change in the air flow, which creates sudden changes in the ball's path. As one analyst notes:
At first, the seams' aerodynamic influence might be pushing the ball outside, away from the plate; then, suddenly, a small shift in the seams might reverse the force, causing the ball to plunge back across the inside (Flaste 366).
These deflections of the baseball are directly dependent on the amount of spin. If the ball rotates too quickly, it acts as a rough sphere with no distinguishable obstructions for the airflow to hit and move the ball. A ball with too much spin will simply follow the path dictated by the spin of the ball, and is very unlikely to overcome inertia and change its trajectory. The seams must slowly be exposed to air in order to create significant airflow disturbances. Too little spin is also problematic; without any spin, the ball "can only curve laterally in one direction. The maximum deflection will be dependent only on the initial orientation of the baseball" (Watts 963). Since the knuckleball's unpredictable movement depends on a change in the seam configurations exposed to airflow, a lack of rotation causes no changes in airflow and, subsequently, no movement. The precision required to throw a true knuckleball makes it one of the most difficult pitches to throw successfully.
Techniques Behind the Knuckleball
To throw a knuckleball, follow these four main steps:
1. Fingernails -- Grip the baseball by clenching it just below the seams with the tips of the middle, index, and ring fingers. Dig the fingernails deeply into the ball.
2. Thumb Position -- Place the thumb below the ball to give it support while keeping the pinkie off to the side.
3. Stiff Wrist -- Throw the ball with a stable and stiff wrist to eliminate as much spin as possible.
4. Extend Fingers -- Extend all fingers toward home plate in a pushing motion as the ball is released.
Contrary to what the name suggests, today most pitching instructors and experts recommend gripping the ball with the fingernails or fingertips instead of with the knuckles. The ball should be "pushed" at medium speed (55-72 miles per hour) toward the plate as if throwing a shot put. If correctly thrown, the ball should rotate between one half and one full rotation along its path. This is no simple task; it takes years of practice to throw a knuckleball consistently.
