Ah, the unquenchable thirst for more speed…every pitcher has it, as does every pitching coach. Achieving it, however, takes more than desire, more than solid pitching mechanics; it takes highly developed physical capacities and a true understanding of how the body works. Underneath each pitcher's unique flair and each coach’s pitching style, there are some very specific things that a windmill pitcher's body MUST be able to in order to generate maximum pitch velocity.
Reaching that coveted 65 to 70+ mph speed range is all about generating as much lower body force as possible at the beginning of the pitch, then stabilizing the body in a way that allows that force to be transferred through the torso to the pitching arm. Think of the whole pitching motion as the crack of a whip: first there is a forceful forward movement, followed by a sudden stabilization of the handle which sends a shockwave through the body of the whip to produce a sharp, high speed crack at the end. We're going to take a look at how the muscles in the human body produce force, and exactly how these forces need to align to produce a fastball that lights up a radar gun.
Muscles can work in three ways: eccentrically (stretching and lengthening), concentrically (shortening to overcome an external force, i.e. lifting or pushing), and isometrically (stabilizing, or holding the body in place). All three of these muscle capacities are absolutely crucial to performing an optimal windmill pitch, and they must be highly and equally developed in order to reach maximum velocity.
Additionally, ground reaction force (GRF) has an enormous role in the windmill pitch. This is where Newton's Third Law—for every action there is an equal and opposite reaction—comes into play: when you push off the ground to begin a pitch, the earth pushes back into your leg with equal force. Since the earth is immovable, that force propels you away from it.
A pitcher must begin by rapidly accelerating forward away from the pitching rubber generating as much lower body force as possible right from the beginning—initiating the “whip.” In their study, Characteristic Ground Reaction Forces in Softball Pitching, researchers Chenfu Huang, Li-I Wang and Chen-Ju Chien used force plates— devices designed to measure forces exerted by athletes during jumping and stepping actions—to measure GRF in a group of windmill pitchers. They determined that the pitchers who pushed off the ground with the greatest impulse (most force applied in the least amount of time) recorded the highest pitching velocities. If we think about it simply, this makes perfect sense: the harder and faster you push into the earth, the more force the earth transfers back into your body. Pushing off the ground engages concentric muscle action in the legs, and developing that capacity will improve the force with which you can propel yourself forward.
Next comes the stabilization phase. A tremendous transfer of force needs to take place the moment the stride foot hits the ground—the stabilization of the handle followed by the “shockwave” in the whip analogy. The pitcher needs a strong, sudden engagement of eccentric and isometric muscles to rapidly decelerate and stabilize the lower body and torso in a way that allows the force already in the body, along with the additional GRF generated by the impact of the stride foot, to be redirected from the stride leg, up through the torso, and out the pitching arm into the ball.
A lot can go wrong in the instants following stride leg impact. In order for all the force to be properly redirected into the pitching arm, the pitcher must achieve optimal body alignment. The hip of the stride leg must remain stacked over the knee, and the torso must be able to stop its forward momentum and support itself in a natural upright posture. If this posture breaks down in any way—a lean forward, a bend at the waist, a collapse of the drive leg, etc. (all common faults in windmill pitching mechanics)—the force is misdirected and the pitcher loses velocity. Therefore, a pitcher MUST develop the stabilizing power of her core muscles, and especially her gluteal muscles, in order to achieve maximum velocity.
Finally, the “crack” at the end: the transfer of force from the lower body up through the torso must trigger the acceleration of the pitching arm. Optimal body mechanics add up to nothing if the pitcher slows down her arm in any way leading up to the release of the ball.
The whip analogy not only describes the transfer of energy from the push off the rubber to the stride foot impact up through the body and into the arm, but also the action of the arm itself, which has its own secondary whip. As the hand approaches the release zone, the upper arm begins to stabilize, sending a shockwave of force through the forearm, to the wrist and hand, and out into the ball.
A hard the push off the ground + a quick, well-aligned stabilization of the body upon landing + arm acceleration = Maximum Pitch Velocity.
Practice alone, however, will not get a pitcher all the way to her speed goal. Strength training to develop the three muscular capacities—eccentric, concentric, and isometric action— must be part of the equation if pitchers want to raise the numbers on the radar gun.