Ground Reaction Forces PitchingGravity is the force that attracts a body toward the center of the earth. An athlete must react with the ground to oppose this gravitational force to move his body, therefore better athletes build more ground reaction forces to generate more speed/power. High velocity pitchers are no exception!
How can any pitching coach or instructor say that the pitching delivery starts and continues with the hips? The hips are not reacting with the ground. How can any pitching coach or instructor say that the pitching delivery starts with the lift leg? The lift leg is not reacting with the ground. Why isn’t every pitching coach and instructor coaching or instructing the pitcher to start with the drive leg? The reason, because they do not know the science behind high velocity pitching.

The Science Behind the High Velocity Pitcher

A study called, Characteristic Ground-Reaction Forces in Baseball Pitching showed all the evidence that the push-off and braking forces of the lower extremities correlated highly with ball velocity. The study was performed by Bruce A. MacWilliams, PhD, Tony Choi, Mark K. Perezous, MD, Edmund Y. S. Chao, PhD, and Edward G. McFarland, MD from the Department of Orthopaedic Biomechanics and Section of Sports Medicine and Shoulder Surgery, Johns Hopkins University, Baltimore, Maryland.
This was the first study of its kind to document the effects of ground reaction forces for both of the lower extremities. This would be the drive leg and the landing leg of the high velocity pitcher.
Here are the results from the study:

On average, the force component in the direction of the pitcher (Fx) for the push-off limb exhibits a gradual increase until just before foot contact, reaching a maximum of 0.35 BW
Landing anterior-posterior (AP) shear increases rapidly after foot contact and reaches a maximum of 0.72 BW just before ball release….
The vertical force component reflects body weight support. Push-off vertical forces are fairly constant, with peak magnitudes of slightly more than 1.0 BW occurring early in the pitch cycle. Landing vertical forces are gradually built up after foot contact to approximately 1.5 BW, peaking just before ball release….
The push-off resultant was relatively constant at about 1.0 BW until just before foot contact. Landing resultants increased gradually from foot contact to just before ball release, reaching a maximum of about 1.75 BW….
At the point of maximal external rotation of the arm in cocking, the peak vertical forces (1.5 BW) and peak braking forces (nearly 0.75 BW) were generated….
Linear wrist velocity at ball release correlated highly with maximal push-off AP shear force, with vertical and resultant push-off force at the time of maximal anterior push-off force, and also with landing AP shear, vertical, and resultant forces at ball release.
You can read the entire study here:

Ground Reaction Forces PitchingIn summary, this data is contradicting conventional wisdom and advising the low velocity pitcher that he must first generate a lateral force in the drive leg of up to 35% of his body weight. This will occur if the pitcher focuses on aligning the Force Vector in a linear position before his weight shifts to his front side. Following this lateral force, the pitcher must implement a vertical force that is equal to his own body weight, which occurs during triple extension (3X) of the drive leg, peaking this vertical force just before front foot strike (View picture above).
Proceeding this drive leg force production the next event is stabilizing or braking the landing leg following 3X with a force up to 75% of his own body weight, while extending the front leg (2X) and generating a vertical force around 150% of his body weight. Both the braking force and the vertical force (2X front leg extension) of the landing leg must peak before pitch release, specifically during full external rotation of the throwing arm as defined in the case study (View 1st picture here).
The purpose of these ground reaction forces for the high velocity pitcher is to create a reactive launch into the upper extremities through the hips similar to a whip or more specifically a catapult system. The 3X Extreme Pitching Velocity Program seamlessly defines the sequencing of these events up the kinetic chain into this launch.

The Critical Timing Factor of the Pitchers Ground Reaction Forces

The study above made it clear that the timing of the ground reaction forces were the difference between a high correlation to ball velocity or not. To help understand this critical timing factor here is another key case study called, Timing of the Lower Limb Drive and Throwing Limb Movement in Baseball Pitching. This study was performed by  Bruce Elliott, J. Robert Grove, Barry Gibson. Here is the results from the study:

However, the slower group produced their peak resultant force earlier in the action, thus reducing the ability to drive over a stabilized front leg.
Read the entire case study here:

The first study listed above also supports these finding by saying that the “push-off forces were gradually built up during the windup, and peaked before foot contact.” 3X Pitching calls this critical movement the 3X Burst.
Here is even one more study making this point by defining the errors that will occur if timing is off and ground reaction forces are limited. The study was called, Characteristic Ground-reaction Force In Beginner Baseball Pitching. It was performed at the Department of Sports Medicine, China Medical University, Taichung, Taiwan. Here is an excerpt from this study that makes this specific point:

The pitcher keeps his center of gravity over his back leg to allow generation of maximum momentum once forward motion is initiated. If the pitcher’s body and momentum fall forward prematurely, the kinetic chain will be disrupted and greater shoulder force will be required to propel the ball at top velocity.
Read the entire study here:

The point of this excerpt is that if the initial move is poorly timed and ground reaction forces are not effectively implemented then a premature fall into front foot will causes a major disruption in the kinetic chain, which forces the shoulders to generate the forces the legs could not.
To understand how destructive this error is to pitching velocity and arm health, a case study by Kibler WB and Chandler J from the publication The Kinetic Chain in Overhand Pitching, defined the math illustrating this loss of kinetic energy from the stride and the load the shoulders are forced to carry because of this loss.

Kibler and Chandler calculated that a 20% decrease in kinetic energy delivered from the hip and trunk to the arm requires a 34% increase in the rotational velocity of the shoulder to impart the same amount of force to the hand.
Source of reference: Kibler WB, Chandler J. Baseball and tennis. In: Griffin LY, editor. , ed. Rehabilitation of the Injured Knee. St. Louis, MO: Mosby; 1995:219-226.
Read the entire publication here:

These percentages make a clear point that a pitcher must work hard to develop lateral and vertical ground reaction forces, at or above his own body weight, at the right time, to not only generate high pitching velocity but to reduce the stress on the shoulders, which could eventually lead to a career ending injury.

In Conclusion

All of these studies together illustrate the absurdity of coaching the pitcher to begin the delivery with anything other than the drive leg foot. Yes, we start the movement by leading with the hips but this is only to support the lateral forces and mainly to position the drive leg for building peak vertical ground reaction forces just before front foot strike. By not starting the delivery with the focus on the drive leg foot puts the kinetic chain in a position for poor timing, especially when focusing on the hips or the lift leg to build the stride.
Here is a case study from 1985, which first defined and documented the critical importance of beginning the pitching delivery with the drive leg foot. Here is the reference from the study summarizing the sequence:

Pappas AM, in his case study called, Biomechanics of baseball pitching. A preliminary report, described the pitching delivery as sequential activation of body parts through a link segment beginning with the contralateral foot and progressing through the trunk to the rapidly accelerating upper extremity. Improper mechanics or injury that alter this complex chain of events will in turn produce additional stresses in other links of the chain.
Read the entire study here:

Contralateral foot means the opposite side of the body, which is the drive leg foot.
All these studies together mainly prove the importance of the stride phase to generating pitching velocity. More importantly the importance of the bodies interaction with the ground through the drive leg foot and the landing leg foot and also the timing of this interaction.
The only negative that came out of the original study listed above, which can ultimately be turned into a positive later, is listed here:

Players exhibited trends similar to the group, with wrist velocity increasing with increasing forces. Others demonstrated an opposite trend, with higher forces correlating with diminished velocities. This difference suggests that there may be an effect of attempting to overthrow, with loss of velocity resulting from attempts to generate unnaturally high push-off forces. This anecdotal information suggests that pitchers should train to develop powerful leg drives as a normal part of the throwing motion, but they should not attempt to over-push to gain extra velocity.

This is proof that you can have too much of a good thing. The problem is the over-push when trying to generate ground reaction forces. It potentially can cause the bodies antagonist and protagonist muscles to both fire at the same time. This will reduce performance by reducing force production and restricting range of motion (ROM) because if both the antagonist and protagonist muscles are contracting then they are working against each other. Timing is the critical factor here. This timing involves firing the right muscles at the right time. Firing the right and wrong muscles at the right or wrong time will ultimately have the wrong effect.
The original case study leaves us with some important advice on how to improve ground reaction forces to support high pitching velocity and arm health.

Based on this study, strengthening of the lower extremities could be inferred to be important both to enhance performance and to avoid injury.

3X Extreme Pitching Velocity Program advises and implements a full spectrum of critical lifts and exercises especially the Olympic Lifts for strength and power training because it not only enhances force production but the timing of this force production, which we have learned these two factors together or the key to high pitching velocity.

3X Pitching Podcast Episode 3

The third episode of the 3X Pitching Podcast covers this article. Check it out!

Pitching Velocity Show – Episode 3 Transcript