It's Just Physics
Every other week I write an email discussing what I learn launching and growing Reboot Motion. If you would like to receive it directly in your inbox, subscribe below.
The following is the first post in a series on the Wake Forest Bridge Seminar, which was put on by Mike McFerran and Wake Forest Baseball Dec 17th and 18th 2022.
While nothing matches being there, I wanted to share what I learned for those who missed it, and to set the stage for an ever bigger turnout in 2023.
(This first post may be a bit self serving, as Reboot’s own Jimmy Buffi is the presenter.)
It’s Just Physics
When analyzing pitchers, people regularly talk about movement efficiency- Jimmy uses that term literally. As he explains, if the goal is to increase velocity, we have to understand causation. And causation comes down to two things:
How much energy the pitcher generates, and
How much of it they transfer form the ground, through their body, to the ball.
In his view, people too often are drawn to a single metric, while they’d be best off taking a holistic view on how energy is first created, then transferred.
It Starts with the Ground
Step 1 is getting energy into the body. And that happens via ground reaction forces.
As Jimmy explains, ground reaction forces do not determine velocity. Rather, they set a pitcher’s potential.
While increases in ground reaction forces should correlate with greater velocity, whether or not they do depends on what happens next.
Then, It’s About the Transfer
Once momentum enters the body, the pitcher’s job is to get as much of it as possible to the ball. While this may be an oversimplification, there are three major factors:
First, sequence. If the goal is to transfer momentum from the ground to the ball, there is an ideal path for it to pass through the body.
Second, direction. While I sometimes get lazy when writing and use energy and momentum interchangeably, momentum is a superior metric because it accounts for direction (and mass). Jimmy explains below:
Third, ranges of motion. The definition of work is force applied over a distance. When an athlete increases their range of motion, they increase their distance, allowing them to do more work.
Finally, It’s About the Ball
After a pitcher has created ground reaction forces and transferred momentum from the ground through their body, the final step is getting that momentum from the pitcher’s throwing hand- and even more specifically from their fingers- to the ball.
Generally, we see high correlations between the spin direction of the body and the spin direction of the ball, which hitters likely pick up on to predict movement prior to ball release.
However, what is generally true is not always true. We believe mismatches in these two spin directions is an area for the often discussed, never truly defined term “deception”.
The Value of Thinking Holistically
When analyzing movement, we need to understand both the uses and limitations of what we are looking at. In other words, data are a tool- not the final answer. We can’t let numbers replace thought.
Physics tells us:
All else equal, increasing ground reaction forces should increase velocity.
All else equal, transferring momentum in the correct sequence is better.
All else equal, aligning rotation planes makes pitchers’ more efficient.
All else equal, increasing ranges of motion allows pitchers the opportunity to do more work.
But pitchers don’t pitch in a vacuum. Coaches can’t coach that way. And analysts can’t analyze that way.
The best work is done when a pitch is viewed as a holistic process where the athlete generates ground reaction forces, transfers them through the body, and eventually to the ball.