Bill Hezel Profile picture
16 Oct, 12 tweets, 4 min read
THREAD: Pretty common place in baseball to hear a coach tell a pitcher that it is important he repeat his delivery. We have all probably heard this before. Many coaches are quick to link the ability to repeat the delivery to command or a pitcher's effectiveness.
Back in July I decided to ask for help from our R&D team to investigate this a bit further. @dan_aucoin13 and @kylelindley_ were able to do some initial digging on this very subject.

First, does more mechanical variability correlate to poor command?
We investigated a list of specific metrics obtained via motion capture and looked at the standard deviations of the three throws we analyze during that process.
As expected, there were no strong relationships between less repeatable mechanics and worse command. However, diving a bit deeper, there were some weak correlations.
Variability in torso rotation at FP was negatively correlated with command meaning more variability was associated with worse command.
Variability in front knee flexion at FP and BR were positively correlated with command, while variability in maximum front knee extension velocity was positively correlated with command.
Important to note, as @kylelindley_ explained to me, even with the relationship between torso rotation and command, the resulting r value suggests that it only explains less than 2 percent of the variance in command, which isn’t much. It would seem there is not much here at all.
@dan_aucoin13 took this a step further and looked at some of those same metrics and how they correlate to Stuff and intrinsic run values.
Variability in max elbow flexion was moderately correlated to better Stuff. Variability in shoulder abduction at FP was moderately correlated to better Stuff and better IRV. Variability in Shoulder ER at FP was weakly correlated to better Stuff and better IRV.
Finally, variability in torso rotation at FP was moderately correlated with worse Stuff and worse IRV.
Important to note, there were some limitations to this investigation. Primarily, that this was not a paired data set. I still think it is pretty safe to say, pitching is hard. The throw is a very complex movement.
Much more likely goes into having nasty stuff and commanding the baseball than simply repeating the same mechanics over and over again. We still have a lot to learn about how the throw works and how that actually impacts pitch quality.

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