The Impact of Pronation and Supination Bias on Pitch Design
Recently, I made an X post talking about pronation and supination bias in pitchers and how it affects pitch design. Without being limited to X’s 280 character limit, I’d love to dive deeper into this topic.
X Posting on Pronation / Supination Bias
A quick reference for those who may not be as familiar, let me explain the two differences:
Pronation Bias:
A pronation bias in pitchers refers to an excessive inward rotation of the forearm during the throwing motion.
Supination Bias:
Supination bias in pitching refers to a pitcher's tendency to rotate their forearm outward (supinate) during the throwing motion.
* It's important to note that during the deceleration phase of a throw, both types of pitchers naturally pronate. However, supination-biased pitchers tend to delay that pronation slightly compared to pronation-biased pitchers, which can affect pitch movement.*
How does this affect pitch design?
When looking at various pitches, each athletes bias can serve as a suggestion for what pitch you may want to start with.
Pronation: These pitchers tend to have a better success rate throwing pitches that move arm side, and firm cutters. Often times, when these pitchers try to throw breaking balls, they wont be as firm and typically don’t generate as much glove side movement that supinators can.
A perfect example of a pronator in the bigs would be Max Scherzer. Max is able to generate significantly above average movement on his Changeup (15 Horizontal Break / 1.2 Induced Vertical Break at 83.8mph), Cutter (-1.5HB / 6.3IVB at 88.4mph) but both of his breaking balls would rank fairly below average shape wise Slider (-3.5HB / 0IVB at 84mph) and Curveball (-15.6HB / -12.4IVB at 75.4mph). While both of these pitches are still very effective, neither of them would be considered above average movement or velocity.
Supination: These pitchers tend to have a better success throwing pitches move glove side, and tend to be able to throw multiple efficient breaking balls. Traditionally these pitchers will struggle throwing pitches that move arm side. The outlier to the arm side movement would be those who are able to dig into seam-shifted wake pitches, but that would be a heavy outlier.
A great example of a supinator would be Gerrit Cole. Gerrit is able to get his his Slider at ( -4.9HB / 0IVB at 89.1mph), and Curveball (-10.6HB / -16.5IVB at 82.9mph). His slider sits 5mph harder and -1.4 inches of HB compared to Scherzer, and his curveball is 7.5mph firmer and a much cleaner depth shape that Scherzer’s. With that being said, Cole doesn’t even throw a Sinker, and his Changeup is very below average shape wise at (14.8HB / 8.9IVB at 89.1mph) while its pretty firm, its not a very ideal shape.
It's evident that using pronation and supination bias for pitch design advantages doesn't guarantee absolute outcomes. As we can see with Scherzer’s SL/CB and Cole’s CH, these pitches still yield effective results. A pitcher with a pronation bias can still effectively throw pitches typically associated with supination bias, and vice versa. What's crucial is to consider the desired pitch shapes, velocities, and usage frequencies. For instance, a pitcher with a supination bias may struggle to throw a heavy run changeup, while a pronation-biased pitcher might find it challenging to execute a heavy sweeper with minimal vertical break.
It's worth noting that Gerrit Cole throws his changeup less than 5% of the time, and Max Scherzer throws his slider and curveball less than 30% combined. Frequently throwing pitches that deviate from your natural bias can increase the strain on your arm. Therefore, understanding your body's motor preferences and tailoring your pitch repertoire accordingly is essential for long-term pitching success.
Sources:
https://www.washingtonpost.com/sports/dialing-back-the-max-nationals-seek-to-manage-the-relentless-scherzer/2018/03/19/b10bea36-2b9e-11e8-8688-e053ba58f1e4_story.html
https://sports.yahoo.com/yankees-ace-gerrit-cole-pitches-182141474.html
https://examination.lexmedicus.com.au/collection/wrist-hand
https://pitcherlist.com/player/max-scherzer/
https://pitcherlist.com/player/gerrit-cole/
Great stuff here!