Shohei Ohtani's remarkable breaking ball, known as the "sweeper," exhibits a pronounced lateral curve while maintaining minimal vertical drop. This unique characteristic is attributed to the direction of the ball's rotational axis aligning with its trajectory.
Research teams used the Fugaku supercomputer to analyze it. Then on May 29, the Tokyo Institute of Technology revealed the secret hidden mechanism of this remarkable pitch. Their analysis showed the tilted axis of rotation also created an upward force on the ball, leading to its unique movement.
What is a Sweeper?
The sweeper gained recognition when Shohei Ohtani showcased it during the Japan national team's victory in the World Baseball Classic in March. And while a sweeper is a type of slider, a conventional slider curves with a gradual drop.
Analysis of Ohtani's pitching data also shows his sweeper is unique. It is a variety of slider that bends sideways but with a minimal downward trend. Why this phenomenon occurs remains a mystery.
Fugaku Analyzes Ohtani's Pitches
The research team utilized the Fugaku supercomputer to try to unravel the secrets. First, they calculated the surrounding airflow and trajectory of the ball by altering the rotation speed and angle of the axis of rotation.
Eventually, they tilted the rotation axis by 50 to 60 degrees in the batter's direction. As a result, this tilted axis generated an airflow that pushed the ball diagonally upward from behind. In this way, they were able to replicate Shohei Ohtani's pitches.
MLB.com has documented the use of the sweeper since the start of the 2022 season. According to the website, 99 MLB pitchers had thrown the pitch as of April 19, 2023.
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(Read the report in Japanese.)
Author: The Sankei Shimbun