First-ever quantification of fingertip slippage during baseball pitching

In baseball pitching, "slipping" as a result of different types of balls and grip-enhancing agents has been considered an important issue, which has been actively discussed. However, previous discussions were based on players' subjective sensations, and it was not fully understood whether the ball actually slips during the release process, to what extent it slips, and how differences in slip distance affect pitching performance.

A research group led by Professor Takeshi Yamaguchi, Associate Professor Toshiaki Nishi, and Graduate Students Souta Suzuki (at the time of the research) and Shinnosuke Suzuki from the Graduate School of Engineering at Tohoku University, along with Research Scientist Daiki Nasu and Visiting Research Scientist Takehiro Fukuda from NTT Communication Science Laboratories, captured the movement of fingertips and the ball during fastball (four-seam) pitching using a high-speed camera and revealed the slip distance between the two during the release process under different friction conditions. They also clarified the relationship between slip distance and pitching performance metrics such as ball speed, spin rate, and control. Their research was published in Scientific Reports.

The team developed a method to estimate slip distance from the ball's rotation rate and the movement of the fingertips relative to the ball center during the ball release process. In all conditions—no application, water, rosin powder, and pine resin spray—slight slippage occurs immediately after the ball leaves the thumb. Subsequently, except when wet with water, slippage was suppressed as the fingers catch on the seam. They found that using rosin or pine resin spray allows the fingers to catch on the seam longer, resulting in shorter slip distances. On the other hand, when the fingers were wet with water, they did not catch on the seam, causing slippage throughout the release process, showing more than twice the slip distance (averaging 22 millimeters) compared to when using rosin or pine resin spray. This clarified that grip-enhancing agents like rosin effectively suppress slippage during pitching. They also found that as slip distance increases, ball speed and spin rate decrease, and the ball tends to reach higher positions. In particular, spin rate decreases significantly with increasing slip distance.

This study is the first to focus on the slippage between fingertips and ball in baseball pitching, which had previously only been discussed subjectively, and to quantify slip distance and differences due to friction conditions. It contributes to understanding the mechanism of ball release under different friction conditions and is expected to lead to improved pitching performance, pitcher injury prevention, and equipment development.

Additionally, although pitchers were instructed to throw at a constant velocity (130 km/h), ball velocity significantly decreased in the water application condition compared to the rosin application condition. This is thought to be because pitchers perceived fingertip slippage and adjusted their pitching motion. In the future, the researchers plan to clarify changes in pitching motion due to changes in friction conditions through analysis of whole-body movement and muscle activity, and to develop pitching motions that maintain performance even with slippery balls and reduce the risk of injury.

Journal Information
Publication: Scientific Reports
Title: Impact of slip distance between fingertips and ball on baseball pitching performance under different friction conditions
DOI: 10.1038/s41598-025-93632-y