Field Measurements of Softball Player Swing Speed

The bat swing speed is one of the most important factors affecting bat performance. The equipment needed to measure swing speed is sophisticated and has high data reduction overhead. For this reason, relatively little data exist describing bat motion in field conditions. The following describes results of one of the most ambitious swing speed studies ever conducted. The study involved bats of nearly constant weight and varying inertia that were swung by 29 adult batters. The study was conducted using right handed batters on a regulation outdoor field with a live pitcher. Swing speed was measured by tracking markers on the bat with two high speed video cameras. The cameras were arranged and calibrated so that the bat markers could be traced in three-dimensional space. The ball's pitch speed, hit speed and inclination were also tracked and compared to a three-dimensional Doppler radar system. Comparison of the video and the known bat marker spacing showed an accuracy of 6 mm. The bat center of rotation during impact was close to the knob of the bat, while bat swing speed tended to increase with decreasing bat inertia. Bat swing speed was also shown to depend on the batter skill level. The results will be used to improve relations regulating bat performance.