Introduction/purpose: Although metal baseball bats are widely believed to outperform wood bats, there are few scientific studies which support this. In a batting cage study, Greenwald et al. found that baseballs hit with a metal bat traveled faster than those hit with a wood bat, but the factors responsible for this difference in bat performance remain unidentified. The purpose of this study was to determine the effects of swing speed, impact location, and elastic properties of the bat on batted ball speeds.
Methods: The pitched ball, batted ball, and swings of two wood and five metal baseball bats by 19 different players were tracked in three dimensions at 500 Hz using a passive infrared motion analysis system.
Results: Increases in the batted ball speeds of metal bats over those of wood bats resulted from faster swing speeds and higher elastic performance with an apparent increase in the ball-bat coefficient of restitution. The contribution of these variables to batted ball speed differed with metal bat model. The "sweet spot" associated with maximum batted ball speeds was located approximately the same distance from the tip of wood bats as it was from metal bats.
Conclusions: The variables that correlated with differences between metal and wood bat performance, and most notably differences in the percentage of faster batted balls, were identified using a novel kinematic analysis of the ball and bat. These variables and their correlation with bat performance should be applicable to other players and bats, although more skilled players and higher performing bats would likely result in even faster batted ball speeds.