Progress in measuring the performance of baseball and softball bats

The performance of baseball and softball bats has improved markedly over the past four decades. This has motivated many associations to develop test methods and measures to regulate bat performance. The present study reviews the progress of laboratory bat performance tests. The test involves an initially stationary bat that is allowed to recoil after being impacted by a ball. Bat performance was shown to be insensitive to changes in the way the bat was supported and sensitive to the rebound ball and bat speed. The rebound ball and bat speeds were in turn influenced by air turbulence and bat vibration, respectively. The common technique of normalizing the bat–ball coefficient of restitution (COR), by dividing it by the ball COR, was shown to overcorrect by more than the original effect of ball COR. Normalizing bat performance for the effect of ball weight, on the other hand, reduced its effect on bat performance. Measuring bat performance in the laboratory at impact speeds representative of play conditions had only a small effect on the relative performance between bats, but improved the correlation with field results. While laboratory bat performance tests are complex and experimentally challenging, they are robust and repeatable. & 2008 John Wiley and Sons Asia Pte Ltd