Since metal bats were introduced to college baseball in 1974, guidelines have been introduced to make them less lively.
After the home-run-filled 1998 College World Series, in which USC beat Arizona State 21-14 in the championship game, steps were taken to adopt a BESR (ball exit speed ratio) standard to reduce the potency of metal bats.
Since 2003, the BESR standards have applied to metal bats at both the NCAA and high school level. Due to the standards, the bats are heavier — lessening bat speed — have smaller barrels and balls come off the bat with the same maximum exit speed (97 mph) as the top wooden bats.
Still, it is widely accepted that metal bats are livelier.
For starters, metal-bat critics roll their eyes at the testing conditions used to determine the maximum exit speed of 97 mph. The conditions — a 70 mph pitch and a 66 mph swing speed — are much slower than typical conditions even at the high school level.
In addition, metal bats have qualities that make them more potent than wood. In metal bats, weight is distributed more evenly, so they are easier to swing fast. Metal bats, which are hollow, also tend to compress like a spring when striking a ball. This causes the ball to jump off the bat in what researchers have termed the “trampoline effect.”
Sonoma Valley High School coach Don Lyons often uses wood bats in practice. And he’s seen his players toss them aside during batting practice in favor of metal ones.
“There is concrete evidence to me in working with high school athletes who will hit with wood and switch to aluminum on the next swing,” Lyons said. “It’s decidedly different. The ball just comes off the bat harder with aluminum.”
University of Illinois physics professor Alan Nathan has done extensive research on the physics of the bat-ball collision and bat performance. He also serves on the NCAA Baseball Research Panel, an unpaid position in which he helps advise the NCAA on bat-performance issues.