In the wake of the World Series, many hopeful young players will head to the batting cages to emulate the swings of major leaguers with one key difference: They will use metal, not wooden bats. But according to a new biomechanics study conducted in part by University researchers, the performance of metal and wood are comparable in youth baseball.
For youth players, bat composition — metal versus wood — does not substantially affect baseball speed, according to an Oct. 15 article in the Journal of Applied Biomechanics. The Orthopedic Department at Alpert Medical School and Rhode Island Hospital researchers analyzed the swings of 22 baseball players ages 13 to 18. Each player swung 13 different bats: three wood, nine composite and one aluminum. The non-wooden bats were as much as 7 oz lighter than the wooden bats.
Whereas similar studies have used radar guns to track the speed of the ball, this study tracked the motion of the bat and ball in three dimensions over time, using multiple cameras shooting 300 frames per second, said J.J. Crisco, professor of orthopedics and lead author of the study. This setup, which took place in an indoor batting cage, allowed the scientists to monitor the motion of both the ball and the bat.
Three primary factors — swing speed, trampoline effect and moment of inertia — affect bat performance, Crisco said. The trampoline effect, measured by the ball-bat coefficient of restitution, refers to the elasticity of the barrel of the bat or how “the barrel of the bat deforms,” Crisco said. The moment of inertia is a measurement of the distribution of mass along the bat, he added.
The paper revealed that the greater trampoline effect of lighter metal bats — their tendency to greatly deform when they hit a ball — is not necessarily an advantage.
“For these youth players, even though light bats had a high trampoline effect, they still did not hit the ball significantly faster,” Crisco added.
The study supports a theoretical assumption that had been circulating in the field, said Alan Nathan, professor emeritus of physics at University of Illinois at Urbana-Champaign.
“Lighter bats are not necessarily better bats,” he added, noting a tradeoff between moment of inertia and trampoline effect.
Nathan added that in the past, more baseball-bat collision research has been done on collegiate bats than youth bats. He said this could be attributed to the fact there is a wide range of moments of inertia possible in youth baseball bats. Collegiate bats’ designs, on the other hand, are restricted by the drop-three rule. This regulation dictates a relationship between bat length and bat weight — specifying that the difference between the weight of the bat in ounces and the length in inches must be no more three.
There are noticeable differences in using metal and wooden bats, said Nick Fornaca ’15, an infielder on Brown’s varsity team.
“One of the biggest differences is that wood bats break pretty often,” he added.
Fornaca said he played little league baseball using metal bats similar to those in Crisco’s study.
Though stringent regulations on bat weight and length exist for high school and collegiate baseball, no such standards are in place for youth baseball, Crisco said. Players can use very light bats, which allow for faster swing speeds.
This study has an advantage over similar studies because its subjects were humans not robots, Crisco said. Live players offer more variation in swing style and speed, while robots are limited to one motion.
The study’s results could be used in formulating youth baseball bat regulations, Crisco said.
“Our data (say) you can use a really light bat as long as the trampoline effect is reasonable,” he added.
The study was funded by the National Operating Committee on Standards for Athletic Equipment and USA Baseball, the governing body for amateur baseball.
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