For this latest batting cage study, Smith et al. recruited 52 young 12-year-old athletes (51 male, one female) and asked them to swing three different commercially available baseball bats in two different weights—six bats in all. One type was solid wood typical of the bats used prior to 1970; one was a hollow design like the bats adopted by most youth leagues in 2000 (the BPF 1.15); and the third was the USA Baseball hollow design adopted in 2018. All the bats were painted black to hide the make and model in order to reduce perceptual bias. Each bat had several spherical reflective markers, the better to track the bats’ motion with high-speed infrared cameras. The baseballs were wrapped in reflective tape for the same reason.
The balls were pitched underhanded and at lower speed to increase the batting averages of the participants, and each batter swung each of six bats five times. The batters were divided into alternating groups of four to minimize fatigue. A total of 1,512 swings were recorded, and the team used that footage to measure the speed of the swings and the balls’ exit speeds.
Smith et al. found that balls hit with the BPF 1.15 metal bats had higher exit speeds than the wooden bats—an expected finding, since youth leagues stopped using these bats precisely because of that performance advantage. The ball exit speeds with USA Baseball bats fell halfway between the BPF and wooden bat speeds. They determined that the exit speed depends strongly on the bat-ball coefficient of restitution and a player’s swing speed, while swing speed in turn is strongly dependent on the bat’s inertia. Thus, the team concluded that a metal bat should take into account those two parameters (coefficient of restitution and inertia) to affect exit speed.
That said, ultimately it comes down to the athletic skill levels of the players. “If you’re really trying to hit the ball far, you’re going to get a much bigger payoff by working out and getting stronger, especially if you’re a young kid and growing fast,” said Smith. “That’s going to have a much larger effect on how hard you hit the ball, than on what bat you buy.”
Journal of Sports Engineering and Technology, 2024. DOI: 10.1177/17543371241260098 (About DOIs).
