Just before game time, Detroit Tigers clubhouse manager Jim Schmakel makes sure a long, dirt-stained canvas bag is unloaded in the on-deck circle.

Among other things, it holds a 10-ounce, hard-clay sleeve that slides onto the bat; a 50-ounce weighted bat made of wood and plastic; a half-bat, half-pipe contraption, 96 ounces, with a sliding weight resembling the pendulum weight on a metronome; and an old-fashioned 20-pound sledgehammer.

Almost...