However, the young players also lost range of motion in what's called "internal rotation" (moving the arm in the opposite direction, as in letting a pitch go) . . .
Malachy McHugh, director of research at the Nicholas Institute of Sports Medicine and Athletic Trauma at Lenox Hill Hospital in New York City, said the movements involved in throwing a ball appear to have different effects on flexibility. "The loss of internal rotation is probably related to deceleration after you release the ball.
I'm no orthopedist, but it seems like a dandy solution for this is to simply have young pitchers extend their follow-throughs to decrease the jolt of deceleration. How? I dunno. How about running forward after each pitch? Yeah, we may lose a few to batted balls, but I bet it cuts down on arm injuries!