You're skeptical about any study that has ever been completed , so this is not surprising. Also, size and speed are all relative. Sure, 10 year olds aren't hitting with the same force as 20 year olds. However, if you get knocked to the turf and bounce your head off it at a relatively high speed, you can end up with the same effects, especially with brains that aren't fully developed and neck muscles that aren't strong enough to prevent violent whiplash. Watch this video and tell me there aren't violent collisions in youth football.