The rash of arm injuries these days is epidemic...

Until high school my general understanding is that kids should not throw curve balls. That's accepted, somewhat, but you still see it.. not often.

Of our 4 starting pitchers the last two years in High School 3 have had surgery. All threw 'junk' in youth baseball.

Now the above is simply what I can say I know and have heard... I am NOT expert on young pitcher throwing arms and have read nothing about it. All my grandson's pitched RARELY... only in emergency situation, and all of them struggled to simply keep it down to 3 walks per inning. None of them pitch today.... wellllllll, almost never.

Yes, about the catcher knowing the pitch. I'm not sure how they were working that out.... maybe leaving the catcher unaware, maybe another signal? BUT... may not be needed.... these were Freshmen and Sophomore's.... even their curve balls don't really move a lot. - JamesJM