There are several people I like that put their stuff on the internet, and Phil Rosengren of Better Pitching is one of them. Here's a great video where he lays out some tips on how to throw a curveball:
I love the grip he uses and the way he talks about keeping a firm wrist.
Especially for young kids, we cannot allow them to "turn the door knob" or twist that wrist inward when they throw a curveball, or any pitch. It's all about finger pressure and grip. From there, the angle of the forearm is the difference, not he wrist action.
I think kids should learn early on how to throw a curveball (let's face it, they're going to experiment when you're not looking anyway). They should be shown the correct way to throw the curveball to keep it healthy for their arm and to give them the best chance of having a great one as they develop.
The curveball is an awesome pitch, and one that can definitely increase a kid's chances of success on the mound. The 12-6 curveball is the one to learn, and it takes a long time to master it. I recommend keeping it your #3 pitch, meaning you should still spend most of your training time on your fastball command and changeup.
Master those two first the best you can, and work on the curveball third. Never forget that your secondary pitches are only as good as your #1. Get your fastball figured out to where you can locate it in any count and hitters won't have a chance when you do throw the curveball.
Coach Rosengren has a Curveball Mastery System that is really cool and worth checking out. It has all of the information and videos that you need to learn or teach the PROPER way to throw a curveball to players of all ages. Check it out here, we highly recommend it!
You may also want to read our article: When Should Kids Learn The Curveball
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