Opinions on Use of Connection Balls in Training Mechanics


Does anyone have experience and/or opinions on the use of connection balls in working on pitching mechanics? When my son (15 years old) pitches, he brings the ball all the way down by his back knee (arm almost totally straight) then kind of “casts” it back a bit before bringing it forward. As a result, his arm is nowhere near “fully cocked” when his front foot plants. I’ve seen some folks on this forum refer to it as “flat arm syndrome”. If his motion was more compact, I think his arm would be more in sync with his lower body. It seems like connection balls would help with that. Any thoughts?