Rafael F. Escamilla1, Ph.D., Glenn S. Fleisig2, Ph.D.,
Steven W. Barrentine2, M.S., James R. Andrews2, M.D., and Kevin P. Speer, M.D.
Pretty impressive group. They reviewed the studies and concluded that overload/underload training resulted in significant improvements. But I'm sure they're not as qualified as Chris.
"Data from these training studies strongly support the practice of training with overweight and underweight baseballs to increase throwing velocity of regulation baseballs."
Typically an average HS pitcher will gain about 1 mph at most in a 12 week period. Some more, some less but on average about 1 mph. These pitchers gained significantly more while performing overload/underload training over periods ranging from 6 to 12 weeks. The studies showed pitchers gaining an average of 3 to 5 mph with the younger pitchers (HS) gaining a bit more on average than the older ones. If there is some other type of training the control group could have been doing that would have made the type of gains the overload/underload training did I'd like to see it because as a group pitchers don't make those types of gains with any other training I've ever heard of. Anecdotally I've heard of gains from long toss, but to my knowledge no studies have been done to prove it. I do prefer long toss, but that is just a personal preference.
I'm sure that weighted ball training didn't help Steve Ellis either, he would have picked up that extra velocity by just sticking with his routine. Right.