Theoretically since you would have more muscle fibers grouped in more ways, having extra muscle mass allows you finer control over your movements.
Of course its impossible for your muscles to be that discriminating, which is why really bulky guys have a harder time with fine movement. Even a small increase in regulators trigger a lot of muscle movement then.

But I could see where adding muscle could help with control, as well as velocity.

Strength and conditioning still matter after your body is grown, though.

Movement, control, location, pitch selection, etc. are certainly more important for the 21yo than for the 14yo, but you still need velocity (and health) as a base upon which to build those things. If a training regimen allows you to maintain and improve your strength and conditioning while avoiding injuries, it isn’t hard to see how that makes you a better pitcher.

I will say that, in my efforts to understand why Jaeger is so controversial, I find that all of the writing on the topic is full of fuzziness. The talk of “over-molding” and “specificity” in this piece is a good example. Another example: “it’s our job as coaches to find the biggest window of adaptation a pitcher has and bring it up to speed – while simultaneously keeping other qualities in mind.”

What does “window of adaptation” really mean? That “other qualities” are you keeping in mind? Why don’t you just tell me what you mean, instead of leaving me to fill in the gaps like that?

The central message I take from this piece is that the author believes long toss programs can be used to build arm strength (and thus velocity) in ways that target the activity of pitching more than weight training but remain safer than endless bullpen sessions. That seems reasonable, but it’s just the author’s belief… and it is couched in all kinds of vaguery that leaves me feeling suspicious.

Maybe I just need to ignore that other stuff, but the constant proselytizing (and the imprecise language that that entails) somehow leaves me feeling skeptical.