Safety of throwing "all arm" (contrarian opinion)

It’s commonly believed that young pitchers who throw “all arm” are stressing their arms more than pitchers who put the whole body into it, whose arms are “just along for the ride”. I’m inclined to take the opposite position.

My son (age 9) is currently recovering from “Little League Shoulder” (shoulder growth plate injury). He is about to start a rehab program that will include some video for the physical therapist to check his mechanics. My ortho doc, who has never seen him throw, suggested that part of the problem could be that he is throwing too much with his arm, and ought to be putting his whole body into the effort.

The only thing is… compared to kid pitchers his age that I’ve seen, he puts his whole body into it very well. His arm really is “just along for the ride”… (but what a rough ride it has been)

This has led me to think that the real high stresses on the joints of a young (or old!) arm are the “dynamic” forces – forces that are in reaction to the motion and intertia of the arm itself, rather than the “static” forces – the forces that the contractions of the muscles of the arm exert on the joints. I think that a lot of mechanics gurus and even top arm docs don’t have a solid understanding of solid body dynamics and they miss this point.

Furthermore, it’s logical that the heavier the ball you are throwing, the lower the arm speed, and thus the lower the dynamic forces on the joint. So if I’m right, throwing a heavier ball would lead to fewer injuries and throwing underweight balls would lead to more injuries.

What do you think?

I should point out that I think throwing “all arm” is a flaw and I’m not advocating it at all. I don’t think it’s dangerous, though, just ineffective.

In general, agree with this.

This is an incredibly insightful and well-thought-out post.

[quote=“bbrages”]The only thing is… compared to kid pitchers his age that I’ve seen, he puts his whole body into it very well. His arm really is “just along for the ride”… (but what a rough ride it has been)

This has led me to think that the real high stresses on the joints of a young (or old!) arm are the “dynamic” forces – forces that are in reaction to the motion and intertia of the arm itself, rather than the “static” forces – the forces that the contractions of the muscles of the arm exert on the joints. I think that a lot of mechanics gurus and even top arm docs don’t have a solid understanding of solid body dynamics and they miss this point.[/quote]

Very much yes. Just because the “arm is along for the ride” doesn’t mean that the arm is not undergoing serious compression and distraction forces about the shoulder and elbow. In fact, the more “efficient” the mechanics, the more stress on the joints! Now this isn’t necessarily a negative, but it’s just basic physics - you don’t get something for nothing.

[quote]Furthermore, it’s logical that the heavier the ball you are throwing, the lower the arm speed, and thus the lower the dynamic forces on the joint. So if I’m right, throwing a heavier ball would lead to fewer injuries and throwing underweight balls would lead to more injuries.

What do you think?[/quote]

Interesting theory. At Wolforth’s Coaches’ Convention in December 2012, I presented data from our biomechanics lab that showed pronation angular velocity decreased as the weight of the implement decreased - that is to say, it varied directly and linearly with the implement’s weight.

So, in theory, a heavier baseball is safer on the arm. However, there is likely additional stress at MER with a heavier baseball (inertial mass goes up) than there is with a regulation baseball - the big tradeoff is that there is less stress through the acceleration phase and recovery phase. Heavier implements may increase the TOTAL load on the arm, but the PEAK load through acceleration is reduced. The inverse is true with underload baseballs (lower stress at MER, massively increased stress through acceleration and recovery).

Great explanation.

When I throw the 4 ou ball it seems to bother my shoulder, whereas the 6 ou ball feels about right.

Of course the 4 ou ball goes about 10mph faster though (so that probably explains it).