Needs more eyes

[jfitch12]

Usually the glove arm is externally rotating as it comes down (turning palm up), though it may not turn very much.

You will hear a lot of people say that they don't address glove swim or that it is just a "symptom" of other things, and I think that is probably right. If you imagine a line from the back shoulder through the front, the glove will usually be within 6 or 8 inches of the plane created by that line and the athlete's belly button. So when people say that they see a lot of "swim," they are really just seeing (1) the front arm extending out (rather than being tucked tight to the body) and (2) the trunk being more closed than open (i.e. turned more towards first base than home for a righty). The amount of "glove swim" usually just tells you about the shoulder line--nothing more. "Glove swim" is not an independent issue with the front arm.

That is not to say that you can't change the shoulder line by focusing on the glove. Sometimes trying to keep the glove pointed to the catcher is the easiest way to keep the shoulders pointed that way too. The body moves proximal to distal, but a lot of athletes are able to control their extremities better than their core, so they can make mechanical changes to their middle by focusing on the extremities. That has been my daughter's experience with a lot of mechanical issues at least.

 

[ArmWhip]

Is glove arm swim rotation of the arm, internal rotation?

Glove arm swim always concerns me because it is a symptom of, or a precursor to, rotating the shoulders (closing) as a way of adding 'force' to the throwing arm. Ideally you want balanced arm adduction: as the throwing arm comes down the back side the glove arm pulls down and in also, although not as forcefully.

 

[Fluid Fastpitch]

Keep in mind that good reciprocal scap engagement (the "Flex" position from "Bow, Flex, Bow" you'll hear thrown about here) can look like glove swim, especially for girls with more flexible shoulders. If there is no external rotation of the glove hand, there probably isn't scap engagement. So some amount of 'glove swim' is normal, healthy, and expected during a pitch. And I would add, if there's no scap engagement, there's probably not a strong adduction, and the core is probably not well engaged either.
But yes, shoulder angle throughout the pitch should be considered. It's just not necessarily related to how far outside the body the glove is getting.