But by thinking about how my muscles work, I can't figure out how I can raise my arm like this, and not activate the shoulder. Because muscles only contract, I can't figure out how the muscles below my arm can raise my arm. When holding weight, I can activate my lat for more support, but there is no doubt, when I try it, that my shoulder has to activate..
Both the standard body use of Ki Aikido and the Pilates teaching "go down to go up" teach this body usage.
The model I learned via aikido is to simply point at something the way you would when, well, when pointing at something
. The ki test is to have your arm seized and simply point at something. The visualization or intent is that the shoulder and arm are still and relaxed and the finger simply extends and rises. The aikido model posits the triceps as doing the work.
The Pilates model is that to learn this, you first drop your shoulders and then you simple allow your arms to raise. The Pilates perspective is you are enlisting primarily the latissimus dorsi.
Using both models, I believe it is initiating gross movement w/ the lats and secondarily maintaining extension via the triceps.
In and of itself this is not what I'd call "internal training" but it is certainly what I'd call "best use" body mechanics. And it is a very good way of beginning to understand the connection between intent and efficient body usage.
(note: when talking about dropping shoulders: the commonest model is to feel like you are pushing them down from above. If you know how to isolate the tiny muscles at the lowest part of the scapula, you engage them and literally pull the shoulders down into the core - I can teach this IRL via touch the way it was taught to me, but cannot possibly do it w/ words or pictures because I think for most of us the muscle itself must be touched for the person to go OH, that...that can move?)