During both the Hollow body and arch body holds, I find myself losing position long before I really feel fatigued. In hollow body my lower back will start creeping up from the floor and there's nothing I can do to stop it. Likewise in arch body I just start going flat, and it feels like I should be able to fight it but I can't. This especially occurs when I'm trying to 'stretch' my body during the holds, which I understand is the right way to do approach it. I mention them together because it feels like the same muscles are giving out even though they are opposite motions. I suspect my trans abs are being inhibited somehow, but that's just a novice's guess at the problem, and I don't know how to address it regardless.
Any help is much appreciated.