I've been able to hold a tuck planche for long time now and feel fairly comfortable holding it.
I put a mirror to the side to observe my development of advanced tuck planche. I'm aiming for the lower back to become a straight line with the rest of the body.
I can lift the lower back for a couple of 3-4 seconds but after that it goes back to the rounded back shape.
I was wondering if that is happening because of inadequate lower back strength. Anyone has gone through this as well? If that is the problem, what should I work on?