I've been critiqued a few times for not arching my back enough during squats. Often I do it with a flat back or a very minor arch. I'm told that the way to correct it is to stick my ass out more when i descend, but I can't do this even with little/no weights.
I've been doing squats for about a year now and it doesn't seem to be getting any better (though thankfully not getting worse either).
What do I need to do to improve my form on this? I've tried doing some stretches, particularly hamstring stretches because I thought that was the problem.
Has anyone managed to correct this problem? Thanks, guys!