Should I be able to press my lower back into the mat when laying all the way out?

Question

I'm a 25 year old female, personal trainer and I live in the south, so hot and humid for the most part.  

I'm wondering if I'm supposed to be able to flatten my back on the mat when lying down, limbs long.  If so, what can I do to work towards that? I've tried upping my back workouts and core workouts but I can't seem to flatten my back unless my feet are on the floor. Should I be able to do that or not?

Answer 1

The spine has its convex and concave curvatures and it should not be interferred with during exercise.

So, in supine position, try to maintain curvature of the spine. No need to press the lower spine.