Sherri, I know I have a weak thoracic and when I try these exercises my lower back hurts. How can I overcome that? I don’t seem to be able to keep my abs pulled I enough while in prone.

Hi Margaret T, I am so sorry about the low back discomfort.  Try placing a fairly thick 12"x12" throw pillow under your chest and abdomen.  Place it so that your pubic bone is floating or barely touching the floor and not actually on the pillow.  What it will do is create a sort of "seesaw" effect under your sternum which tilts your lower ribs toward your pelvis and "helps" you lift your chest up a little higher.   Try the pillow in different positions under your body moving it toward your head and toward your feet and then try the thoracic chest lift and see which angle helps relieve your low back the most.   Let me know if that helps!  

That was brilliant. Now I know how to target the upper, mid and lower thoracic using by changing the arm position. So useful.