I have been working on this movement for months now. As you can see from this video I have really bad Thoracic mobility. When I rock I hit a flat spot and takes all my rocking away. I tried to do assisted sit-ups as I read somewhere that can help. Any suggestions on how to improve the flat spot. I'm able to do 60 reps for a 2 to 3 sets after that it becomes a challenge to hit 60. Not sure if it is just still muscle adaptation but this would be the longest I have experienced by a factor of 3 or 4. Seems like I'm missing some mobility or technique.
Thanks in advance,
Cory