Hi! I hope this is the right place/way to get some clarity.
I went through Fundamentals last year and since then I've been working my way through Foundations 1 (very slowly!) and the mobility series, and I just started Movement. I love GB 
and am feeling generally more connected and mobile since starting.
Two questions:
the six quadruped warm ups in Movement, which I remember from Fundamentals are great (hard but fun!). How long do I do them? The videos are about 15 seconds each but I'm assuming that's just for demonstration.
The opening movement in Thoracic Bridge mobility video, rocking table: this really hurts my lower back! I can't figure out why, and I've tried little tweaks (more pushing through hands, through feet, rocking forward more/less). This is often a weak area for me, which is part of why Thoracic Bridge is so important for me. Any ideas? (Is this usual? Should I send in a video for review?)