I've been looking at this screenshot of my Jump back and comparing it with shots from other jump backs on you tube. this is the point where my feet brush the top of the mat. If the mats not sweaty then it will stop me dead, pull up the mat or I'll have to add an extra little hop to get through.
If I look closely I notice that I'm curled up tightly into a ball, my back is rounded and my knees up high and close to my chest. My shoulders are forward of my hips and my legs are crossed at the ankle, the right a little higher up the shin. And are my elbows pointing outwards?
Now if I look at Sharath the posture is completely different. For one thing he looks relaxed, his whole jump back appears almost effortless. This screenshot is of the same moment in the jump back, just before the feet pass the arms and go on through. His feet are higher, obviously, crossed at the ankle but closer to his backside. However his knees aren't as close to his chest as mine. His back is straighter,perhaps because of this and his whole posture less scrunched up
Similar postures from Shelly and Rob Lucas below.
However, if we look at john Scott his knees appear higher and closer to his chest like mine, but again, his back appears longer. If the above four where on a horse we might say they sit tall in the saddle
The final two shots I looked at, Derek and Idoru are in many ways closer to mine in that they appear more rounded, tighter and yet they're clearing the mat completely and I'm not.
One thing I noticed though in all these shots are the feet. They all seem closer to their bottoms at the expense of the knees being closer to the chest and I think this might be where my difficulty lies. I've tried hard to bring my knees up higher and close to my chest and that kind of locks the feet. it's hard to pull them in closer when your focused on your knees. But if you relax your knees a little and drop back slightly it becomes easier to pull the feet in.
So try this. Lift your knees up high to your chest as you lift up with your arms but then relax the knees a little as you pull your feet in closer to your butt which begins the pivoting motion taking your hips back your shoulders forward and hopefully your feet through. This is what I'm working on at the moment, tricky getting the coordination right but think I might be on to something.
That and trying to sit taller in the saddle.
Ashtanga Yoga Primary Series DVD w/R. Sharath
Yoga - Ashtanga - The Primary Series John Scott
(youtube video seems to have disappeared)