The supine cross-connect has been one of my favorite moves that I’ve been using lately (kudos to Bill Hartman for this one).
I got asked about the biomechanics on this move, and we deep-dived into it on this video.
supine cross-connect components
The big key that this move is driving is rotation. The rotation occurs towards the flexed leg, and each component within it drives these changes.
The progressive hip flexion drives sacral rotation ipsilaterally, with the extended leg driving internal rotation. The bias overall in the lower body is toward internal rotation, but the body is still turning towards the front leg.
The contralateral reach drives rotation towards the flexed leg, again, encouraging posterior expansion on the flexed hip side.
The combination of all these factors makes it a pretty awesome move!