Bill Sands and collaborators did a study for Ron Brant, Men’s Senior National Team Director for USA Gymnastics, at the Colorado Olympic Training Center.
They analyzed (now National Champion) Alex Artemev who had already done quadruple twist on floor. As it is for Nastia Liukin, this is an important target skill for Artemev.
The research did not come up with any need-to-know conclusions. But the simultaneous video / computer model analysis tool is certainly cool. See for yourself: The Triple- and Quadruple-Twist:: A Case Study
Here is a screen shot to give you an idea how it looks:
Gymnastics Coaching.com 