That's an animation I've been thinking about for a very long time, but I never dared to try and animate it, thinking I'm not good enough to do it properly. Eventually I decided to do it and see what happens. And it's not so bad after all.
Animation length is about 8 seconds of doubleframes in 24 fps.
I would have added a colored figure with all the inbetweens if I had time, but I don't.
(read this post for explanation why http://injured-ninja.newg rounds.com/news/post/2737 33 )