Normally I do today’s exercise on the rings, but it’s also fine doing it on a bar or a branch to train the abdominals, strengthen and stretch the shoulders and increase also the coordination skills.
I hold myself on a bar with closed legs. They should stay closed during the whole exercise. Now I start lifting my knees upwards to my chest and slip with my feet through my arms by rolling my upper body backwards. Then I lower my legs down backwards until my body is as extended as possible. Of course the exercise is not over yet, because now I must go the whole way back until I’m in the starting position again.