With a grip well outside shoulder width, hang freely from an overhead bar as you would doing a pull-up. This will be your starting position.
Instead of pulling your knees directly up, go in a counter-clockwise direction with your knees holding in 90 degree position.
Continue in a circular motion until you are back to the center, reaching full leg extension.
Complete for the designated number of reps in the same counter-clockwise motion. Because of the asymmetrical motion you'll repeat the move for the same number of reps going in a clockwise direction as well.