Gorilla Chin/Crunch

Hang from a chin-up bar using an underhand grip (palms facing you) that is slightly wider than shoulder width. Now bend your knees at a 90 degree angle so that the calves are parallel to the floor while the thighs remain perpendicular to it. As you exhale, pull yourself up while crunching your knees up at the same time until your knees are at chest level.