Hanging Pike

How to do it

Hang from a chin-up bar with your legs and feet together using an overhand grip (palms facing away from you) that is slightly wider than shoulder width. Tip: You may use wrist wraps in order to facilitate holding on to the bar.
Now bend your knees at a 90 degree angle and bring the upper legs forward so that the calves are perpendicular to the floor while the thighs remain parallel to it. This will be your starting position.
Pull your legs up as you exhale until you almost touch your shins with the bar above you. Tip: Try to straighten your legs as much as possible while at the top.
Lower your legs as slowly as possible until you reach the starting position. Tip: Avoid swinging and using momentum at all times.
Repeat for the recommended amount of repetitions.

What muscles does the Hanging Pike work?: Mainly the abs.
What equipment do I need?: Nothing but your bodyweight.
Is it good for beginners?: It is rated expert level, so learn simpler versions first.
How do I track progress on it?: Log each set and beat the weight or reps from last time. Liftrung shows your last set beside the next one and estimates your one-rep max from your sets.

Exercise descriptions: free-exercise-db, public domain.