Alternate Heel Touchers

How to do it

Lie on the floor with the knees bent and the feet on the floor around 18-24 inches apart. Your arms should be extended by your side. This will be your starting position.
Crunch over your torso forward and up about 3-4 inches to the right side and touch your right heel as you hold the contraction for a second. Exhale while performing this movement.
Now go back slowly to the starting position as you inhale.
Now crunch over your torso forward and up around 3-4 inches to the left side and touch your left heel as you hold the contraction for a second. Exhale while performing this movement and then go back to the starting position as you inhale. Now that both heels have been touched, that is considered 1 repetition.
Continue alternating sides in this manner until all prescribed repetitions are done.

What muscles does the Alternate Heel Touchers work?: Mainly the abs.
What equipment do I need?: Nothing but your bodyweight.
Is it good for beginners?: Yes, it is rated beginner level.
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.