how do bicycle?
Do the Bicycle Crunch: 1  Lie flat on the floor with your lower back pressed to the ground and contract your core muscles. 2  With your hands gently holding your head, lift your knees to about a 45-degree angle. 3  Slowly, at first, go through a bicycle pedal motion.  Alternately touching your elbows to the opposite knees as you twist back and forth.