You can do this exercise either at the gym or at home. If you prefer to do them at home, you may be more comfortable performing this exercise on a yoga mat, towel or any other soft surface you can put between you and the floor.

This exercise works your rectus abdominis muscles, which are the major muscle group in your core and the muscles responsible for the six-pack look. Bicycles also target your oblique muscles, which are located on the sides of your abdomen and control lateral movement.c 

1. Lie flat on the floor with your hands behind your head to support your neck, but don't interlock your fingers.
2. Bend your hips and your knees so that your thighs are perpendicular to the floor and your shins are parallel to the floor.
3. Lift your head and shoulders off the ground to engage your abs, making sure that your neck doesn't collapse towards your chest. Sometimes it helps to imagine keeping an apple between your neck and chest.
4. Keeping your good form, rotate your torso so that your right elbow moves toward your left knee. At the same time, bring your left knee in towards your chest and extend your right leg so that it is parallel to the floor without touching.
5. Rotate your torso to the other side so that your left elbow moves toward your right knee. At the same time, bend your right knee into your chest and straighten your left leg so that it is parallel to the ground without touching.
6. This counts as one rep. Repeat 15-20 times.

Tip: Keep the momentum slow so that you have time to perform each rep with proper form.

Tip: Make sure you lift your shoulder blades off the ground so that you are getting the full ab-working benefits.

Variation: At the point of the exercise where one leg is extended and you are crunched inward, hold this position for a count of five. Switch sides and hold for another five seconds. Continue with your set as normal.