1. Lie flat on your back, preferably on a comfortable surface, and place your fingertips lightly behind your ears
2. To get into the starting position, contract your abdominal muscles to bring your shoulder blades off the ground and your legs off the ground with a slight bend at the knee
3. In a pedaling motion, bring one leg in towards your body while you tilt the opposing side of your upper body allowing your elbow to close in towards the bent knee
4. Extend your leg back outwards as you repeat on the opposing side
5. Repeat this motion, using a fluid, continuous motion for the specified amount of reps or time
The primary muscles used in Bicycle Crunches are the Abs. The secondary muscles used are the Obliques.