Bicycle crunches help build strength and tone your core. They focus on the sides of your core, also known as your obliques.

1. Lie on your back with your hands behind your head and your legs lifted off the ground.
2. Bring your right elbow towards your left knee while extending your right leg.
3. Switch sides, bringing your left elbow towards your right knee while extending your left leg.
4. Continue alternating sides in a pedaling motion.