Bicycle crunches are a popular abdominal exercise that targets the core muscles, particularly the rectus abdominis and obliques. To perform this exercise, lie on your back with your hands behind your head and your legs raised at a 90-degree angle. As you lift your shoulders off the ground, bring your right elbow towards your left knee while straightening your right leg. Then, switch sides by bringing your left elbow towards your right knee and straightening your left leg. This motion mimics pedaling a bicycle, hence the name. Aim for controlled movements to maximize effectiveness and reduce the risk of injury.