Circuit 3, Exercise 4: Bicycle Crunch Lie flat on the floor with your lower back pressed to the ground. With your hands behind your head, bring your knees toward your chest and lift your upper back until your shoulder blades off the mat. Be sure not to pull on your neck. Straighten your right leg out to about a 45-degree angle to the ground while turning your upper body to the left, bringing your right elbow toward the left knee. Make sure your rib cage is moving and not just your elbows. Switch sides, and do the same motion on the other side to complete one rep. Complete 15 reps. Image Source: POPSUGAR Photography