5. Elbow-to-Knee Crunches
Lie on your back, bend your knees 90 degrees and lift your legs up. Place your hands behind your head and lift your shoulders off the floor. Then twist your upper body to the right as you pull your right knee in to meet your right elbow. At the same time straighten your left leg. Then switch directions and touch your left elbow to your left knee, alternate sides and repeat 25 times.
