Lift your feet off the floor, with your knees at a 90 degree angle. Squeeze your abdominal muscles tight and lift your upper body till your shoulder blades come off the floor, while simultaneously lifting your hips off the floor. Crunch the tummy hard and slowly lower. Before you release, lift up again.

Do 16 reps. Next, let the hips keep doing the same lifting movement while you change the upper body movement. As you come up bring your right shoulder towards the left knee. Lower and then bring the left shoulder to the right knee. Keep alternating sides and do 16 reps.

Crunches work your upper abdominals, lower abdominals and the oblique abdominals that criss-cross your tummy.