Tightening the internal abdominals is the key to achieving a streamlined tummy on the outside. One of the best ways to do this is with the Plank, a tummy-toning exercise that rewards reps with a stronger torso and a flatter tum. Lie on a soft surface on your stomach and place your elbows into the side of your body with the arms bent. Lift up on to your knees and keep the elbows under the shoulders and the bottom below the shoulders. Hold your tummy in tight and hold the position for 5-10 breaths. To advance this exercise repeat as above but come up onto your toes. If you feel your back start to arch downwards, drop back to your knees and continue holding.