Move 1: Bird-Dog
To work your six-pack area and back, remain on all fours and tighten your abdominal muscles, keeping your spine and neck in a neutral position; you should be looking at the floor (top illustration). Slowly extend your left leg behind you while reaching your right arm forward (bottom illustration). Keep your hips and shoulders square and make sure your lower back doesn’t arch. Hold for five seconds. Slowly return to the starting position and do the move on the opposite side. Complete 5 to 10 repetitions on each side.