Alternate working your back and abdominal muscles with this simple routine. You can easily perform both of these moves at the end of your weight- or cardio-strengthening program to keep your core muscles strong and flexible. You will gradually be able to hold each position longer, but remember that patience and consistency will yield far better results than forcing your body to hold new positions too long, too soon.
— Karen Voight
1 To strengthen your back extensor muscles, lie face down on a padded surface or a mat. Stretch your legs behind you with the tops of your feet on the floor, hip-width apart. Keep your inner ankles parallel to each other and your knees straight. Place your hands in front of you, flat on the floor, with your forearms parallel to each other and your elbows directly below your shoulders. Press down against your forearms as you raise your chest, shoulders and head away from the floor. Engage your back muscles and slide your shoulder blades down away from your ears as you elongate the front of your torso. Hold for 8 to 12 seconds.
2 To strengthen your abdominal and upper body muscles, lie face down on a padded surface or a mat in the same position as at left. This time, press down into your forearms as you lift your waist, hips and thighs off the floor. Engage your abdominals to prevent your lower back from overarching. Hold for 8 to 12 seconds.