Warming Up Middle Body Lie flat on your back on the floor, and bring your knees up to about 90 degrees. Then, with your hands positioned either behind your head (do not pull on your neck as you come up) or reaching forward, slowly lift your upper body using your abdominal muscles. Keep your back rounded throughout the exercise, as it is very important not to arch the back. To do this you should concentrate on pushing your lower back into the floor. You can vary the above exercise by reaching forward to the right or left of your knees, as this will use slightly different muscles. You can alternate from side to side or do five on one side followed by five on the other, or whatever you can comfortably manage. For your lower abdominal region, bring your feet off the floor, place your hands on either side of your head, crossing the ankles. Using only the abdominal muscles bring your knees toward the chest and elbows and shoulders toward the knees.