For this exercise, you need a mat or a soft clean surface to lie on.
Start by lying face down on the floor, legs straight and arms extended, palms down.
Contract your abdominal muscles and keep your head and neck aligned with your spine. Squeeze your shoulder blades together, then lift your arms and torso until your chest just clears the floor. Hold for 2 to 3 seconds. Slowly lower to the start position. Do 8 to 10 repetitions.
As you become stronger you may hold the lift longer -- 5 to 10 seconds. When you are comfortable with the exercise, gradually increase the number of repetitions. When you can do 12 or more repetitions, increase the holding time to bring you back to the 8-to-10-repetition target range.