What is the most efficient exercise to firm the abs?

This season's hottest belly-baring bathing suits call for great abs. Fitness expert Martha Coopersmith of The Bodysmith Co. in New York recommends these three easy exercises to help strengthen, tone and flatten the abdominal area. Do the exercises at least twice a week; if you can do them more often, that's great -- they're safe enough to do every day. Don't expect instantaneous results, but with consistent exercise and a proper low-fat diet, you could see results in as little as two weeks. Lie on your back with your knees bent and your legs 12 inches apart. Put your hands on your abdominals so that you focus on using only those muscles. Lift your bent right leg up to the ceiling, then your left. Lower your right leg, then your left. Repeat, but this time pull your abdominals in even more when you lift the second leg up. Continue the exercise by lowering the right leg, then the left,to starting position. Keep your abdominals as tight as possible. Do three sets of 10reps, alternating the leg that goes first. Lie on your back with your knees bent and feet off the floor at a 90-degree angle. Keep your ankles crossed and your hands behind your head. Contract your abdominals and try to "levitate" your hips off the floor. (You should be concentrating on the contraction, not on raising your hips off the floor.) Your hips should lift only about an inch. Do as many as you can correctly, working up to 50. Lie on your back with your knees bent and your hands behind your head. Lift your upper body up to contract your abdominals. (This may only be two or three inches when you begin doing this exercise.) Return to starting position. Make sure that you feel the weight of your head in your hands. Exhale when you are curling up and inhale on the way down. Do as many as you can correctly, working up to 50.

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