[Lie on your back and raise your legs] mainly exercises the abdominal muscles. Lie on your back with your hands clasped behind your head. Bend your legs and stack your calves together. Use the strength of your abdominal muscles to lift your knees toward your chest, and at the same time roll up your upper body until your thighs and abdomen form a 90-degree angle. At the top of the movement, your hips are off the floor. Then slowly return to the starting position. Do 4 sets of 15-20 reps every other day. Be careful not to use your hands to pull your head forward.
