Basic crunches
Lie on your back to do basic crunches. Pull up and bend your knees, placing your feet flat on the floor. Place your hands behind your head, with the fingers interlaced. Slowly lift your upper body three to four inches toward the ceiling, engaging your abdominal muscles to make the lift. Hold the position for one to two seconds and lower slowly.
Start with two to three sets of 10 to 15 crunches, increasing the number in each set and then number of sets as you progress.
Bicycle crunches
Start from the same position you use for basic crunches to do bicycle crunches. As you lift your upper body, twist it so that your right elbow points to your left knee. Simultaneously, lift your left knee and pull it toward your upper body. Lower, and repeat the crunch, substituting the left elbow for the right, and the right knee for the left.
Start with two to three sets of 10 to 15 bicycle crunches, increasing the number in each set and then number of sets as you progress.
Plank
Lie face down on the floor to do a plank. Support your upper body up on your forearms, holding your forearms underneath your shoulders, parallel to each other and in line with your body. Lift your legs and support them on your toes. Straighten your back and hips so that your body is in a straight line from your heels to your neck. Hold the position without moving.
Start with two to three planks, holding each for 20 to 30 seconds. As you progress, increase the duration of the plank.
Reverse Exercise Ball Crunches
Lie face down on an exercise ball, with the ball under your hips and your feet on the floor, supported on your toes. Keep your back straight and place your hands behind your head, with the fingers interlaced. Raise your upper body up three to four inches, hold for one to two seconds and then lower to the original position.
Start with two to three sets of 10 to 15 reverse crunches, increasing the number in each set and then number of sets as you progress.