Doing sit-ups or crunches can strengthen your abdominal muscles. But you have to do them correctly to achieve good results.

Well-toned abdominal muscles, which run from the lower part of the rib cage down to the pubic bone, keep your spine aligned and protect internal organs. They also transfer force between your upper and lower body more efficiently so you can easily perform everyday movements, such as bending, lifting, squatting, walking and reaching.

To tone your abs effectively, follow these simple rules

Rule 1
To set up your sit-up properly, lie on your back with your knees bent and your feet flat on the floor close to your hips. Keep the small of your back flat on the floor This will help you engage your abs instead of your hip-flexor muscles.

With your hands resting lightly on the side of your head, exhale, tighten your abs, then lift your head, neck and shoulders off the ground.

DO NOT put your hands behind your head to pull yourself up, as this may damage your neck and spinal chord.

Rule 2

As you lift your head, neck and torso, make your abs do the work, not your neck and lower back. Go slowly and with control. Sit up only high enough for your shoulders to clear the floor. Avoid rushing and using your body's weight to complete the move. Control is everything.

Rule 3

Avoid doing too much too soon. No matter what type of abdominal exercise you do, quality, rather than quantity, counts. Ten to 20 safe sit-ups performed with good form are equal to 100 fast and sloppy ones.

Rule 4

Also exercise the lower abdominal muscles. Lying on your back with knees bent. Tighten the abdominal muscles, bring one knee towards the chest, Keep it there. Hold the back and pelvis stable by keeping the abdominals contracted, bring the other knee up to meet the first one, then lower the first one, then the second leg. Relax the abdominals and repeat.