Getting a flat stomach is not easy; it takes time, patience and dedication. However, if you target your stomach with appropriate exercises, you should see a noticeable difference in a matter of weeks. Crunches alone will not give you a flat stomach: You must incorporate cardiovascular exercise as well as modify your diet to achieve a flat stomach.
Lie on the floor, bring your knees up, keeping your feet flat on the floor. Keep your hands by your sides or cross them over your chest. Keep your back straight and pull your stomach muscles in while doing these crunches. Breathe slowly, and lift your shoulders up and forward. You don't have to pull yourself all the way up. Aim to bring yourself up 30 percent of the way. This is the correct way to to do an effective crunch, according to the U.S. Navy website. Perform three sets of 10 repetitions, taking a 30-second rest in between each set.
Perform crunches with your legs raised. These crunches target the lower stomach muscles. Lie on your back; instead of raising your knees, bring your legs up. Cross your feet and make sure your legs are straight, if straightening your legs is too difficult, you can bend them slightly. Put your hands by your ears, and pull in your stomach muscles. Again, raise your shoulders off the floor only 30 percent of the way. Breathe slowly and do each crunch as slowly as you can. Do three sets of 10 repetitions and rest in between each set.
Do crunches that will target your internal and external oblique muscles. These are the muscles that can help you to reduce the size of your waist and are located along the sides of your torso. Lie on the floor in the same starting position as the traditional crunch, with your knees raised. Instead of bringing your shoulders up and forward, come up and bring your right elbow to right knee; you can put your hands behind your head or leave them by your sides. Do the same on the left side, and perform three sets of 10 repetitions.
Do cardiovascular exercises. Crunches will help to tone and tighten the muscles in your stomach, but you need to do cardiovascular exercises to burn the fat. Your six-pack abs will not show through unless you burn the fat that covers the muscle. Therefore, you will need to carry out at least 30 minutes of cardiovascular exercise -- running, cycling or swimming -- at least five times a week. Depending on the amount of weight you need to lose, you might need to engage in more than 150 minutes of cardio exercise weekly to drop the pounds.