Doing repeated crunches and abdominal exercise will help you to improve your abdominal strength and develop ‘six-pack Abs’. HOWEVER if there is a dense layer of fat over your abdominal area you will not be able to visually see the results of all of your abdominal work. To tone your stomach muscles you must first reduce your body fat by exercising well and eating right. Once you have sufficiently reduced your body fat levels you will be able to enjoy your ‘six pack abs’. But just crunches alone will not be enough to bring out your washboard body. Besides keeping your abs/core properly engaged throughout a regular strength training workout will give you a better abdominal training session than just performing loads of sit ups.