Ever wonder which is a better workout for your abs? Paul Becker, owner and operator of Trulyhuge.com,  says traditional sit-ups emphasize sitting up rather than merely pulling your sternum down to meet your pelvis. The psoas muscles run from the lower back to the front of the thighs. This muscle action is to pull the thighs closer to the torso. This action is the major component of sitting up.  Because of this, when you are doing sit ups your psoas muscles are the primary muscles being engaged and not your abdominal exercises.

So, sit-ups are a pretty useless exercise if you want to get your abs in shape. Instead, use crunches, because they directly work your abs. *But remember, no amount of crunches or ab work will produce a visible six pack unless you burn any excess belly fat that is covering up those abs muscles.  Of course, that can be accomplished through diet and exercise.

For more information on the difference between the two exercises, read this.