a crunch is when you only go half way up and a sit up is when you go all the way up, i think sit ups are harder to do cause you go all the way up, crunches work good for me i do 50 a night, i'm tring to get my stomach flatter. it hasn't shown much improvement though. well i'll see ya later, would you e-mail me or something? Lizzy_87@hotmail.com or i have msn messenger. see ya later i hope i helped amanda