Yes you can. With what we know about functional anatomy doing crunches is like saying that preacher curls are functional. Its rediculous for anybody to still be doing crunches when the function of the core is stability and force transference Not to mention in the current postural crisis caused by the technology we now have, crunches only overemphasize upper cross syndrome. It flies in the face of current exercise science knowledge to do crunches.
There is a movement issue here that nobody is addressing. The rectus abdominus does not function by itself and should not be trained in isolation. The only time any type of isolation should be used is if there is a compensation due to a weakness in a movement pattern then go back to a functional integration movement pattern and train correctly.