You know that head forward, rounded shoulders posture that you get from reading your phone or sitting at your computer? That’s the same body position as a crunch, says Wismer.
“Because most people do a crunch by pulling up on the head, not by using the abs, all this move does is reinforce that bad posture.”
Until you are strong enough to do a crunch using your abs and not pulling, try to use your legs instead. Lying on your back, lift your legs to the sky, and lower them part way down – until you feel your core really tighten – then lift them back up.
Also: Try these eating tricks to get a flat belly.