The crunch is a classic core exercise. It specifically trains your abdominal muscles, which are part of your core. Your core consists not only of your abs. It also includes your oblique muscles on the sides of your trunk, as well as the muscles in your pelvis, lower back, and hips.

Can you do crunches in bed?

Reverse crunches

Lie on your back with your hands by your side, palms down. Keeping your legs straight, use your abs to lift your legs toward your face until your toes touch the headboard. Slowly lower your legs back to the bed, engaging your abdominals. Don't let your lower back arch up off the mattress.

Do crunches give flat stomach?

The truth is, targeted fat loss — also known as spot reduction — is not possible, no matter how many crunches you do or products you buy. The only way you can lose fat from your belly is to lose fat from your entire body. Situps and crunches simply won't do this for you, even though I'm sure you've heard otherwise.