Two long straps
Your rectus abdominis is two long, flat straps of muscle, one on each side of a line down the middle of your belly.
They run from the bottom of your ribs down to the front of your hip bones.
Rectus means straight, and abdominis means belly. So it's the 'straight belly muscle.'
Why it looks like a six-pack
Bands of tough tendon cross the muscle, sideways. They split it into boxes, usually six or eight. A tough stripe runs down the middle too.
Everybody has these boxes, whether you can see the lines or not. On most people you can't, and that's totally normal.
Bodies come in all shapes, and belly muscles do their jobs great in every one of them.
Sit up, bend and stand tall
Try it: lie on your back with your knees bent. Put a hand on your belly and lift your head and shoulders a little. Feel your belly get firm?
Your belly muscles curl you forward. You use them to sit up in bed, bend down to tie your shoes and roll over.
Your belly muscles and back muscles also work together to hold your middle steady. People call this team your core. It helps you stand tall, balance, run and throw without wobbling.
Try it: stand on one foot. Feel your belly tighten a little to keep you balanced?
A shield that helps you cough
Your lungs and heart have ribs around them. But there are no bones in front of your belly. Instead, your belly muscles and your side muscles make a strong, stretchy wall that holds your insides in place and helps protect them.
That wall can squeeze, too. Try it: put your hand on your belly and cough. Feel a quick squeeze?
Your belly muscles push air out fast when you cough, sneeze, shout or blow out birthday candles.
Laughing really hard can make your belly feel tired. That's because your belly muscles squeeze with every 'ha!'