What muscles are being worked with a plank?

Your abs are being worked out,it's one of the best work-outs for abs!So get started!I started out doing planks for 30 seconds once a day and I am working my way up!Also if you feel your abs burning then that means your abs are responding to the work-out naturally.Remember if you breath it's not that bad,so breath!Always keep your back and hips straight.So there you go I hope I helped you out!!!