answer:Planks-elbows underneath the shoulders, body rigid with neck inline with spine, pull your navel toward your back. Basically hold position and use your ab and back muscles as opposing forces. 60 sec. on/off for 3 sets will kill you. Do 30 sec. with better form if you can’t. Squats, dips, pushups and pull ups are going to be your core exercises as far as compound movements go. And if you want to hurt, done correctly, sissy squats (they make you whimper like a bitch) effectively work the whole upper leg.