crunch or sit-ups, try planking for 2-minute intervals. Pull in your abs while you are planking and you will definitely feel it after 3 reps.
Do the bicycle to target other ab muscles
(crunches work only the rectus abdominus, aka your six-pack): Lie with your hands behind your head; alternate touching each elbow to the opposite knee.
Don’t neglect your midback muscles (the lats).
They work with your core to help you stand straighter, minimizing your pooch. Try Lat Rows: Bend at the waist and hold a dumbbell in each hand; bend elbows and pull weights up until elbows are level with the torso.
To really challenge your abs, crank out