Reverse Crunch - this might be another variation regarding crunch. There are countless variants to this workout as it works the abs so well. Each variation works an unusual the main abs, which means you have a well curved six pack. This is actually the whole point of these six pack abs exercises. Like all crunch exercises, this is started by laying flat on the floor. After this you raise feet from the ground in a kneeling position. Next, bring your knees into your chest.