Ready to work those abs? In this Fit Life, I’m going to show you how to do a stability ball crunch. You might be tired of your old ab workout, or maybe just need something new and different to add to your routine. Â Take notice that this exercise is suppose to really work the abs, not the hip flexors. Â If your lower body is moving throughout, then you need to re-evaluate your positioning. Â If you are wanting to work your hip flexors, then this video will not help you!