Quick Tip: If you don't have a lot of time, but still want to train your abs, try 3-5 second isometric contraction crunch squeezes. You can do them while sitting, driving, etc. Do about 5-10 contracts/holds in one session 1 or 2 X every other day. Make sure to exhale while contracting/squeezing and take a deep breath before going into your next 3-5 second squeeze. When I say contract, bare down as you would when pushing to urinate - This will help you to feel what you should be feeling. You should feel tightening of the ab muscles and with 5-10 squeezes, you'll feel the muscles burning soon enough.