Only you can put a limit on what you achieve. You are the one that can hold yourself back or push your body to its potential in this 30-day challenge. I understand that there can be health problems that may prevent some from performing every exercise, but there are always replacement exercises that you can do to make up for what it is that you physically cannot achieve. This website below gives about 100 ab exercises and when you click on the name of the exercise it will transfer you to a page that will show you pictures and have an explanation of the exercise. I highly suggest to check it out for more exercises to perform then just the few I gave you last post.