I had one done a while back. Basically they check your limitations as to how far you can walk, how much you can lift, how much you can push and/or pull and various other tests to see at what level you can "function". If you refuse to do a test without a good reason they count it against you....at least that is what they told me when I did mine. I tried almost everything and if I could not do it I would tell them after I tried. Don't do anything that will worsen your condition but try what they want.....does that make sense?