This is one of the most objective evaluations available for doctors to tell what you are physically capable of doing. It is in your best interest to do what you are asked to do to the best of your ability. If you do less, this test is designed to detect that. Self-limiting behavior is fairly easily detected during an FCE. So is pain behavior that does not match the accepted injury.

I once handled a worker's compensation claim on an injured worker who decided she would show up in bad shape for her FCE. What she didn't know is that her employer had ordered surveillance and caught her engaged in activity beyond her restrictions during the week prior to her FCE. Her file and case were promptly handed over to the fraud division . . . .

I don't recommend ever trying to skew results of test for any kind of disability or insurance evaluation. It is just not worth it.

As for what the FCE will measure, that is specific to what part of the body was injured, what kind of injury you had, and your job description. They most likely would not test your back for an injury to the upper extremity, or hand dexterity for a knee injury, for example. If you can't work, it will be evident in the results. And most FCEs are performed by physical therapists, as far as I know.