If you came of age in the U.S. during the past 40 years, there's a good chance that you have memories (fond or otherwise) of the President's Challenge fitness test. Remember? If you successfully performed five physical activities -- from pull-ups to shuttle runs -- you received a certificate signed by the president, officially declaring your physical fitness.
But as adults, it's not always as easy to know where we rank on the fitness scale or how we compare to others our age. Sure, we try to make it to the gym on a regular basis. We lift some weights and ride the elliptical to work up a sweat. But really, how fit are we?