Rusty this is for you......
The beep test, also known as the bleep test, multi-stage fitness test, or shuttle run test, is used by sports coaches and trainers to estimate an athlete's maximum oxygen uptake better known as VO2 Max. The beep test is especially useful for players of sports like football, hockey, or rugby. The beep test involves running continuously between two points that are 20 meters apart (also found in 15 meters). These runs are synchronised with a pre-recorded audio tape, CD or laptop which plays beeps at set intervals. As the beep test proceeds, the interval between each successive beep reduces, forcing the athlete to increase velocity over the course of the beep test, until it is impossible to keep in sync with the recording.
Reference: The Beep Test
Thanks for your replies. So far the only dedicated website to the beep test which I found is the reference site. Quite good and found some interesting information. According to them Lance Armstrong is one of the very few people who can complete all 23 levels!