A shuttle run is an extreme level cardiovascular endurance test. It is used to test people entering into usually physically demanding work feilds. Here in Canada, alot of our police departments use this for there entrance qualification test.
Basically you run between two points usually in a gym, 20 meters apart. While running back and forth you must keep up with a taped audio signal. In the begining it is a light jog but as time progresses it turns into a sprint back and forth. This test has replaced the old mile and a half runs that were once done.
At each end of the course you have two traffic cones, one at 20 meters and a warning line at 18 meters. You must keep up to the pace and never miss two cones in a row. If you are late at one side you must still pass the warning and always pivot at the end line then sprint to the other side and make the warning line before the beep. This is where it gets difficult as the pace only increases so you get no recoup time.
I am in policing in Canada and have done this test multiple times and depending on which level you must achieve it can be very difficult. Every 1 minute the pace increases. To qualify to be hired here you must complete 7.5 levels which is 7.5 minutes, not too bad. Any questions?