The bleep test or multistage fitness test was adapted from the Montreal Track Test in 1982 to provide a test that could be completed in a smaller area without the need for a track. The test requires you to run between two markers 20m apart, in time with an increasingly fast beep.
At the end of each ‘stage’ the time between beeps will decrease meaning you must run faster to complete the stage. While originally designed as a predictor of VO2 max, research now suggests this may not be the case. But that doesn’t change the fact that it’s a repeatable test of how aerobically fit you are. So, useful for triathletes? Yes. The most appropriate test? Probably not.
Taking a step back to the Montreal Track Test may be more suitable for triathletes due to the continuous nature of the run rather than the stop/start, quick turning required in the bleep test. The Montreal Track Test requires you to run continuously round a track, making it to 50m markers before the beep/whistle. As with the bleep test, the stages are made increasingly difficult by having to run faster to make it to the next marker.