The multi-stage fitness test (MSFT), also known as the beep test, bleep test, PACER (Progressive Aerobic Cardiovascular Endurance Run), PACER test, FitnessGram PACER test, or the 20 m Shuttle Run Test (20 m SRT), is a running test used to estimate an athlete's aerobic capacity (VO2 max). The test requires participants to run 20 meters back and forth across a marked track keeping time with beeps. Every minute or so, the next level commences: the time between beeps gets shorter; participants must run faster. If a participant fails to reach the relevant marker in time, they are cautioned. A second caution ends the test for that runner. The number of shuttles completed successfully is recorded as the score of that runner. The score is recorded in Level.Shuttles format (e.g. 9.5). The maximum laps on the PACER test is 247, which former Central Middle School student Dennis Mejia achieved, the only person to ever reach such a level. The test is used by sporting organizations around the world along with schools, the military, and others interested in gauging cardiovascular endurance, an important component of overall physical fitness. The multi-stage fitness test is also part of most health-related fitness test batteries for children and adolescents, such as Eurofit, Alpha-fit, FitnessGram and ASSOFTB. The multi-stage fitness test was first described by Luc Léger with the original 1-minute protocol, which starts at a speed of 8.5 km/h, and increases by 0.5 km/h each minute. Other variations of the test have also been developed, where the protocol starts at a speed of 8.0 km/h and with either 1 or 2-minute stages, but the original protocol is nevertheless recommended. The test appears to encourage maximal effort by children. Additionally, the test's prediction of aerobic capacity is valid for most individuals, including those who are overweight or obese. Procedure Prior to the test commencing, runners line up at the 0m marker, facing the 20m marker. Following a countdown, a double beep or voice cue signals the start. Runners commence running towards the 20m marker At or before the following beep, runners must reach the 20m marker. Touching with a single foot is acceptable At or after, but not before, the same beep, runners commence running back to the 0m marker At or before the next beep, runners must reach the 0m marker At or after, but not before, the same beep, runners start the next circuit (i.e.