The Yo-Yo test is a maximal aerobic endurance fitness test, involving running between markers placed 20 meters apart, at increasing speeds, until exhaustion.

The test was developed in the 1990s by the Danish soccer physiologist Jens Bangsbo and his colleagues, and is now one of the most commonly conducted fitness test around the world. There are quite a few variations of the yo-yo test (see Yo-Yo Test Versions), though the most commonly used version is the Yo-Yo Intermittent Recovery Test Level 1, also called YYIRT1, IR1, or something like that.

It is this intermittent recovery test that most people will mean when they talk about the yo-yo test, and is the version that most teams will be using for testing their athletes. the yo-yo test layout Yo-Yo Intermittent Recovery Test Level 1 involves running between two markers 20 meters apart, following audio cues which dictate the running speed required.

After each 40 meters run, the participants have an active break of 10 seconds before running 40 meters again. At regular intervals, the required running speed increases.

The test continues until the participants are no longer able to keep up with the required pace. The yo-yo test was developed primarily for football (soccer) players, though it is becoming a popular test for many team sport athletes, with even the Indian cricket team using it as a selection criteria.

The Australian football draft combine have replaced the beep test on their testing program with the yo-yo test, and we may see this happen more as the yo-yo test is seen as more specific for the intermittent-type field running sports..