The INTER test was proposed by Aandstadt and colleagues (1 - see reference below).
It consists of running a 20-meter distance at a constant pace, sprinting in change-of-direction manner, straight line sprinting and a recovery phase.
The test consists of different stages. In each stage, the running velocity of the 20-meter distance is controlled with an acoustic signal, whilst the change of direction and straight line sprinting is performed in an all out manner.
At the beginning of the test, the player ran 20 meters (1st shuttle) from line A to line B, then turn and ran back to line A. Another 4 shuttles (and therefore a total of 6 shuttles) are performed according to the running speed given by the audio signal.
The authors stated that the running velocity is in accordance to the 20-meter shuttle run test by Leger et al. (2) and increased 1.5 km/h for every level, starting from 8.0 km/h.
After the 6st shuttle the audio CD will announce the change of direction part, which consists of (turning on line A), sprint around cone X and Y to line B, with clearing the line (line B) with one foot and a sprint back through line A. 45 seconds will be given to complete the change of direction part. 6 shuttles will then be completed by the player followed by the 25 m straight sprint (line A to line C).
The player will then walk back to line A. A total of 60 seconds are given to complete the sprint including the walking back. Level 2 will then commence. The level 1 is therefore completed in 5:12 minutes.
The test is terminated when the player is not able to follow the 20 m shuttle run pacer over three consecutive occasions (> 3 m from the desired line), or due to voluntarily stopping the test. I am guessing, the final score is the completed distance of the test, prior termination.
Total run and sprint distance in each level was ~432 meter in addition of walking back (50 meters). The total time to complete level 1.
The test seems to be reliable and valid (1).
To our knowledge (and due to the publication date) there seems to be no scientific information on the INTER test, neither has any publication used this test in a soccer environment.
1. Aandstad, A. and Simon, E.V. Reliability and validity of the soccer specific INTER field test. J. Sports.
2. Leger, L.A., Mercier, D., Gadoury, C., and Lambert, J. The multistage 20 metre shuttle run test for aerobic
fitness. J. Sports. Sci. 6: 93-101, 1988.