Gacon 45/15 Test
Designed by Georges Gacon, this test alternates 45 seconds of effort and 15 seconds of recovery over a distance that grows with every level, from 125 to 312 metres, with intensity rising at each cycle, to measure your MAS precisely.
By Jérémie NeubauerSite editor; runner, CrossFit and strength athlete for over 15 years · protocol checked against sources on
About the Gacon test
Often called the intermittent test or the 45/15 MAS test, this progressive, incremental test alternates effort and recovery sequences to measure Maximal Aerobic Speed precisely. It was designed by Georges Gacon, a PE teacher and strength and conditioning coach.
The test alternates sequences of 45 seconds of intense effort and 15 seconds of recovery. The format is easy to set up and needs no complex equipment.
How the test works
The athlete runs at an increasing intensity for 45 seconds, followed by 15 seconds of walking or slow jogging. The intensity rises progressively after each complete cycle, making the test harder and harder until exhaustion. It assesses both general aerobic fitness and the ability to sustain effort under progressive fatigue.
Calculator
Calculate your MAS
Select the last level you completed to get your estimated MAS.
Doing the test yourself
You can run this test alone. The main requirement: access to a track or flat surface with where up to 312 metres can be measured out.
- A suitable venue: athletics track or flat, obstacle-free ground
- Floor markers every 6.25 m from 125 m (one marker = one level)
- A stopwatch or a watch with a timer (45 s / 15 s)
- Proper sports clothing, with suitable running shoes
Protocol
How the test unfolds
- Prepare your equipmentComfortable running shoes, a stopwatch or timing app, and something to hydrate with.
- Mark the distanceOn a track or flat path, place a first marker 125 m from the start, then one every 6.25 m: each marker is one level.
- Warm upA good warm-up (easy jogging, dynamic stretches) to avoid injury.
- Start the testRun to your level’s marker in 45 seconds, then walk for 15 seconds. Increase the speed at each interval until exhaustion.
Reference chart
The full 31-level chart
| Level | Speed | Distance / 45 s | Time per 100 m |
|---|---|---|---|
| 1 | 10 km/h | 125.00 m | 36.00 s |
| 2 | 10.5 km/h | 131.25 m | 34.29 s |
| 3 | 11 km/h | 137.50 m | 32.73 s |
| 4 | 11.5 km/h | 143.75 m | 31.30 s |
| 5 | 12 km/h | 150.00 m | 30.00 s |
| 6 | 12.5 km/h | 156.25 m | 28.80 s |
| 7 | 13 km/h | 162.50 m | 27.69 s |
| 8 | 13.5 km/h | 168.75 m | 26.67 s |
| 9 | 14 km/h | 175.00 m | 25.71 s |
| 10 | 14.5 km/h | 181.25 m | 24.83 s |
| 11 | 15 km/h | 187.50 m | 24.00 s |
| 12 | 15.5 km/h | 193.75 m | 23.23 s |
| 13 | 16 km/h | 200.00 m | 22.50 s |
| 14 | 16.5 km/h | 206.25 m | 21.82 s |
| 15 | 17 km/h | 212.50 m | 21.18 s |
| 16 | 17.5 km/h | 218.75 m | 20.57 s |
| 17 | 18 km/h | 225.00 m | 20.00 s |
| 18 | 18.5 km/h | 231.25 m | 19.46 s |
| 19 | 19 km/h | 237.50 m | 18.95 s |
| 20 | 19.5 km/h | 243.75 m | 18.46 s |
| 21 | 20 km/h | 250.00 m | 18.00 s |
| 22 | 20.5 km/h | 256.25 m | 17.56 s |
| 23 | 21 km/h | 262.50 m | 17.14 s |
| 24 | 21.5 km/h | 268.75 m | 16.74 s |
| 25 | 22 km/h | 275.00 m | 16.36 s |
| 26 | 22.5 km/h | 281.25 m | 16.00 s |
| 27 | 23 km/h | 287.50 m | 15.65 s |
| 28 | 23.5 km/h | 293.75 m | 15.32 s |
| 29 | 24 km/h | 300.00 m | 15.00 s |
| 30 | 24.5 km/h | 306.25 m | 14.69 s |
| 31 | 25 km/h | 312.50 m | 14.40 s |
Calculating and interpreting your MAS
Note the last speed reached at the moment you were forced to abandon the required pace: that speed is your MAS. The higher the level, the better your aerobic fitness. A lower ceiling simply gives you a baseline to train against.
Recommended gear
To run the test in good conditions
- Sports stopwatch View on Amazon →
- Set of training cones View on Amazon →
- Running shoes View on Amazon →
Amazon affiliate links: if you buy, this site earns a commission at no extra cost to you.
Frequently asked questions
FAQ
Why 45 seconds of effort and 15 of recovery?
This intermittent format (45/15) alternates effort and short recovery to push the body progressively towards its MAS, while staying feasible without laboratory equipment.
What is the difference with the beep test?
The beep test is a continuous 20 m shuttle effort, whereas the Gacon test alternates cycles of 45 seconds of effort over a distance that grows with every level, from 125 to 312 m, and 15 seconds of walking recovery. This format is closer to interval training.
Do you need someone with you for this test?
No, it can be done alone with a stopwatch, but a partner or coach makes counting cycles and reading the time much easier.
What is the advantage of the intermittent format over a continuous effort?
Alternating effort and recovery lets you hold an intensity close to your MAS for longer than in a continuous test, which makes the test both more tolerable and closer to the real efforts found in team sports.