MAS (Maximal Aerobic Speed)

MAS: what is it?

MAS answers the only question a coach really has about aerobic fitness: how fast can this client run when their engine is maxed out? It is the running-speed equivalent of VO2max, and the two are tightly linked, with the common field approximation putting VO2max in ml/kg/min at roughly 3.5 times MAS in km/h. Because MAS is a speed, it drops straight into a session plan. "6 x 3 minutes at 100% MAS" is something a client can execute on a track with a watch; "6 x 3 minutes at VO2max" is not.

How MAS is tested

All MAS tests are progressive: the athlete runs at a speed that rises in fixed steps until they can no longer hold it, and MAS is the last speed sustained for a full stage. The differences between protocols are the size of the step, the length of the stage, and whether the running is continuous or shuttle.

The continuous track tests with a 0.5 km/h increase every minute give the cleanest number because there is no turning cost. Shuttle protocols are far easier to run indoors with a group, but decelerating and turning every 20 metres costs energy that straight-line running does not, so a shuttle result and a track result on the same athlete are not interchangeable.

Turning MAS into training paces

The reason coaches test MAS is that everything downstream can be written as a percentage of it. The percentage sets the physiological target; the work and rest durations decide whether the session builds the top end or the base.

Short intervals around and slightly above MAS accumulate a lot of time near VO2max with tolerable fatigue, which is why 30 seconds on, 30 seconds off at 100 to 110% MAS is such a durable format. Longer intervals below MAS train the ability to hold a high fraction of the ceiling. Continuous work well under MAS builds the aerobic base.

Common testing mistakes

The biggest one is testing a client who has never run to a beep before. The first attempt measures their willingness to keep going as much as their fitness, so run a short familiarisation the week before and treat the second result as the real baseline.

The second is letting the warm-up vary. A client who arrives cold reaches the same stage feeling far worse than one who warmed up for fifteen minutes, and the difference is large enough to swallow a block of training. Write the warm-up into the protocol and use the identical one every time.

What MAS does not tell you

Two clients with the same MAS can perform very differently over 10 km, because MAS says nothing about how long they can hold a given fraction of it, and nothing about running economy. A client with excellent economy covers more ground for the same oxygen cost at any sub-maximal pace.

MAS is also surface- and mode-specific. A cyclist has a maximal aerobic power, not a speed, and a swimmer has a maximal aerobic velocity in the water. Do not carry a running MAS across to the bike, and re-test on the surface the client actually trains on.

• Re-test every 6 to 12 weeks, on the same protocol and the same surface.
• Round the result to the nearest 0.5 km/h. Anything finer is false precision.
• For team-sport athletes, pair MAS with a repeated-sprint test; MAS alone misses the anaerobic side.
• Rest at least 48 hours before the test, and never test on the back of a heavy leg session.