MAS Calculator — Maximal Aerobic Speed and vVO2max

What MAS Is

Maximal aerobic speed — also written vVO2max — is the lowest running speed at which you reach VO2max. Run slower and oxygen uptake plateaus below maximum; run faster and you get there sooner but cannot stay.

It is useful for one specific reason: it collapses aerobic power and running economy into a single number you can actually run at. Two runners with identical VO2max values can have MAS values a kilometre per hour apart, because one of them wastes less energy at speed. A session written as "105% of MAS for 3 minutes" scales to both of them. The same session written as "3:10 per kilometre" does not.

The Arithmetic Is Trivial

A 6-minute test needs no formula at all, because six minutes is a tenth of an hour:

MAS (km/h) = distance in metres / 100

1,800 m in six minutes is 18.0 km/h. That is unit conversion, not a model, and any page presenting it as a discovery is padding.

What is not trivial is the claim attached to the number.

What the Test Actually Measures

It measures the speed you held. Whether that equals the speed at which you reach VO2max depends on the protocol and on who is running it — and the literature does not agree:

• A validation of the 6-minute race test concluded it is valid for determining MAS in university endurance men, and that female athletes need a shorter test. That is a narrow population and an explicit sex-specific caveat.
• Studies of the Université de Montréal track test split. Two could not find a significant difference between MAS and the UMTT speed; another found the UMTT overestimates it.
• A review concluded that the criterion validity of incremental field tests and shuttle runs for examining MAS cannot be confirmed.

The reference method is gas analysis in a laboratory. Everything on this page is a proxy for it.

That does not make a field test useless — it makes it useful for a different thing. Tracking your own MAS with the same protocol, on the same surface, three times a year will tell you whether you are getting fitter. Comparing your field-test MAS to a published figure from a lab study will tell you very little.

Why 4 to 8 Minutes

MAS can only be held for a few minutes — commonly reported as four to eight in trained runners. That window is what makes the 6-minute test the standard choice: long enough that the effort is aerobically limited, short enough that it is close to the duration MAS can actually be sustained for.

It is also a built-in check on your pacing. If you could have held your test speed for fifteen minutes, that speed is below your MAS and you paced it too conservatively. If you faded badly in the last ninety seconds, you went above it and the average is not a steady-state speed.

Prescribing Intervals From It

The percentage-of-MAS table on this page is a planning convention, not a set of findings. What the evidence does support is the mechanism underneath it: the stimulus is time spent at or near vVO2max, and short repetitions accumulate more of that time than long ones, because they delay the point at which you have to stop.

That is the whole argument for the 30-30 format — thirty seconds at about 105% MAS, thirty seconds easy, repeated. Each repetition is too short to drain you, oxygen uptake does not fall all the way back down in the recovery, and you can accumulate ten or fifteen minutes near VO2max in a session where three-minute repetitions would get you four.

Two practical points the percentages do not tell you:

Convert to distance, not pace. A watch showing instantaneous pace is useless over thirty seconds — it lags, it smooths, and you spend the repetition chasing a number. Mark out the distance instead. This page gives it for every session.

120% MAS is not an aerobic session. The speed-rep row exists because the paces are sometimes wanted, not because running at 120% of MAS develops aerobic power. Above about 110% you are training something else.

VO2max From MAS

The VO2max estimate here comes from the ACSM running equation:

VO2 = 0.2 × speed in m/min + 3.5

Which gives 63.5 ml/kg/min at 18 km/h. Two things that makes it:

It is a population-average relationship. The 0.2 coefficient is the average oxygen cost of running a metre per minute, and individual economy varies around it by enough to matter. A runner with excellent economy will have a genuinely lower VO2max than this equation reports from their MAS — and will race the same as someone with a higher one.

The +3.5 is a convention, standing for resting metabolic rate at 1 MET. It is a constant added to everyone regardless of their actual resting rate.

So treat it as an estimate derived from an estimate. If you want a number to train from, MAS itself is the more useful of the two, because it is the thing you can run.

Where This Sits Against the Other Tools Here

MAS is one anchor for training intensity. Threshold is another, and they are not interchangeable — MAS sits above threshold, and the gap between them varies enormously between runners. If you want the boundary rather than the ceiling, the lactate threshold calculator measures it from a 30-minute time trial instead of assuming where it falls as a percentage of MAS.

For VO2max specifically, the VO2 max calculator covers the other estimation routes, and for pacing a race off a recent result the marathon race predictor is the right tool.