Maximal Aerobic Speed: The One Number That Sets Every Training Pace

A speed you can measure, not a heart rate that drifts

Run progressively faster and your oxygen uptake climbs almost in a straight line with speed — until it stops climbing. The speed at which it first stops is maximal aerobic speed. Go faster than that and you certainly can, for a while, but the extra energy no longer comes from oxygen; it comes from anaerobic sources you cannot refill on the move. So MAS is a ceiling with a very specific meaning: the fastest pace your aerobic engine alone can support, and the slowest pace at which that engine is fully open.

The practical value is not the physiology but the unit. MAS is expressed in miles per hour, which means every zone below it can be expressed as a pace you can actually run. Heart rate cannot do that. It drifts upward by five to ten beats over an hour at unchanged pace, it lags a change of effort by 30 to 60 seconds, and it responds to heat, dehydration, sleep debt, caffeine and altitude before it responds to anything you are trying to train. Ask a runner to hold 85% of maximum heart rate and you have asked for something that means a different pace on Tuesday than it did on Sunday. Ask for 85% of MAS and you have asked for 7:04 per mile.

The three field tests, and what each one actually measures

The half-Cooper is six minutes as hard as you can sustain, on a track, and the arithmetic is unusually kind. Six minutes is exactly one tenth of an hour, so your distance in miles multiplied by ten is your speed in miles per hour. Cover one mile and your MAS is 10 mph; cover 0.9 of a mile and it is 9 mph. Six minutes is not an arbitrary length. Time to exhaustion at MAS — the literature calls it tlim — runs from about four to eight minutes in trained runners, with a median close to six, so a maximal six-minute effort lands almost exactly on the speed that just elicits VO2max.

The VAMEVAL, designed by Georges Cazorla and Luc Léger, is a graded test rather than a time trial. You start at 8 km/h and the speed rises by 0.5 km/h every minute; cones set at 20 m intervals round the track tell you, beep by beep, whether you are still on schedule. The last stage you complete is your result. It is a metric protocol by origin and it reports in km/h, so English-speaking runners convert once at the end and then work in min/mile. Because the test ramps rather than asks for a flat-out effort, it is far more forgiving of poor pacing than a six-minute trial — which is its main advantage, and the reason clubs use it on whole groups at once.

The five-minute time trial is the simplest of the three: run five minutes as hard as you can hold and your average speed over those five minutes is your MAS. It sits at the short end of the tlim range, so it tends to read a shade high for runners who can hold MAS for eight minutes and a shade low for those who fold at four. That is the honest summary of all three: the six-minute and five-minute tests measure an average speed over a fixed duration, and the VAMEVAL measures the speed at which you stop. They agree closely for most runners and diverge for the ones whose tlim is unusual. Pick one, and then always retest with that one.

One number, the whole training week

The table above takes a single MAS of 10 mph and turns it into seven paces. Notice how far apart the ends are: recovery running at 60% is 10:00 per mile, and the 110% strides are 5:27 — the same runner, the same week, a gap of four and a half minutes per mile. Most training errors live in the compression of that range. Easy days drift to 75% because 75% feels virtuous; interval days settle at 95% because 105% hurts. Percentages of a measured speed are the cure, because they are checkable on a lap split.

There is a physiological reason the percentages behave well. Below MAS the oxygen cost of running rises roughly in proportion to speed, so 70% of MAS is close to 70% of VO2max. Percentages of maximum heart rate do not have that property at all: 70% of maximum heart rate corresponds to something nearer 55% of VO2max, and the mapping shifts with age and fitness. When a plan says an interval should be run at VO2max, a percentage of MAS delivers that literally; a percentage of heart rate delivers an approximation with a 30-second delay built in.

MAS is not VO2max, and running economy is the difference

The two are related by one equation and separated by one term. VO2max is the size of the engine, measured in millilitres of oxygen per kilogram per minute. Running economy is how much oxygen a mile costs you, measured in millilitres per kilogram per mile. Divide the first by the second and you get a speed: MAS = VO2max ÷ economy. A common English-language shorthand is that each mile per hour costs about 5.6 ml/kg/min, which corresponds to an economy of roughly 338 ml/kg/mile — so a 10 mph runner at that economy has a VO2max near 56.

Now hold VO2max fixed at 56 and vary only the economy, which in real runners spans a wide band. At 320 ml/kg/mile, MAS is 56 ÷ 320 × 60 = 10.5 mph, a pace of 5:43. At 350 ml/kg/mile it is 56 ÷ 350 × 60 = 9.6 mph, a pace of 6:15. That is 32 seconds per mile between two runners whose laboratory VO2max is identical to the decimal — more than three minutes over a six-mile race. If you have ever watched someone with worse numbers than you beat you comfortably, this term is the usual explanation.

This is also why MAS predicts race performance better than VO2max does. VO2max is largely a central property — heart, blood, lungs — and it responds slowly and hits a ceiling. Economy is mechanical and neuromuscular: it improves with years of mileage, with strength and plyometric work, with cadence and with better shoes, and it keeps improving long after VO2max has stopped. MAS is the product of both, which makes it the honest single number. It is also why you should not chase a laboratory VO2max figure at all: the speed is what you race on.

Why sessions at 100% are always short

If time to exhaustion at MAS is four to eight minutes, then a continuous run at 100% cannot last longer than that by definition — and a session that intends to accumulate 15 or 20 minutes at VO2max has to be broken up. That is the entire logic of short intervals. Six repetitions of one minute at 100% with a minute of jogging between them accumulates six minutes at MAS while feeling far more manageable than a single six-minute effort, because oxygen uptake stays high through the short recoveries. Thirty seconds on, thirty seconds off accumulates more still.

Above 100% the arithmetic of the zone table keeps working but the physiology changes. A 105% or 110% repetition is no longer purely aerobic; the surplus comes from anaerobic stores, which is why those repetitions have to be short and why full recovery between them is not laziness. They are trained for a different reason — mechanical speed reserve, the ability to change pace late in a race — and treating them as extra VO2max work is a reliable way to arrive at the start line tired.

Where the number goes wrong

Test conditions leak straight into the result. A treadmill has no air to push through and a belt that helps the leg back under you, so a treadmill test reads high unless you set the incline to 1%. Wind on an exposed track costs more into it than it gives back with it. Heat, altitude and a soft surface all pull the number down. None of that matters if you always test the same way — the whole point of MAS is to be a reference you can compare against itself — but it matters enormously if you test on the track in April and on the treadmill in November and then wonder why you have got worse.

The second failure is staleness. MAS moves with training, and a set of zones built on a number from five months ago will be too easy in some places and too hard in others at exactly the same time. Retest every six to ten weeks, or at the start of every training block, and rebuild the table from the new value. A stale MAS is worse than no zones at all, because it looks precise.

Frequently asked questions

Is maximal aerobic speed the same thing as vVO2max?

For training purposes, yes. vVO2max is the laboratory term for the slowest treadmill speed that elicits maximal oxygen uptake; MAS is the field estimate of the same quantity. Purists note that a graded laboratory protocol and a six-minute field test do not always land on the identical figure, and they are right — differences of a few tenths of a mile per hour are normal. That is not a problem as long as you use one method consistently and compare each result against the last one from the same method.

Can I read my MAS off a race result instead of running a test?

Roughly, and the roughness matters. For a trained runner, 3,000 m race pace usually sits between 95% and 100% of MAS, and 5,000 m pace between 92% and 95%. So a 5,000 m race gives you a defensible starting estimate — divide your race speed by 0.93 and you are close. But the spread across individuals is real, and it is driven by the same tlim variation that makes the field tests disagree. Use a race as a sanity check on a test, not as a replacement for one.

Why do my easy runs feel too fast at 70% of MAS?

Usually because the MAS you are using is too high. An over-read comes from testing on a treadmill without a 1% incline, testing with a strong tailwind on the fast straight, or pacing a six-minute test so aggressively that it was really a four-minute test with a jog attached. Retest properly, and if the number holds, drop your easy running to 60-65% for a few weeks. Easy running is meant to be easy; if a zone and your legs disagree, the legs are the better instrument.

Does the same idea exist for cycling and swimming?

Yes, with different names. Cyclists use maximal aerobic power, the power output at which VO2max is reached, expressed in watts rather than speed — because on a bike speed depends on wind and gradient while power does not. Swimmers use critical swim speed, derived from two time trials over different distances. Triathletes end up carrying all three, which is exactly why a pace calculator that converts between them is worth having open on race week.

How much can MAS actually improve?

A beginner can gain a great deal in a first season, mostly through economy and the sheer novelty of running. A trained runner should expect much less from VO2max, which plateaus, and much more from economy, which does not. That asymmetry is worth knowing before you choose a training block: if your MAS has been flat for two years while your interval sessions have got harder, the missing lever is probably strength, cadence and hill work rather than another month of 30/30s.