High VO2 Max But Still Slow? What the Number Misses
Patricia Bedoya
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6
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Cover image generated with AI — © Chubby Studio S.L.
KEY TAKEAWAY
VO2 max is a ceiling, not a speed. Three other things decide how much of it you can use: the pace you can hold at threshold, how much oxygen that pace costs you, and whether both survive a long effort. In 78 half-marathon runners, threshold speed tracked race time at r = -0.92 while VO2 max managed -0.75 and -0.59, and the best predictive equations left VO2 max out entirely.
If your VO2 max reads high and your race times do not match it, nothing is broken. VO2 max is a ceiling, not a speed. It tells you how much oxygen your body can use per minute at absolute maximum, which is a real measure of aerobic capacity. What it does not tell you is how much of that capacity you can hold for an hour, how much oxygen your particular stride burns at a given pace, or whether either of those still holds up ninety minutes into a long effort. Those three things are where race pace actually comes from, and they are trained separately.
What does a high VO2 max actually promise?
Headroom, and only headroom. In their review of endurance performance, Joyner and Coyle put elite endurance athletes between 70 and 85 mL/kg/min, roughly 50 to 100 percent above sedentary values, achieved mostly through a heart that moves more blood per beat. That capacity is worth having. But a ceiling only tells you where the roof is. A high VO2 max buys you a large aerobic ceiling and nothing else, and the rest of the model decides how close to it you get to live.
The gap shows up most clearly in the fraction. Untrained people reach the point where blood lactate climbs sharply at around 60 percent of their VO2 max. Trained athletes hold 75 to 90 percent before that happens. Two runners with an identical ceiling and a fifteen point gap in that fraction are not running the same race, and the one with the lower ceiling and the higher fraction usually wins it. If you want the mechanism underneath the number first, we wrote what VO2 max actually measures as a standalone piece.
Why do two people with the same VO2 max race differently?
Because VO2 max is one of four inputs, and it happens to be the only one most people can see. The other three are the fraction of it you can sustain, the oxygen cost of moving at a given speed, and how well both of those survive a long effort. Each is measured differently, each responds to different training, and none of them appears on your wrist.
This is not a subtlety at the edges. Joyner and Coyle note that athletes matched on both VO2 max and lactate threshold still record substantially different endurance times, and they are blunt about why that is hard to fix: the physiological determinants of running economy, they write, generally remain a mystery. So the honest answer to why you are slower than someone with your numbers is often that the difference sits in a variable nobody can read off a wrist and nobody fully understands.
The practical consequence is that a high ceiling with slow times is not a contradiction to resolve. It is a fairly precise description of where your training has been. Ceilings respond to hard work near maximum. The other three respond to volume, to sustained work at threshold, and to time spent going long.
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What predicts race pace better than VO2 max?
The speed you can hold at threshold. A 2017 study of 78 male half-marathon runners measured VO2 max, threshold speed, peak treadmill speed, body composition and stride mechanics, then checked which of them tracked finishing time. VO2 max correlated at r = -0.75 in the first group and -0.59 in the second. Threshold speed correlated at -0.92 in both. When the researchers built their predictive equations, the two best ones dropped VO2 max entirely and used peak speed and threshold speed instead.
That is worth sitting with, because it inverts the usual hierarchy. The number everyone quotes was the weaker predictor. The number almost nobody tracks was the stronger one, and it is also the more trainable of the two, which is the part you can do something about.
How much does running economy vary between people?
More than most people expect. Oxygen cost at the same running speed varies by 30 to 40 percent between individuals, so two people with identical ceilings can be doing very different amounts of work to hold the same pace. Economy is why a training partner who looks unremarkable on paper quietly drops you on a hill.
It is also stubborn. The same review describes case studies where years of training produced improvements of roughly 1 to 3 percent a year. That is meaningful across a decade and invisible across a month, which is exactly the wrong shape for anyone hoping a six week block will fix it. Economy improves as a by-product of accumulated running, not as a target you can aim at directly.
Does your ceiling survive two hours?
This is the newest piece of the picture and the one that explains the most about long races. Researchers now treat durability as a fourth dimension of endurance performance: how well your physiology holds its shape after prolonged work. A 2025 methodological review in Experimental Physiology summarises what happens after roughly 120 minutes of heavy cycling. Critical power fell by about 10 percent on average, and by anywhere from 1 to 31 percent depending on the person. Threshold velocity dropped by a similar amount, with the same wide spread.
Nothing in a lab test at minute zero predicts that spread. Someone can start with a high ceiling and a high threshold and lose a third of it by the point in the race where it matters. If your 5k times look fine and your half marathon falls apart, durability is a more likely explanation than aerobic capacity, and the answer is long steady work rather than more intervals.
Does a wrist estimate change any of this?
Not the logic, but it should change how much weight you put on the input. Your watch does not measure VO2 max, it predicts it from heart rate and pace during outdoor walks and runs, which is why a low cardio fitness reading on your watch often says more about the conditions than about you. A generous estimate paired with slow times may partly be the estimate, so how close a wrist VO2 max gets to a lab test is worth knowing before you build a theory on it. Treat it as a trend line and a poor absolute.
So what should you actually train?
Whichever of the three you have neglected, which for most people with a high ceiling is the boring one. Threshold speed responds to sustained work at a pace you could hold for around an hour, done regularly rather than heroically. Economy and durability respond to aerobic volume, which is what easy aerobic work is actually for. The three levers under your ceiling move faster than the ceiling itself does, and they are what your race pace is made of.
One caveat worth keeping. Adding volume raises the cost of the week, and that cost is personal: the same session lands differently on two people, which is what your own cardiac load is measuring. Building the parts that make you fast is a months-long project, and it only works if you are still doing it in month four.
When slow is not a training problem
Sometimes the answer is not in the model at all. Heat, altitude, a hilly route, poor sleep, illness, iron status and a long list of medications all change what your body can do on a given day without changing anything about your capacity. If your pace has fallen away over months alongside real fatigue, breathlessness, or symptoms that feel wrong, that is a conversation with a doctor rather than a training block. FitWoody informs, it does not diagnose.
Frequently asked questions
Is a high VO2 max useless if I am slow?
No. A high VO2 max is a real aerobic ceiling and a strong marker of cardiovascular health, and it is the platform everything else is built on. It just is not a prediction of race pace by itself. Performance depends on the fraction of that ceiling you can sustain, how much oxygen your movement costs, and whether both hold up over a long effort. A high ceiling means you have room to get considerably faster without raising it at all.
Can you get faster without raising your VO2 max?
Yes, and for most trained people that is where the remaining gains are. VO2 max tends to plateau after the first year or two of consistent endurance training, while threshold speed, running economy and durability keep improving for years. In a study of 78 half-marathon runners, threshold speed predicted finishing time far better than VO2 max did, and the best predictive equations left VO2 max out.
Why is my VO2 max higher than faster runners I train with?
Most often because they hold a higher fraction of their ceiling and move more economically than you do. Oxygen cost at the same speed varies by 30 to 40 percent between people, so a partner with a lower ceiling can genuinely be doing less work at your pace. It can also be the estimate: a wrist VO2 max is predicted from heart rate and pace rather than measured, so treat it as a trend rather than a ranking.