When a new runner visits my lab and asks, “How can I raise my VO2max?”, I know exactly what they’re thinking. In the world of sports physiology, that single number has become a stand-in for fitness itself. It carries weight — I’ve published my share of papers on measuring it. But chasing that value with blinders on often steers athletes away from the gains that actually show up on race day. My name is Dr. Kenji Ota. Over twenty years of testing everyone from Olympians to heart-failure patients, I’ve learned that VO2max matters. But it’s not the whole story.
What VO2max Actually Tells You
Maximal oxygen uptake is the highest rate at which your body can pull in, move, and use oxygen when you’re pushing to the limit. It reflects the combined capacity of your lungs, heart, blood, and mitochondria. In my lab, we measure it with a metabolic cart while an athlete runs or cycles until they simply can’t continue. The result, in millilitres of oxygen per kilogram of body weight per minute, has real predictive power. A low VO2max is a strong, independent red flag for all-cause mortality. For a masters athlete, seeing that number climb after a training block confirms that central adaptations have taken hold.
But that number is just a snapshot taken at the breaking point. It says almost nothing about what goes on during the 95% of a race that unfolds below that ceiling. An athlete with a VO2max of 70 mL/kg/min won’t automatically beat someone with 65. The reasons sit in physiology that a maximum value can’t capture.
The Efficiency Gap: Turning Oxygen into Speed
Picture two cyclists with the same VO2max. One grinds out 250 watts at ventilatory threshold; the other cruises at 280 watts with the same internal strain. The difference is gross efficiency — the ratio of mechanical work done to metabolic energy burned. For runners, the equivalent is running economy. It can swing by 20–30% among athletes who share an oxygen-uptake ceiling.
I remember a national-level triathlete whose VO2max hadn’t moved in two years. Her coach was frustrated. When we dug into her submaximal data, we saw that her oxygen cost at marathon pace had dropped by 8%. She was spending less energy for the same output. That shift came from quiet improvements in tendon stiffness, motor-unit recruitment, and mitochondrial coupling — things a VO2max test never sees. She later set a personal best at the 70.3 distance. Not because her engine got bigger, but because her chassis got more efficient.
Why Efficiency Often Trumps Capacity
In any event longer than about eight minutes, it’s not the peak VO2max that calls the shots — it’s the fraction you can sustain. Two thresholds steer that fraction: the first lactate turn point and critical power (or the second threshold). Training that lifts those thresholds lets an athlete ride or run closer to their ceiling without blowing up. A sky-high VO2max paired with lousy metabolic fitness is like a sports car with a 20-litre fuel tank. Looks great on paper. Useless on a long drive.
Durability: The Trait That Vanishes in a Lab
A standard VO2max test is over in 8–12 minutes. Real endurance events stretch for hours, and fatigue brings a kind of physiological drift that no ramp test can fake. After 90 minutes of steady cycling, heart rate climbs while stroke volume and muscle efficiency slide. I call this loss of resilience “durability.” Two athletes with identical lab-measured VO2max and threshold power can look completely different after two hours of work. The one whose oxygen cost stays flat — and whose ventilatory efficiency doesn’t crumble — will race better, whether it’s a road event or a marathon.
Durability is tough to measure and even tougher to build. It hinges on muscle glycogen sparing, thermoregulation, and the ability to keep neuromuscular firing patterns intact when fatigue digs in. I often tell athletes to do a 5-minute max effort before and after a long, taxing session. If power drops or heart rate spikes at the same submaximal pace, that’s a durability gap. No single VO2max test will show you that.
When VO2max Is Most Useful
I’m not saying we should toss the measurement. In my clinic, VO2max gives me a baseline for risk stratification. If a sedentary person starts exercising and jumps from 25 to 35 mL/kg/min, that’s a real drop in cardiovascular risk — even if they never pin on a race bib. In elite sport, tracking VO2max across a season can tip a coach off to overtraining or incomplete recovery when numbers dip unexpectedly.
The metric also helps sort responders from non-responders. Some athletes show big central adaptations; others barely budge their maximal oxygen uptake but still get faster through peripheral changes. Knowing which bucket someone falls into lets us shape the programme instead of chasing a number with no context.
The Genetic Ceiling and Trainability
VO2max is about 50% heritable. Training can push it up 10–20% in most people, but the upper boundary is largely drawn by your genes. I’ve sat across from disappointed athletes who plateau at 55 mL/kg/min after years of grinding. Telling them their value is “average” for their age misses the point: their threshold power and economy might still be world-class. Obsessing over VO2max can blind us to what an athlete can actually do.
Better Ways to Track Progress
If you only measure VO2max, you’re missing most of the story. I steer athletes and coaches toward a small set of field tests that catch the deeper layers of endurance:
Submaximal heart rate drift. Warm up for 10 minutes, then hold a steady pace or power for 60–90 minutes. Look at the ratio of heart rate in the second half versus the first half, corrected for pace. That ratio reflects durability and metabolic efficiency. When it trends downward across months, you’re seeing real aerobic development — even if VO2max sits still.
Critical power or speed. Do two to three all-out time trials lasting anywhere from 3 to 20 minutes. The critical power (or critical speed) you derive is a solid predictor of endurance performance and picks up training effects better than VO2max alone. A rising critical power means you’re stretching the time you can hold near-max effort.
Economy at race pace. If you can get into a lab, measure oxygen consumption at your goal marathon pace or functional threshold power. No metabolic cart? Use heart rate and perceived exertion. Over a training cycle, a lower heart rate at the same pace — in roughly similar conditions — tells you your economy is improving.
Putting VO2max in Its Place
I still run VO2max tests every week. The data are clean, the physiology is sound, and the trend lines carry weight. But when an athlete sits across from me, I spend way more time on their submaximal data, their durability markers, and their efficiency trends. The highest VO2max I ever recorded belonged to a young cross-country skier. He never medalled at a national championship. His economy was poor, his thresholds were modest, and his durability fell apart after 40 kilometres.
The number is one piece of the puzzle. It tells you the size of the engine. Real endurance — the kind that wins races and stretches healthspan — is about how efficiently that engine runs, how long it can hold a high fraction of its output, and how well it stays together when fatigue sets in. Athletes who get this distinction train smarter and race better. I’ve seen it play out too many times to think otherwise.
Frequently Asked Questions
Can I estimate my VO2max from a smartwatch?
Consumer wearables use heart rate, pace, and algorithms to spit out a VO2max estimate. These numbers can be directionally useful for spotting trends, but they’re not a swap for lab measurements. Errors of 3–5 mL/kg/min are common, especially if your running economy is outside the norm. Treat the trend as a rough guide, not a hard benchmark.
Does age inevitably lower VO2max?
Yes, maximal oxygen uptake declines with age — but you have some say in how fast. Master athletes who keep up volume and intensity can slow the drop to about 5% per decade, versus the 10% seen in sedentary adults. The decline is driven by a falling maximal heart rate and stroke volume, but peripheral stuff like muscle capillarisation and mitochondrial density can stick around with steady training.
How often should I test my VO2max?
For most athletes, every 12–16 weeks is plenty. Testing more often rarely gives you actionable info and just adds fatigue. If you’re coming back from an injury or tracking a big training block, a test at the start and end can show central adaptations. In between, lean on the field tests I described above to watch your progress without the cost and hassle of a lab visit.
Is a higher VO2max always better for health?
Across a population, yes — climbing from a low to a moderate VO2max brings big health wins. But beyond a certain point, further bumps give you less and less for longevity. A value in the upper third for your age and sex lines up with the lowest mortality risk. Pushing for an extremely high VO2max through huge training volumes can raise injury risk and suppress your immune system without adding much health benefit.