2018 Berlin Marathon. Eliud Kipchoge broke the world record by 78 seconds with a time of 2:01:39 — the largest margin in marathon history. When physiologists reverse-engineered his performance, the numbers came in: VO₂max around 83–85 ml/kg/min, lactate threshold at 92% of VO₂max, running economy at 155–160 mL O₂/kg/km — among the most efficient ever measured. What stood out was this: Kipchoge’s VO₂max was not the highest on record. Norwegian skier Bjørn Dæhlie sat well above him at 96, and young cyclist Oskar Svendsen at 97.5 ml/kg/min. Kipchoge didn’t have the biggest engine — he was the athlete who ran his engine most efficiently and sustained it at the highest revolutions. Understanding VO₂max begins with grasping exactly this distinction.
Table of Contents
- What Is VO₂ Max? — Measuring the Size of the Engine
- What Limits VO₂ Max?
- Genetic Ceiling or Training Ceiling?
- Muscle Fiber Types and the VO₂ Max Relationship
- Sex Differences and Age Dynamics
- The Three Pillars of Endurance Performance
- Record Values Among Elites: What Do the Numbers Say?
- How to Improve Your VO₂ Max
- Conclusion: VO₂ Max Is the Start, Not the End
Figure: 5-zone training system — physiological effect by % of VO₂max. Each zone corresponds to different energy systems and sustainable durations. Bar length represents how long that intensity can be sustained.
What Is VO₂ Max? — Measuring the Size of the Engine
Maximal oxygen uptake (VO₂max) is the maximum amount of oxygen the body can use during exercise — expressed in milliliters per kilogram per minute (ml/kg/min). The concept dates back to the 1920s, to Nobel-laureate physiologist Archibald Vivian Hill and his colleague Hartley Lupton. Hill described how oxygen consumption plateaus at a certain point despite increasing workload — the “maximum oxygen uptake” [1]. A century later, this concept remains the cornerstone of endurance physiology.
VO₂max is understood through the Fick equation: VO₂max = Cardiac Output × Arteriovenous Oxygen Difference (a-vO₂ diff). Cardiac output is the volume of blood the heart pumps per minute (heart rate × stroke volume). The arteriovenous difference shows how much oxygen the muscles extract from the blood. For an elite skier with a VO₂max of 90 ml/kg/min and a body weight of 75 kg, absolute oxygen consumption is ~6.75 L/min. To supply that much oxygen, the heart must pump roughly 42 liters of blood per minute — equivalent to circulating a small adult’s entire blood volume every eight seconds.
In a VO₂max test, the athlete works at increasing intensities on a treadmill or cycle ergometer while breath-by-breath respiratory gases are continuously analyzed. The test takes 8–12 minutes. The plateau criterion is this: the increase in oxygen consumption drops below 150 ml/min despite rising workload. Additional verification indicators include a respiratory exchange ratio (RER) exceeding 1.10–1.15, heart rate approaching age-predicted maximum, and post-exercise blood lactate above 8 mmol/L. Treadmill tests yield 5–18% higher values than cycle ergometers — because more muscle mass is recruited.
What Limits VO₂ Max?
Contrary to common belief, the answer is not the lungs. In healthy individuals, the lungs can load far more oxygen into the blood than the heart can pump. Hemoglobin saturation remains at 95–98% even at VO₂max. Dempsey and colleagues’ research has established that the true bottleneck is not in the lungs but in cardiac output [2]. The lungs only become limiting at altitude or in respiratory disease.
There is an interesting exception: some elite athletes display exercise-induced arterial hypoxemia (EIAH) — the heart pumps blood at such a high rate that it passes through the pulmonary capillaries without fully oxygenating. Ron Clarke’s collapse at the 1968 Mexico City Olympics dramatized this exception: the holder of dozens of world records finished only sixth in the race at 2,240 meters when his arterial oxygen saturation dropped to dangerous levels. His engine was too powerful — but in the thin air, the fuel line couldn’t keep up.
The physiological hierarchy determining VO₂max ranks as follows: Primary — cardiac output, via left ventricular volume and stroke volume. Secondary — oxygen-carrying capacity, via hemoglobin concentration and blood volume. Tertiary — peripheral oxygen extraction capacity, set by mitochondrial density, capillary network, and enzyme levels.
Genetic Ceiling or Training Ceiling?
The HERITAGE Family Study systematically answered this question. 481 adults from 98 sedentary families completed a standardized 20-week aerobic training program. The results were striking: some individuals raised their VO₂max by 50%; others stayed below 5% after the same program [3]. About 47% of the variance in training response was attributed to genetic factors. The heritability of baseline VO₂max is 40–50%.
A second critical finding: baseline VO₂max did not correlate with improvement potential. Individuals with high initial values did not necessarily respond well; high responders were found among those with low starting values. One set of genes governed baseline VO₂max; an entirely different set governed training response. Hundreds of genetic variants have been identified — including ACTN3, ACE, PGC-1α (PPARGC1A), and EPAS1 — but no single one is an “endurance gene.”
Sedentary individuals can achieve 15–25% VO₂max gains in six months with consistent aerobic training. A 9-month program documented 19% gains in men aged 63 and 22% gains in women aged 64. But as you approach genetic potential, returns diminish. Marginal VO₂max improvements in elite athletes are extremely small — their gains come from threshold and economy.
Muscle Fiber Types and the VO₂ Max Relationship
Muscle fiber type distribution is an important determinant of VO₂max potential. Slow-twitch Type I fibers contain more mitochondria, a denser capillary network, and higher oxidative enzyme activity per unit volume — they are more efficient at power generation per unit oxygen and resistant to fatigue. David Costill’s classic studies showed that elite marathoners have 70–80% Type I fibers in their quadriceps and gastrocnemius — versus 35–45% in sedentary individuals. Fiber type distribution is largely innate and doesn’t radically shift with training. But training dramatically develops the oxidative capacity of existing fibers — PGC-1α, the master switch of mitochondrial biogenesis, is the primary molecular target of aerobic exercise.
Sex Differences and Age Dynamics
Women at similar training levels typically have 15–30% lower VO₂max than men. At elite level the gap narrows to 10–15%. The reasons are physiological: 10–20% lower hemoglobin concentration (less oxygen-carrying capacity), smaller heart volume and cardiac output, higher proportional body fat, and less muscle mass per kilogram of body weight. Adjusted for lean body mass, the gap narrows but doesn’t fully close. Joan Benoit Samuelson’s 78.6 ml/kg/min — measured in 1984, the year she won the first women’s Olympic marathon at Los Angeles — is among the highest values recorded in women. Despite undergoing knee arthroscopy before the Olympic trials, Benoit won the trials in 2:31:04 and then the final in 2:24:52.
Aging is inevitable but its pace is controllable. In children (pre-puberty) VO₂max is surprisingly high — 45–55 ml/kg/min in both boys and girls. In males it climbs to a peak around 17; in females it plateaus around 14. Decline begins after age 25–30: roughly 1% per year (~10% per decade) in sedentary individuals, 0.5–0.7% in active athletes. Maximum heart rate drops 5–7 beats per decade. Muscle mass and mitochondrial content decline (sarcopenia). A sedentary 70-year-old may drop below 20 ml/kg/min — the threshold of difficulty in daily activities. But veteran athletes training regularly in their 70s can maintain values in the 40s ml/kg/min range — equivalent to untrained 30-year-olds.
The Three Pillars of Endurance Performance
VO₂max sets the ceiling of endurance performance — but a ceiling alone doesn’t make the space livable. Joyner and Coyle’s comprehensive 2008 review established that performance rests on three core pillars [4].
First pillar — VO₂max (“engine size”): The ceiling capacity of the aerobic system. Strongly correlates with performance across heterogeneous groups; discriminates poorly within homogeneous elite groups. Trainable by 15–25%, with genetic ceiling determinative.
Second pillar — lactate threshold (“how much of the engine you can use”): 50–60% of VO₂max in untrained individuals; 85–90% in elite marathoners. Eliud Kipchoge runs at 92% of his VO₂max at marathon pace. It responds to training far more than VO₂max — threshold continues rising even after VO₂max plateaus.
Third pillar — Running economy (“fuel efficiency”): Oxygen cost at a given speed, expressed in mL/kg/km. Shows 20–30% variation between runners of similar VO₂max. Conley and Krahenbuhl’s classic study showed running economy was the strongest variable explaining 10K performance differences among national-level runners with similar VO₂max values. Kipchoge’s 155–160 mL O₂/kg/km is among the most efficient numbers measured. East African runners use 5–10% less oxygen at the same pace as runners with equivalent VO₂max — due to slender lower-leg architecture, high tendon elasticity, and running biomechanics built from childhood.
The effect of these three pillars is multiplicative, not additive. A modest gain in each produces a large jump in overall performance. Joyner’s 1991 calculation predicted a 1:57:58 marathon from the best physiologically possible combination of the three variables — twenty-eight years before Kipchoge ran 1:59:40 in 2019.
VO₂max is the size of your engine, lactate threshold is how fast you can drive without redlining, and running economy is your fuel consumption. Together they determine performance — none of them alone is sufficient.
<em>The Science of Human Endurance, Chapter 1</em>Record Values Among Elites: What Do the Numbers Say?
VO₂max values show striking differences across sports and individuals. The highest reliable measurement belongs to Norwegian junior cyclist Oskar Svendsen in 2012: 97.5 ml/kg/min — recorded while he was world junior time-trial champion. Norwegian cross-country skier Bjørn Dæhlie, at 1.83 m and 75 kg, has measurements of ~96 ml/kg/min with absolute oxygen consumption above 7.0 L/min, and eight Olympic golds. Greg LeMond at 92.5 and Spaniard Miguel Indurain at ~88 ml/kg/min (with absolute values reaching ~7.5 L/min due to his large frame) are among the highest recorded in history.
Among women, Joan Benoit Samuelson tops the list at 78.6 ml/kg/min. Norwegian Bente Skari at 76.6 and Swedish skier Charlotte Kalla at ~74 follow her. No woman has yet reached the 80s in peer-reviewed literature — but given the rapid growth in women’s sport, that ceiling is probably only a matter of time.
For population perspective: a sedentary 30-something falls in 30–40 ml/kg/min, a recreational runner 45–55, a club-level racer 55–65. Below 15–18 ml/kg/min represents difficulty even in basic daily activities — a clinically critical threshold. The value of these numbers is in perspective: no athlete can be told “your potential is this much” based on a single VO₂max value. The number captures a moment — the result of training history, nutritional status, test conditions, and genetic combination. The real question is what is done with that number.
How to Improve Your VO₂ Max
The physiological mechanism of training response is clear: endurance training increases left ventricular volume to raise stroke volume; expands plasma volume; develops muscle mitochondrial density and capillary network. Bengt Saltin’s famous bed-rest study (1968) showed that healthy young men lost 25% of their VO₂max with three weeks of inactivity. McGuire et al.’s 30-year follow-up confirmed that inactivity is more destructive than aging by decades [5].
Aerobic base work: High-volume, low-intensity training — below LT1, at conversational pace. Drives eccentric cardiac hypertrophy and plasma volume expansion. Elite marathoners run 160–240 km/week and 80% of that volume happens in this zone.
VO₂max intervals: 3–5 minute repetitions at VO₂max intensity with equal recovery. 6×4 minutes or 5×5 minutes are standard protocols. 1–2 sessions per week, applied during build phases.
Threshold training: If VO₂max is high but fractional utilization is low — that is, the engine is big but underused — tempo runs and cruise intervals push LT2 closer to VO₂max.
Running economy work: High mileage and biomechanically focused training. Tendon elasticity, motor patterns and neuromuscular efficiency develop over years of consistent work. Two heavy resistance sessions per week (80–85% of 1RM) yield 2–4% running economy improvement — without adding metabolically expensive muscle mass.
VO₂max declines roughly 1% per year with age — about 10% per decade after age 25–30. Regular training halves that decline rate. An active 55-year-old can have a VO₂max comparable to an untrained 20-year-old. Maximum ventilation drops 6% per decade, diffusion capacity 5% — but the primary cause of VO₂max decline is cardiac and muscular, not pulmonary.
Conclusion: VO₂ Max Is the Start, Not the End
The number everyone obsesses over is the number they can change least. VO₂max is the most visible expression of your genetic ceiling — but it’s not the most controllable component of your performance. Lactate threshold and running economy keep improving for years after VO₂max plateaus. Amateur and elite marathoners run the same streets; the time difference is 100%. Most of that gap is determined not by engine size, but by how much of the engine is usable and how little fuel each step costs.
The coaching frame is this: identify the bottleneck. Low VO₂max — base work and volume. Low threshold — tempo and cruise intervals. Weak economy — high mileage, technique, and resistance work. Frank Shorter won the 1972 Olympic marathon gold with a VO₂max of ~71 ml/kg/min — lower than many of his rivals. The difference was high fractional utilization and superior economy. In Nike’s 2017 Breaking2 Project, carbon-plated Vaporfly shoes improved running economy by about 4% — at Kipchoge’s level, that’s roughly 4 minutes in the marathon. The shoe alone didn’t break the record, but it showed what a 4% marginal gain in one of the three pillars means in the multiplicative total.
Kipchoge’s physiologists noted it quietly: “He was not the biological limit of the human species. He was the current limit.” Know your VO₂max — but don’t make it your only compass. Real performance is born from optimizing all three pillars together.
Related: Can VO₂max Really Be Increased? Related: Insulin Resistance and Exercise Related: Carbohydrate Periodization: Train Low, Compete High
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References
- Hill, A.V. & Lupton, H. (1923). Muscular exercise, lactic acid, and the supply and utilisation of oxygen. Quarterly Journal of Medicine. ↩
- Bassett, D.R. & Howley, E.T. (2000). Limiting factors for maximum oxygen uptake and determinants of endurance performance. Medicine & Science in Sports & Exercise. ↩
- Bouchard, C. et al. (1999). Familial aggregation of VO₂max response to exercise training: results from the HERITAGE Family Study. Journal of Applied Physiology. ↩
- Joyner, M.J. & Coyle, E.F. (2008). Endurance exercise performance: the physiology of champions. The Journal of Physiology. ↩
- McGuire, D.K. et al. (2001). A 30-year follow-up of the Dallas Bed Rest and Training Study. Circulation. ↩
What Is VO₂ Max? — Measuring the Size of the Engine
Maximal oxygen uptake (VO₂max) is the maximum amount of oxygen the body can use during exercise — expressed in milliliters per kilogram per minute (ml/kg/min). The concept dates back to the 1920s, to Nobel-laureate physiologist Archibald Vivian Hill and his colleague Hartley Lupton. Hill described…
What Limits VO₂ Max?
Contrary to common belief, the answer is not the lungs. In healthy individuals, the lungs can load far more oxygen into the blood than the heart can pump. Hemoglobin saturation remains at 95–98% even at VO₂max. Dempsey and colleagues' research has established that the true…
Genetic Ceiling or Training Ceiling?
The HERITAGE Family Study systematically answered this question. 481 adults from 98 sedentary families completed a standardized 20-week aerobic training program. The results were striking: some individuals raised their VO₂max by 50%; others stayed below 5% after the same program [kaynak id="3" author="Bouchard, C. et…
Muscle Fiber Types and the VO₂ Max Relationship
Muscle fiber type distribution is an important determinant of VO₂max potential. Slow-twitch Type I fibers contain more mitochondria, a denser capillary network, and higher oxidative enzyme activity per unit volume — they are more efficient at power generation per unit oxygen and resistant to fatigue.…
Sex Differences and Age Dynamics
Women at similar training levels typically have 15–30% lower VO₂max than men. At elite level the gap narrows to 10–15%. The reasons are physiological: 10–20% lower hemoglobin concentration (less oxygen-carrying capacity), smaller heart volume and cardiac output, higher proportional body fat, and less muscle mass…
