How do you improve your VO2max as an endurance athlete?

What is VO2max and why does it matter?

VO2max is the maximum volume of oxygen your body can take in, transport, and use per minute during intense exercise. It's expressed in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). A sedentary 40-year-old man might sit around 30 ml/kg/min. A fit amateur runner: 50–60. A professional cyclist or marathon runner: 70–85. Kilian Jornet has been tested above 90.

It matters for two separate reasons. In sport, VO2max is the physiological ceiling on how hard you can go for any sustained effort — a higher VO2max means a higher ceiling, more room for everything below it, and more absolute horsepower. Outside of sport, VO2max is one of the strongest single predictors of long-term health outcomes. Large longitudinal studies consistently show that people in the top cardiorespiratory fitness quintile live longer and have dramatically lower risk of cardiovascular disease, certain cancers, and all-cause mortality than those in the bottom quintile. The health upside alone is worth training for.

Is VO2max genetic or trainable?

Both — and the split is more favorable than most people think. Twin studies and large training cohorts suggest that roughly 50% of VO2max is genetically determined and 50% is trainable. The genetic share sets the maximum ceiling you could ever reach with perfect training; the trainable share is the part you actually control.

For a previously sedentary adult, a well-designed first training block can raise VO2max by 15–25% in three to six months — a genuinely life-changing delta. For a trained athlete, gains are smaller but meaningful: 5–10% over a focused block is a strong result. At the elite level, single-digit-percent gains over a full season are what separates world-class from great. The curve flattens with training age, but it never flattens to zero.

What workouts actually raise VO2max?

The principle is simple: to raise VO2max, you have to spend meaningful time at or very close to it. That means intensities of about 90–100% of VO2max power or pace — essentially what you could hold for somewhere between 6 and 12 minutes if you went all out. In Coggan-zone terms, this is zone 5 (106–120% of FTP). In running, it's roughly your current 5-kilometre pace, or a touch faster.

Because you can only sustain that intensity for a few minutes before your legs give out, VO2max work is almost always done as intervals. A handful of protocols have decades of evidence and continuous pro-level use behind them.

The Norwegian 4×4

The most studied VO2max protocol in the world. Four intervals of four minutes at the hardest pace you can hold evenly for the full block (around 90–95% of max heart rate), separated by three minutes of easy active recovery. Research out of Norway's NTNU group has shown it reliably lifts VO2max even in previously sedentary adults.

It hurts. It's supposed to. The four-minute duration is the sweet spot: long enough that you reach VO2max inside the interval, short enough that you can repeat it four times.

Session length: ~40 minutes including warm-up and cool-down. Frequency: 1–2 per week. Great for runners, cyclists, and time-crunched athletes.

30/30 intervals

Popularized in cycling by Billat's research and later by Tour de France physiologists. The pattern: 30 seconds hard (around 105–115% of FTP or roughly 3K race pace), 30 seconds easy, repeated for 10 to 20 minutes per set. Do one to three sets with 5 minutes easy between them.

The mechanism is elegant: the short recoveries never let your oxygen consumption drop, so you accumulate a very large total time spent at or near VO2max across the whole block — often more than you'd reach in a 4×4. They're also psychologically easier than 4×4s because no single effort feels desperate.

Session length: 45–70 minutes. Frequency: 1–2 per week. Excellent for cyclists, increasingly used by runners on the track.

5×3 and 3×5 classic sets

Five three-minute intervals with two to three minutes of recovery, or three five-minute intervals with three to four minutes of recovery. Slightly longer intervals than a 4×4 means slightly lower intensity — typically around 110% of FTP — with more total time at the target zone. Both are staples in classical interval training and used across cycling, running, and rowing.

Session length: 50–70 minutes. Frequency: 1–2 per week. Good variation when you want to avoid protocol monotony.

Why Zone 2 work still matters when you're chasing VO2max

The most common mistake athletes make when they decide to train VO2max is ditching their easy miles and going hard every session. It's the fastest way to plateau or injure yourself.

The reason is physiological. The adaptations from Zone 2 work — mitochondrial density, capillarization, fat oxidation capacity, and a robust aerobic base — are precisely what let you tolerate and recover from the hard VO2max intervals. Athletes with a deep Zone 2 base can absorb two hard VO2max sessions a week. Athletes with no base can barely handle one before fatigue breaks the block.

The modern consensus, sometimes labeled polarized training, is roughly 80% of weekly time at low intensity and 20% at moderate-to-high intensity. That's where VO2max gains live.

How long until you see VO2max gains?

A beginner following a structured plan with two VO2max sessions per week on top of Zone 2 can see meaningful change within 4 to 6 weeks and strong change within 12. For trained athletes, the honest timeline is 6 to 12 weeks of dedicated focus for a visible improvement, with the gains holding as long as you keep touching the intensity at least once a week.

One crucial detail: VO2max gains are perishable. Stop doing interval work for more than three or four weeks and you'll start sliding back. The whole point of polarized training is that you keep the intensity in the plan year-round in small doses, not that you blast it for six weeks and abandon it.

What are the common mistakes with VO2max training?

Four mistakes catch almost every athlete who decides to get serious about VO2max.

• Going too hard on the first interval. If you blow yourself up in the first four minutes, every subsequent interval drops below the VO2max zone and the session becomes a hard threshold ride. Pace the set so the last interval is the hardest, not the first.
• Skipping Zone 2. VO2max sessions are the cherry, not the cake. Without a base underneath, the adaptation stalls and you break down.
• Doing VO2max every single session. Two quality sessions a week is the ceiling for most athletes. More than that and you're training your fatigue, not your fitness.
• Trusting wrist-based VO2max estimates as training feedback. Apple Watch and Garmin estimates are directionally useful, often within 10–15% of a lab value, but they are not sensitive enough to reflect a single good block of training. Judge your progress by interval power or pace, not by the number on your wrist.

Does VO2max training look different for runners and cyclists?

The principles are identical. The execution differs in two practical ways.

Running VO2max intervals are more orthopedically expensive than cycling because of the impact load. Most runners cap hard interval work at two sessions per week and need more recovery between them. Cyclists, with no impact, can sometimes handle three quality sessions per week during a focused block, though two is still the safer default.

Cycling VO2max sessions are easiest to control indoors on a smart trainer — the resistance is constant, the power is precise, and nothing tempts you to turn a recovery into a race. Running VO2max sessions live on a flat track, a treadmill, or a consistent grass loop. The shared rule is the same: the goal is to hit the target intensity cleanly, not to produce a hero effort once.