What is VO2 max and how to improve it for runners

Photo by VO2 Master on Pexels

If you’ve ever glanced at your watch after a run and seen a VO2 max number staring back at you, you’ve probably wondered whether it actually matters — or whether it’s just another metric designed to make you feel like you’re not doing enough. It’s a fair question. Half the running world seems obsessed with this number, and the other half has no idea what it means beyond “higher is better.”

Here’s the honest version: VO2 max is a genuinely useful measure of your aerobic fitness, but it’s not the be-all and end-all your watch app makes it out to be. It won’t tell you how to pace a race, it can’t account for grit or fuelling or how you slept, and chasing the number for its own sake is a good way to overtrain and under-recover. Used properly, though, understanding it can sharpen your training and explain why some sessions matter more than others.

This article breaks down what VO2 max actually is, what a “good” number looks like for real (non-elite) runners, and — more usefully — exactly which sessions improve it, how often to do them, and how long it realistically takes to see change.

What VO2 max actually measures

VO2 max is the maximum rate at which your body can take in, transport, and use oxygen during intense exercise. It’s measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). The higher the number, the more oxygen your muscles can use to produce energy — which, in theory, means you can sustain faster paces before you’re relying on less efficient, more fatiguing energy systems.

It was originally measured in exercise physiology labs using a treadmill, a mask, and a gradually increasing workload until you couldn’t continue. That’s still the gold standard. What your Garmin or Coros gives you is an estimate, based on your pace, heart rate, and heart rate variability during runs — and it can be off by several points in either direction. Don’t treat the number on your wrist as gospel. Treat it as a rough trend line.

According to the American College of Sports Medicine, VO2 max is one of the strongest predictors of cardiovascular fitness and long-term health, not just running performance — which is one reason it’s worth caring about even if you’re not chasing a PB.

Why it matters for everyday runners

VO2 max correlates with how fast you can run for a sustained period, but it’s not the only factor. Two runners with identical VO2 max scores can have very different race times because of differences in running economy (how efficiently you use that oxygen), lactate threshold, and mental pacing.

What VO2 max is genuinely good for:

• Tracking whether your aerobic fitness is trending up or plateauing over months
• Understanding why certain training sessions (intervals, hills) feel so much harder than easy runs
• Getting a rough, non-diagnostic sense of cardiovascular health

What it’s not good for:

• Predicting your exact race time
• Comparing yourself to other runners with different training histories
• Deciding you need to “fix” it every single week

What’s a “normal” VO2 max for real runners

Elite marathoners often sit in the 70–85 ml/kg/min range. That’s not the comparison you should be making. Here’s a more realistic breakdown for recreational runners, based on data ranges commonly cited by sports science bodies and watch manufacturers:

These are broad ranges, not targets to hit by a deadline. Age, sex, genetics, and years of training all shift where you naturally sit. A 45-year-old who took up running two years ago and a 22-year-old former college athlete will have very different starting points — and that’s fine.

The sessions that actually improve VO2 max

This is where most articles get vague. Here’s what the research and coaching consensus actually says works.

VO2 max intervals — these are the most direct stimulus. Think 3–5 minute efforts at roughly 95–100% of your current 5K effort, with equal or slightly shorter recovery jogs. For example: 5 x 4 minutes hard, 3 minutes easy jog between. This is uncomfortable — you should be breathing hard by the second minute of each rep.

Shorter, harder intervals — 30/30s or 1-minute-on/1-minute-off at close to mile pace also drive VO2 max adaptations, and they’re often more approachable for runners newer to structured speed work because the discomfort comes in shorter bursts.

Hill repeats — running hard uphill for 60–90 seconds forces your cardiovascular system to work at a high intensity while reducing impact stress compared to flat sprinting. If you want session ideas, our guide to hill training for runners covers specific workouts that double as VO2 max stimulus.

Consistent aerobic base mileage — this doesn’t directly spike VO2 max the way intervals do, but it builds the capillary density and mitochondrial efficiency that make your hard sessions actually productive. Skipping this and going straight to intervals is like trying to build a house without foundations. If you’re not sure what base building looks like in practice, it’s worth reading about base building for runners before you load up on speed work.

Here’s a simple weekly structure for a runner training 4 days a week who wants to prioritise VO2 max without burning out:

How long it actually takes to see change

This is the part people don’t want to hear: VO2 max doesn’t move quickly, and it doesn’t move linearly. Most studies looking at structured interval training show measurable improvements (typically 5–15%) over 6–12 weeks of consistent training — but that’s with sessions done properly, roughly once or twice a week, alongside adequate recovery.

If you’re newer to running, your VO2 max will likely rise faster in your first year simply because your whole aerobic system is developing from a lower base. If you’ve been running consistently for 3+ years, gains will be smaller and slower — a point that Runner’s World has covered extensively when discussing training plateaus in experienced runners.

Don’t expect your watch to show a new number every week. It updates based on trends across multiple runs, and short-term fluctuations (a hot day, poor sleep, a stressful week) can nudge it down temporarily without meaning anything has gone backwards.

Why chasing the number can backfire

Because VO2 max intervals are genuinely hard, it’s tempting to do more of them, more often, believing that’s the fastest route to a higher number. It isn’t. Doing hard interval sessions more than twice a week, without enough easy running in between, is one of the more common paths to burnout, elevated resting heart rate, and injury — particularly for runners still building their weekly mileage base.

Your heart rate zones matter here more than people realise, because running your “easy” days too hard is one of the sneakiest ways to blunt VO2 max gains — you end up too fatigued to hit the intervals properly. If you’re not confident on what easy actually feels like, our breakdown of heart rate zones for running is worth ten minutes of your time.

For runners training around a job, kids, or unpredictable schedules — which is most of us — one quality VO2 max session a week, done consistently for 8–10 weeks, will do more than three sloppy ones squeezed in when you’re already tired.

The Honest Takeaway

• VO2 max is a useful trend indicator of aerobic fitness, not a precise predictor of race performance — don’t let a watch number dictate your mood about a run.
• One structured VO2 max session per week (3–5 minute hard efforts, or 30/30s) is enough for most recreational runners to see gains over 8–12 weeks.
• Improvements need an aerobic base underneath them — easy runs and consistent weekly mileage matter as much as the hard sessions.
• Expect gains of roughly 5–15% over a few months with consistent training, and expect that progress to slow the longer you’ve been running.
• If your VO2 max estimate stalls or dips for a week or two, check your sleep, stress, and recovery before assuming your fitness has actually declined.

Next read: How to build a running training plan from scratch