Can You Improve VO₂ Max by Walking? What the Research Says

I have a friend who hates running. Genuinely, deeply dislikes it. But after reading about how VO₂ max predicts longevity better than almost any other health metric, she wanted to know: can I actually improve this number without running? Can I just... walk?

I told her what I'd heard in the fitness world: walking is great for general health, but if you want to move your VO₂ max, you need intensity. Zone 4 intervals. The Norwegian 4×4 protocol. Real cardiovascular stress.

Then I looked at the research more carefully. And the answer turned out to be more interesting than the blanket dismissal I'd been repeating.

The short answer: it depends on where you're starting

Walking can improve your VO₂ max. But the size of the effect depends almost entirely on one variable: your current fitness level.

A meta-analysis of 41 controlled trials involving over 2,100 sedentary older adults found that endurance exercise training produced an average VO₂ max improvement of 3.78 mL/kg/min, roughly a 16% increase. Most of the studies in that analysis used walking as the primary form of exercise. The sessions were typically 30 to 40 minutes, three times per week, at moderate intensity. And the improvements were real and statistically significant.

What struck me was the subgroup analysis: the greatest gains came from programs lasting more than 20 weeks at an intensity of about 60 to 65% of VO₂ max. That's brisk walking territory for most sedentary adults. Not jogging. Not intervals. Walking with purpose.

Another study put sedentary women aged 22 to 40 through a 40-week treadmill walking program at about 72% of max heart rate. Their VO₂ max improved by 22%. Most of that improvement happened in the first 20 weeks, then plateaued. That's a substantial gain from an activity most people wouldn't consider "real" cardio training.

And a study on sedentary adults aged 60 to 71 who trained primarily by walking and running over 9 to 12 months found an average VO₂ max improvement of 24%, with a range from 0 to 58%. The improvement didn't differ significantly between men and women, or between the youngest and oldest participants.

The pattern is clear: if you're starting from a low baseline, walking works. It works well.

Why walking stops working (and when)

Here's the part that matters for people who are already somewhat active.

The stimulus for VO₂ max improvement requires challenging your cardiovascular system beyond what it can comfortably handle. For a sedentary person with a VO₂ max of 25, a brisk 40-minute walk absolutely does that. Their heart rate climbs to 65 to 75% of max. Their breathing quickens. Their muscles demand more oxygen than they're used to delivering. The body adapts.

But for a 35-year-old who already runs a few times a week and sits at a VO₂ max of 42? Walking doesn't create enough cardiovascular stress to force further adaptation. You'd be well below Zone 2, barely tickling the aerobic system. Your heart rate might stay under 55% of max. That's not a training stimulus. It's transportation.

This is why the research findings seem contradictory at first glance. Walking produced a 22% VO₂ max improvement in one study and virtually nothing in another. The difference wasn't the walking. It was the starting fitness of the subjects.

An overview of systematic reviews examining exercise training intensity and VO₂ max concluded that both low-intensity and high-intensity training improve VO₂ max in sedentary adults. But when the researchers compared low-intensity protocols to high-intensity ones directly, the differences were either small, trivial, or inconclusive. In other words, for unfit populations, the intensity matters less than simply showing up consistently.

For already-fit populations, the picture changes. That's where the 4×4 intervals and Zone 4 training become necessary. The cardiovascular system needs a stronger signal to keep adapting.

The hidden advantage: walking is the exercise you'll actually do

Here's something the VO₂ max optimization crowd often overlooks. The best training protocol is the one you stick with.

Research on exercise adherence paints a sobering picture. Roughly half of people who start an aerobic exercise program drop out within six months. The dropout rate for high-intensity training is even higher than for moderate-intensity work, for obvious reasons: it's uncomfortable, it's intimidating, and it requires a level of commitment that many people aren't ready for.

Walking sidesteps most of those barriers. It doesn't require special equipment. It doesn't leave you gasping. You can do it while listening to a podcast that holds your attention. The internal negotiation that makes hard intervals feel impossible simply doesn't happen at walking intensity.

And here's the longevity math that convinced me walking deserves more respect: a single MET increase in exercise capacity (about 3.5 mL/kg/min of VO₂ max) is associated with a 10 to 25% improvement in survival odds. If a sedentary person improves their VO₂ max by 3 to 4 mL/kg/min through consistent walking, that's a clinically meaningful shift. It doesn't matter that it came from walking instead of sprinting. The cardiovascular system doesn't care about the source of the stimulus. It cares about the adaptation.

How to actually make walking improve your VO₂ max

If you're starting from a sedentary baseline and want to use walking as your primary tool, the research suggests a few things.

Walk briskly, not casually. A stroll through the park at 2 mph probably won't challenge your cardiovascular system enough. Brisk walking at 3.5 to 4.5 mph, the kind where you're breathing noticeably harder and holding a conversation takes slightly more effort, is where the research shows consistent benefits. A randomized controlled study of 119 middle-aged adults found significant VO₂ max improvements from walking at 65 to 75% of VO₂ max, 50 minutes per session, four times per week.

Use terrain to your advantage. Hills naturally increase the cardiovascular demand of walking without requiring you to move faster. Your heart rate climbs. Your muscles work harder. For people who can't or won't run, incline walking on a treadmill or hilly outdoor routes is one of the most effective ways to push walking intensity into a zone that drives adaptation. Just note that your Apple Watch may not record a VO₂ max reading on very steep terrain, since it prefers grades under 5%.

Be consistent for longer than you think. The meta-analysis on older adults found greater improvements with programs lasting more than 20 weeks. Walking adaptations are real but slow. You're building the same cardiovascular infrastructure as any other endurance training: stronger heart chambers, more capillaries, increased blood volume. These are biological construction projects that take months, not weeks.

Track your heart rate. If your brisk walk keeps your heart rate in the 60 to 75% range of your max, you're in productive territory. Below 60%, the stimulus is probably too light. If you're a 50-year-old, that means keeping your heart rate roughly between 105 and 130 bpm during your walks. A watch or chest strap makes this easy to monitor.

The Apple Watch connection

Here's something I find interesting: the Apple Watch estimates your VO₂ max specifically from outdoor walks, runs, and hikes. Walking is literally one of the three activities the algorithm uses to assess your cardiovascular fitness. According to Apple's documentation, the watch correlates your heart rate with your pace during these activities to generate an estimate.

This means that as your walking fitness improves, your Apple Watch should eventually reflect that. If your heart rate at the same walking pace drops over time, the algorithm interprets that as improved cardiovascular efficiency and adjusts your reading upward. It's one of the more elegant feedback loops in consumer fitness tracking.

That said, the watch needs certain conditions to generate a reading: outdoor GPS signal, a heart rate elevation of at least 30% above resting, and relatively flat terrain. Casual walks may not always trigger an update. Brisk, purposeful walks are more likely to produce data.

When to graduate from walking

If walking improves your VO₂ max from, say, 25 to 32 mL/kg/min, that's fantastic. You've meaningfully reduced your mortality risk and built a real aerobic base. But at some point, walking stops providing enough stimulus to push further.

That's the moment to consider adding some running intervals or other higher-intensity work. Not because walking failed. Because it succeeded. It brought you to a fitness level where your body now needs a louder signal.

The 80/20 polarized model is designed exactly for this progression. You could transition to a week where four walks stay easy (still building your base, still contributing to recovery) and one session introduces short running intervals at higher intensity. The walking doesn't disappear. It becomes the foundation that the harder work builds on.

For a 40-year-old female currently at a VO₂ max of 30, the path from 30 to 36 might be entirely walkable. The path from 36 to 42 likely requires more intensity. Knowing which phase you're in, and what kind of effort each phase demands, is what makes training efficient rather than frustrating.

The real takeaway

Walking is dramatically underrated as a VO₂ max tool for people who need it most. The research consistently shows that sedentary and low-fitness individuals can achieve meaningful, measurable cardiovascular improvements from brisk walking programs lasting several months.

The people who benefit most are also the people least likely to start with high-intensity intervals. And the longevity data doesn't distinguish between how you improved your fitness. It just cares that you did. Every point of VO₂ max gained carries the same mortality benefit whether it came from a 4×4 interval or a 45-minute walk through your neighborhood.

My friend started walking four times a week, 40 minutes at a brisk pace, on routes with a few hills. After three months, her Apple Watch showed her VO₂ max had climbed by about 3 points. Not dramatic. Not Instagram-worthy. But based on the Cleveland Clinic mortality data, potentially one of the most important things she did that year.

The best exercise for longevity is the one that gets you from the couch to something better. For a lot of people, that something is a walk.

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Track your VO₂ max progress over time with VO2 Max Pro. The app syncs with Apple Health, notifies you when your Apple Watch records new readings from walks, runs, or hikes, and translates your number into a biological age so you can see what your cardiovascular fitness actually means.