Your VO2 max protocol is based on a house of cards

Mediocre evidence meets extreme confidence

I recently saw a new patient who came in for a preventive evaluation. He’s in his early 40s, very health literate, engaged with his health, and very focused on his longevity protocols.

He boasted to me about how he had dialed in his training. Lifts 3 days a week, gets over 2 hours of zone 2 cardio,¹ and just started the Norwegian 4x4 protocol for VO2 max.

The 4x4 protocol wasn’t something I had much knowledge on, and when I asked him about it, he told me “it’s the scientifically proven best way to raise your VO2 max.”

I wrote in the past about whether getting your VO2 max checked was worthwhile, but I didn’t really touch on any of the data about how to improve that number.

And so after I heard from this patient about the 4x4 protocol, I started to notice it across the longevity world:

• Rhonda Patrick explaining it.

• Dan Go breaking it down.

• Reddit threads debating whether it’s superior to other protocols.

• Women’s Health featuring

• Jessica Biel doing it.

• Men’s Health calling it a game-changer.

• Peter Attia’s detailed protocol breakdown.

It’s pretty wild to me how every longevity influencer is obsessed with VO2 max as the biomarker for cardiovascular fitness and longevity.

And almost all of them are going farther than just saying it matters - they’re prescribing exact protocols to improve it with the confidence of religious doctrine.

But when you actually look at the evidence here, you realize that all of this discourse is based on over extrapolation and low quality data by people who are pretending that they have knowledge they don’t actually possess.

Let’s look at the problems here:

The Foundational Studies Everyone Quotes on VO2 Max Didn’t Measure VO2 Max

The most cited study in the “VO2 max = longevity” literature is the 2018 JAMA paper showing that low cardiorespiratory fitness carries a mortality risk comparable to end-stage renal disease. Peter Attia references it constantly as foundational evidence for why VO2 max is important.

But the study didn’t measure VO2 max and it didn’t even look at regular, healthy people.

This study took people who were referred for a stress test and then measured performance on a Bruce protocol exercise stress test.

There are quite things to note here:

• How long you last on the Bruce protocol is very tightly linked to the effort you put in - you can’t adjust for that in any analysis

• Your exercise capacity on this test is not your VO2 max. Of course, they’re related. But they’re not the same thing - it’s a proxy

• The study didn’t take free-living people and send them for fitness testing. This is a group of people referred for stress test. That’s a very different group of people that folks who are just living their lives and not coming to medical attention

The problems here aren’t unique to this study.

A huge chunk of the “cardiorespiratory fitness” literature uses exercise stress test duration, estimated METs, or other indirect measures.

Then influencers take those findings and make confident claims about VO2 max specifically.

Most of the foundational studies didn’t actually test the thing everyone is now obsessively optimizing for.

Even When We Measure VO2 Max, It’s Messy

A lot of “VO2 max testing” does a poor job of estimating VO2 max.

Familiarity with testing matters. If you rarely run or use a treadmill, your measured VO2 max on a treadmill test will underestimate your true aerobic capacity because you’re mechanically inefficient at the movement. You’re limited by technique, not your cardiovascular system.

Effort during testing matters. VO2 max requires maximal effort. How hard the testers push you, your motivation level, and even whether you’re having a bad day can all impact results substantially.

Protocols vary. Different testing protocols (Bruce treadmill, ramp bike test, etc.) yield different VO2 max values in the same person. We’re talking 5-10% variation or more.

So even if VO2 max is the right metric, we’re measuring it imperfectly with a noisy tool that depends heavily on effort, familiarity, and testing conditions.

The Training Protocols Are Studied Briefly and in Narrow Contexts

The Norwegian 4x4 protocol has been studied. There are actual papers testing it. They’ve even studied something similar in heart failure patients. It isn’t nonsense.

But those studies aren’t testing all of the different protocols and evaluating their impact on both VO2 max and longevity over years.

They are testing these protocols over short durations and comparing the 4x4 protocol to different intervals or steady state activity.

And the studies certainly show that the 4x4 protocol improves markers better than other types of training in some of these studies.

But you need to keep in mind what they don’t show:

• Whether 4x4 is truly the best protocol or if it’s just better than the specific other protocols it’s compared to

• Whether benefit of 4x4 compared to other protocols continues to persist long term or whether it’s attenuated over time

• Anything at all about longevity outcomes

• Whether it’s better than other types of training with equivalent total work

That last point is particularly important - the studies just compare protocols but they don’t adjust for the total work that’s done.

If you don’t control for the intensity/time tradeoff, how can you generalize from that?

Some of the studies will compare the 4x4 protocol to 8x20 seconds or 8x10 seconds intervals or 4x4 at 95% of peak heart rate versus 47 minutes at 70% peak heart rate and then declare the 4x4 more effective.

I can’t find any studies where adjust for total work and then fine tune the protocols to make sure they’re matched up.

As a consequence, none of the comparisons are apples to apples, which truly limit the conclusions you can draw.²

The end result: the data simply doesn’t say what anyone is saying that it does

The house of cards logic to the influencer commentary on VO2 max in general and the 4x4 protocol specifically is fascinating to me.

As Andrew Bubak, PhD says, these influencers are the laziest people in science communication.

The 4x4 protocol is the best way to improve your VO2 max until suddenly someone finds something slightly different in another weak study and that protocol becomes the new hot thing.

That doesn’t mean you should stop doing your “VO2 max” training if you’re enjoying it, but you should know that it’s not what “the science says.”

A lot of the other data on physical activity is equally weak and the assertions are problematic

I don’t want to get too into the weeds on the limitations with what every single “groundbreaking” study says about exercise.

But I do want to draw your attention to one other item that I’ve seen get a lot of attention on social media - the concept of drawing major conclusions about long term exercise based on a 7 day movement sample from a wearable device.

There’s a fascinating piece on Substack from Steve Magness discussing the Twitter argument he got into with Nassim Taleb, the author of The Black Swan and Antifragile, about a study from the UK Bank data:

Nassim Nicholas Taleb@nntaleb

This bro-science retard does not know how to read paper: "At baseline, the mean age of participants was 61.6 years (SD 7.9)". So many people comment without knowing what they are talking about. Increasing survival of senior citizens is NOT increasing athletic performance.

Steve Magness @stevemagness

Taleb is making a big mistake interpreting this paper. This paper doesn’t test zone 1-2 vs. 3-5 or easy vs. intense exercise. It defines vigorous exercise as equivalent to jogging at 15 minute mile pace… For the uninitiated, you can walk at that pace… The actual findings

2:20 PM · Dec 9, 2025 · 284K Views

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77 Replies · 22 Reposts · 504 Likes

If you’re interested in the details of the argument, read the post here.

But this data is just as flawed and useless as all of the VO2 max data I discussed above.

They have people wear an accelerometer for one week, then follow them for years to see who dies or gets sick.

One week of monitoring. And from that single week (during which participants know they’re being monitored and may change their behavior) researchers extrapolate their long-term habitual activity patterns.

How many people do you know whose activity levels in a random week perfectly represented their patterns for the following decade? People change jobs, get injured, have kids, develop new hobbies, go through periods of motivation and burnout.

But we’re supposed to believe one week of data tells us something reliable about long-term movement habits?

Come on.

The Historical Evidence tells us that Simple Activity means Profound Benefits

Here’s what makes the optimization obsession particularly ironic: some of the most compelling evidence for exercise and longevity comes from remarkably simple interventions.

The famous London Transport Workers study from the 1950s found that bus conductors - who simply walked up and down stairs collecting tickets - experienced roughly half the heart attacks and sudden cardiac death compared to sedentary bus drivers. Similar protective effects were seen in postmen compared to desk-bound telephonists and office workers.

These folks weren’t tracking their Zone 2 heart rate or making sure they followed the 4x4 protocol.

They were literally just moving throughout the day - walking rather than sitting. You know, exactly the kind of activity that gets dismissed as “not optimal” in current discourse.

The difference between sedentary and somewhat active appears to matter enormously for disease prevention.

The difference between moderately active and obsessively optimized? Much less clear.

What Actually Matters: Consistency, Adherence, and Psychology

Here’s what too often gets completely lost in this discourse: psychology.

What works for you? What timing of exercise fits into your life? What do you enjoy doing (or what do you hate doing the least)? What do you have access to? What can you can stay consistent with over decades?

Understanding who you are is infinitely more important than following someone else’s “optimal” protocol.

There’s an entire ecosystem of people trying to sell you their protocols, their coaching, their whatever.

But at the end of the day, the biggest determinant of what your health will be like when you’re old isn’t which protocol you chose to maximize your VO2 max.

It’s whether you’re consistently moving or whether you’re always sedentary.

Everyone in this space wants you to follow their advice. They want to steal your attention in exchange for being more confused by their suggestions.

So what you should hear from me is the same thing I tell my patients:

Movement is good. The best type of exercise is the one that you’ll do. People who move tend to feel good. People who don’t move tend to feel old.³

1. "Zone 2" refers to exercise at a low enough intensity that you can sustain it for extended periods - rate of perceived exertion is that you can carry on a conversation, but you don’t want to. The hype in longevity circles is that this is the optimal training to improve mitochondrial function, although that’s starting to be questioned in the wellness world.

2. And this applies to most strength training studies too - short-term studies, small samples, specific interventions, then overly literalized recommendations presented as gospel.

3. And anyone who confidently tells you they know the “science-backed” or “best” way to train is either over-interpreting the evidence, lying to you, or lying to themselves. The evidence for specific protocols being superior to alternatives is weak to nonexistent for long-term health outcomes.