"People who move tend to feel good. People who don’t move tend to feel old." So true. At 80 I do something almost every day. Usually strength training 3 days, swimming 2 or 3 and walking one. I don't feel old. Most of my friends in their 70s or 80s do nothing and complain about how bad they feel. Longevity is pointless if you're miserable. Do something!
I was a competitive runner in my younger years (lol), but not so much anymore. Its always comical to me when I hear VO2 studies. That is because when I usually are seeing VO2 measured in papers its in the context of running. However, this as you stated underestimates your cardiovascular fitness if your not a runner. For example, I have two sons who participate in endurance sports. One runs cross country in middle school and who is reasonably fast. My other son swims competitively and is very good at all the distance events. However, place my son who runs in the pool and he struggles to complete multiple laps without stopping. Now place my other son on the track and its comical (maybe I shouldn't chuckle but I do) to watch him labor to run a mile. Therefore, I'm sure if you were studying V02 max in him he would likely not grade well as my other son who runs consistently However, as you mentioned that's not a true apples to apples compassion. I would also agree in that consistently moving for most Americans should be the ultimate goal as this is to often overlooked.
In addition to all the great points you make here, we must also understand that the data being quoted by these wellness influencers all comes from observational studies. They show associations of VO2max with all-cause mortality. They don't prove that increasing your VO2max lowers your mortality rate. Attia, who is appropriately and vehemently dismissive of observational nutritional studies has written an entire article entitled "The [almost] unbelievable effects of a high maximal aerobic capacity on all-cause mortality" which also conflates association with causality.
Thank you for the meticulous look at this particular optimization obsession. Another concern about the Bruce protocol – one that applies even to runners – is that it folds in assumptions about how long it takes a person to "warm up". I can run a full marathon with an average pace below Stage 7, but I can't reach that stage in the protocol because I need more time to get up to speed. I don't know how broadly this limits the validity of the protocol, but at least for me it couldn't possibly measure my V02 max accurately.
This is such a needed dose of epistemic humility in the “VO₂ max as religion” era.
As a physician-scientist, I loved the way you separate three different claims that get bundled together online:
1. VO₂ max is strongly associated with outcomes (true, broadly).
2. Therefore, any protocol that raises VO₂ max is “longevity proven” (not established).
3. And specifically the Norwegian 4×4 is the scientifically proven best method (way too confident for the underlying evidence base). 
Your critique lands because it’s not anti-intervals, but it’s anti–surrogate worship. In real clinical decision-making, we’d never accept “this moves a surrogate in small, selected studies” as equivalent to “this is the optimal intervention for everyone’s long-term health,” especially when we’re ignoring dose, injury risk, adherence, and the fact that most of the healthspan benefit probably comes from consistent volume and overall cardiorespiratory fitness, not from any single branded interval recipe. 
Also appreciated the quieter point: people are often chasing an exact VO₂ number with extreme confidence, while their measurement tool (wearable estimate or even a single lab test) is noisy and context-sensitive. The better target is durable capacity: can you do more work, recover better, and stack months/years of training without breaking? That’s the physiology that actually compounds.
You have hit on what I call “ass out the door “. Motion is the lotion for a better quality of life. I do 4x4 intervals to help me in my cycling…especially mountain biking. I have seen improvement in my performance from the interval training as well as zone 2 training (pain cave to boring). Will I live longer because of it? IDK. It is hard to know who and what to believe without becoming the expert yourself. I appreciate the light you shine on these issues and your use of citations to support or refute them.
Great breakdown of the data. Totally agree that the influencers go a bit (understatement??!?) overboard.
That said - I volunteer at a university wellness center that conducts VO2 tests and iDXA scans and am impressed by the impact folks like Peter Attia are having on getting folk to take an outsized interest in their health. Even with the biased and even extreme extrapolated nature of their analysis (or even because of) - they are having a net positive effect.
Every client in my short tenure has cited Attia as the reason they were there. Love this analysis’ focus on encouraging them to do better (and am disappointed ,as other posters note, about Peter’s lack of integrity here - since that is such a focus of his elsewhere), but also recognize that at least this hype cycle appears to be having some positive effect.
Good points. House, Johnston, and Jornet in Training for the Uphill Athlete, an excellent book, have some choice words to say about VO2 max, based on their years of coaching and training: "VO2 max has become the standard metric for measuring cardiovascular fitness because it is easily measured and can be compared across the test subjects as well as across populations—not because it is the best predictor of endurance. The unintended consequence of this has been to make VO2 max synonymous with endurance in the minds of the lay public."
"Long-term studies, along with personal testing by author Johnston, have demonstrated that elite endurance athletes will often show no change (and even a reduction) in VO2 max during a competition season and over their careers while at the same time seeing marked improvements in performance. These gains in performance come from improved economy and speed at the lactate threshold (the other two legs of the endurance tripod). VO2 max is what is called a 'first wave response' to training. This term refers to a quality that tends to develop quickly in the young and those new to endurance training."
So Dr Katz, based on your review of the literature, what do you do for exercise/cardio? Agree a lot of the claims seem based on fuzzy research. Average VO2 data by age seem especially suspect. Thanks for the post.
I do a mix of weights and aerobic exercise. But I’m weird because I’ve always loved being in the gym and so I recognize my preferences are not universal. I will post about the specifics of my own exercise routine and rationale behind it at some point
Thank you for breaking down this fad, and providing the much needed context for VO2 max studies. I subscribe to the "a little bit of activity goes a long way" and "use it or lose it" philosophies. They are obviously not money-making protocols.
I just love good old common sense. Thank you for pointing this out doctor. Now, over at my blog, I have this “Common Sense” protocol I’m selling for just $7.99…
"People who move tend to feel good. People who don’t move tend to feel old." So true. At 80 I do something almost every day. Usually strength training 3 days, swimming 2 or 3 and walking one. I don't feel old. Most of my friends in their 70s or 80s do nothing and complain about how bad they feel. Longevity is pointless if you're miserable. Do something!
I was a competitive runner in my younger years (lol), but not so much anymore. Its always comical to me when I hear VO2 studies. That is because when I usually are seeing VO2 measured in papers its in the context of running. However, this as you stated underestimates your cardiovascular fitness if your not a runner. For example, I have two sons who participate in endurance sports. One runs cross country in middle school and who is reasonably fast. My other son swims competitively and is very good at all the distance events. However, place my son who runs in the pool and he struggles to complete multiple laps without stopping. Now place my other son on the track and its comical (maybe I shouldn't chuckle but I do) to watch him labor to run a mile. Therefore, I'm sure if you were studying V02 max in him he would likely not grade well as my other son who runs consistently However, as you mentioned that's not a true apples to apples compassion. I would also agree in that consistently moving for most Americans should be the ultimate goal as this is to often overlooked.
In addition to all the great points you make here, we must also understand that the data being quoted by these wellness influencers all comes from observational studies. They show associations of VO2max with all-cause mortality. They don't prove that increasing your VO2max lowers your mortality rate. Attia, who is appropriately and vehemently dismissive of observational nutritional studies has written an entire article entitled "The [almost] unbelievable effects of a high maximal aerobic capacity on all-cause mortality" which also conflates association with causality.
Fully agree. The willingness to extrapolate and pretend that there is true rigor is wild to me
Thank you for the meticulous look at this particular optimization obsession. Another concern about the Bruce protocol – one that applies even to runners – is that it folds in assumptions about how long it takes a person to "warm up". I can run a full marathon with an average pace below Stage 7, but I can't reach that stage in the protocol because I need more time to get up to speed. I don't know how broadly this limits the validity of the protocol, but at least for me it couldn't possibly measure my V02 max accurately.
Completely concur
This is such a needed dose of epistemic humility in the “VO₂ max as religion” era.
As a physician-scientist, I loved the way you separate three different claims that get bundled together online:
1. VO₂ max is strongly associated with outcomes (true, broadly).
2. Therefore, any protocol that raises VO₂ max is “longevity proven” (not established).
3. And specifically the Norwegian 4×4 is the scientifically proven best method (way too confident for the underlying evidence base). 
Your critique lands because it’s not anti-intervals, but it’s anti–surrogate worship. In real clinical decision-making, we’d never accept “this moves a surrogate in small, selected studies” as equivalent to “this is the optimal intervention for everyone’s long-term health,” especially when we’re ignoring dose, injury risk, adherence, and the fact that most of the healthspan benefit probably comes from consistent volume and overall cardiorespiratory fitness, not from any single branded interval recipe. 
Also appreciated the quieter point: people are often chasing an exact VO₂ number with extreme confidence, while their measurement tool (wearable estimate or even a single lab test) is noisy and context-sensitive. The better target is durable capacity: can you do more work, recover better, and stack months/years of training without breaking? That’s the physiology that actually compounds.
Thank you for reading
You have hit on what I call “ass out the door “. Motion is the lotion for a better quality of life. I do 4x4 intervals to help me in my cycling…especially mountain biking. I have seen improvement in my performance from the interval training as well as zone 2 training (pain cave to boring). Will I live longer because of it? IDK. It is hard to know who and what to believe without becoming the expert yourself. I appreciate the light you shine on these issues and your use of citations to support or refute them.
Thanks for the logical discussion of all of these “influencers.”
Great read. Great points. “What do you hate doing the least “– on point. Thanks for your time.
For most people, “what do you hate doing the least” is the most important activity question to answer
Great breakdown of the data. Totally agree that the influencers go a bit (understatement??!?) overboard.
That said - I volunteer at a university wellness center that conducts VO2 tests and iDXA scans and am impressed by the impact folks like Peter Attia are having on getting folk to take an outsized interest in their health. Even with the biased and even extreme extrapolated nature of their analysis (or even because of) - they are having a net positive effect.
Every client in my short tenure has cited Attia as the reason they were there. Love this analysis’ focus on encouraging them to do better (and am disappointed ,as other posters note, about Peter’s lack of integrity here - since that is such a focus of his elsewhere), but also recognize that at least this hype cycle appears to be having some positive effect.
Thank you @gregorykatz for a well written post.
I’ve had a lot of patients who come to see me because they read Attia’s book
Good points. House, Johnston, and Jornet in Training for the Uphill Athlete, an excellent book, have some choice words to say about VO2 max, based on their years of coaching and training: "VO2 max has become the standard metric for measuring cardiovascular fitness because it is easily measured and can be compared across the test subjects as well as across populations—not because it is the best predictor of endurance. The unintended consequence of this has been to make VO2 max synonymous with endurance in the minds of the lay public."
"Long-term studies, along with personal testing by author Johnston, have demonstrated that elite endurance athletes will often show no change (and even a reduction) in VO2 max during a competition season and over their careers while at the same time seeing marked improvements in performance. These gains in performance come from improved economy and speed at the lactate threshold (the other two legs of the endurance tripod). VO2 max is what is called a 'first wave response' to training. This term refers to a quality that tends to develop quickly in the young and those new to endurance training."
Today’s health influencers are too often snake oil sales people and whatever a great many say needs to taken with a grain or more of salt.
Thank you!
When influencer "noise" sucks up all the oxygen in the room, Methods are relegated to secondary audiences.
Their stress test cohort front loads for deltas.
I enjoy exercising but if I had a specific protocol to follow I’d loose the enjoyment. Lots of variety and small personal goals keep me moving.
Personal preference matters more than anything else
So Dr Katz, based on your review of the literature, what do you do for exercise/cardio? Agree a lot of the claims seem based on fuzzy research. Average VO2 data by age seem especially suspect. Thanks for the post.
I do a mix of weights and aerobic exercise. But I’m weird because I’ve always loved being in the gym and so I recognize my preferences are not universal. I will post about the specifics of my own exercise routine and rationale behind it at some point
Thank you for breaking down this fad, and providing the much needed context for VO2 max studies. I subscribe to the "a little bit of activity goes a long way" and "use it or lose it" philosophies. They are obviously not money-making protocols.
I tell patients “use it or lose it” all the time
I just love good old common sense. Thank you for pointing this out doctor. Now, over at my blog, I have this “Common Sense” protocol I’m selling for just $7.99…