Part of the Longevity Metrics Series: Auditing My Health as I Turn 55

My 55th birthday is June 19th. Every year around my birthday, I audit myself across the health metrics that actually matter. This year I'm going deeper: ten longevity markers, one by one. Grip strength was first. Sleep was second. This week: VO2 max.

I chose this order deliberately. Sleep had to come before everything else because it's foundational to every other metric on this list. But VO2 max has the most striking mortality data of any metric I'll cover. Not slightly stronger. Dramatically stronger.

If there's one number that summarizes how long and how well you're likely to live, VO2 max is probably it.

I'm not going to soften that. The data says what it says. What I want to do is look at it clearly, understand what it means for where I am right now, and figure out what to do with the information. That's the whole point of the audit.

What VO2 Max Actually Is

VO2 max is short for maximal oxygen consumption. It measures the maximum amount of oxygen your body can pull from the air, move through your lungs, pump through your heart, and actually use in your muscles during intense exercise. The unit is milliliters of oxygen per kilogram of body weight per minute (ml/kg/min).

Think of it as a measurement of your entire oxygen delivery chain under maximum demand: lungs, heart, blood vessels, and muscle cells, all working together at their limit. The higher the number, the more efficiently the whole system operates.

It's the gold standard measure of cardiorespiratory fitness, and it's also one of the most actionable numbers in longevity medicine.

The Mortality Data You Need to Know

I want to share this data the way I encountered it: plainly, without drama, because it doesn't need any. It speaks for itself.

Peter Attia's book Outlive was one of the most important things I've read in recent years, and his treatment of VO2 max is where I'd send anyone who wants to go deeper on this. The research he synthesizes is substantial, and this is what it shows.

Moving your VO2 max from the bottom quartile (low fitness) to just below average is associated with a 50 percent reduction in all-cause mortality risk. Moving from low to above average: a 70 percent reduction. When researchers compare people in the lowest fitness category to people at elite fitness levels, the difference in mortality risk over a decade is approximately five-fold.

A 2018 study published in JACC  (Journal of the American College of Cardiology) followed participants for 46 years and found that midlife cardiorespiratory fitness was one of the strongest long-term predictors of survival. Other research shows that each meaningful increase in VO2 max (roughly 3.5 ml/kg/min) is associated with an 11 to 16 percent reduction in cardiovascular and all-cause mortality. One analysis found that each unit increase in VO2 max corresponds to approximately 45 additional days of life expectancy.

To put that in company: VO2 max outperforms smoking, diabetes, high blood pressure, and high cholesterol as a predictor of how long you'll live.

The Study That Changed How I Think About This

In 2018, researchers at UT Southwestern and Texas Health published a randomized controlled trial that I think about often. Dr. Benjamin Levine and his team took 61 healthy but sedentary middle-aged adults between 45 and 64, and put them through a two-year structured exercise protocol: four to five sessions per week, mixing steady moderate-intensity cardio with high-intensity intervals.

The results were remarkable. Participants in the exercise group achieved an 18 percent increase in VO2 max on average. Their left ventricular elasticity, a measure of how well the heart muscle stretches to fill with blood, improved by 25 percent.

They had essentially reversed a meaningful amount of age-related cardiac stiffening. 

The control group, which exercised but avoided sustained aerobic training, showed zero improvement in either measure.

The researchers also identified something they called a window of opportunity. The heart retains enough structural plasticity to remodel itself when training begins in late middle age, ideally before 65. After that, the changes become increasingly fixed.

I'm 55. I'm inside that window. That's not something I read casually and move on from.

What Menopause Does to VO2 Max (and Why Estrogen Matters)

In women, the age-related decline in VO2 max, already roughly 10 percent per decade after age 25, can accelerate significantly after menopause, dropping as much as 12 to 15 percent per decade in sedentary women. Three things are happening at once: estrogen loss accelerates muscle loss, and since muscle tissue is where oxygen gets used, less muscle means lower VO2 max. Estrogen also supports capillary density and vascular function, both of which affect how efficiently oxygen gets delivered. And estrogen has direct cardioprotective effects that, when withdrawn, increase cardiovascular oxidative stress.

Cardiovascular disease is the leading cause of death in women over 60. VO2 max is a stronger predictor of that risk than cholesterol or blood pressure. This connection between hormones and cardiorespiratory capacity is one of the reasons I chose to include estrogen in my HRT protocol. I'll go into the full picture in the Hormones post, which will close out this series. For now, it's worth naming: HRT isn't just about symptoms. It's about protecting the systems that determine how well and how long you function.

The good news is that VO2 max remains highly trainable in women in their 50s, 60s, and beyond. Trained women can cut their rate of decline roughly in half, to about five percent per decade. The intervention isn't complicated. It's consistency.

What a Good Score Looks Like 

The American College of Sports Medicine publishes fitness classifications for VO2 max by age and sex. Here's how the numbers break down across the decades most relevant to this series.

ACSM VO2 Max Norms (ml/kg/min)

Source: American College of Sports Medicine Guidelines for Exercise Testing and Prescription

A few things worth noticing in this table. First, the numbers drop meaningfully with each decade, which is why comparing yourself to age-matched norms matters more than comparing yourself to a generic "good" cutoff. Second, men's values run higher than women's across every category, largely due to differences in hemoglobin concentration, cardiac size, and body composition. Third, even a modest improvement in VO2 max, moving from average to good or good to excellent, represents a significant shift in mortality risk based on the data above.

The Question Isn't Just "Is My Number Good?"

It's "Good Enough for What?"

The ACSM table tells you where you stand relative to people your age. That's useful. But Peter Attia's framing in Outlive pushed me to ask a harder question, and I think it's the one that actually matters.

His argument goes like this: VO2 max declines at roughly ten percent per decade in active adults, and faster if you're sedentary. What this means, practically, is that the fitness you have today is not what you'll have at 80. You're not maintaining a number - you're watching a number fall, and the only question is how fast, and where it lands.

He maps different VO2 levels onto real physical activities. The picture is clarifying. A VO2 max around 35 lets you briskly climb stairs. Around 37, you can jog on flat ground. Below about 18, you can still walk on a level surface, but not much more. That last threshold matters because it's where functional independence starts to slip away.

The framework he proposes is this: if you want a specific physical life at 80, figure out the VO2 max you'll need to support that life, and then work backwards to figure out what you'd need to have now, accounting for two to three decades of decline. Don't target your current age group's "good." Target the elite range for someone two decades younger than you, because that's roughly the cushion that gets you where you want to go.

I'm 55. I want to be hiking at 80. Maybe not the Annapurna Circuit, but real hills. Uneven ground, some elevation, the kind of outing that takes half a day. That hike at 80 probably requires a VO2 max somewhere in the low 30s, minimum. To have a low 30s VO2 max at 80, accounting for ten percent per decade of decline, I'd need to be in the mid-40s now. That's the elite range for my age group, and well above where I currently sit.

This reframes 36, which is my current VO2 max estimate. It puts me solidly in the excellent range for women 50–59. For context, a couple years ago I was tracking around 39 on an Apple Watch. I'm now on an Oura Ring, which estimates VO2 max differently. Oura doesn't run you on a treadmill with a mask. It uses your heart rate response to a brisk walking test combined with your other biometric data to generate an estimate. It's not the same as a lab measurement, it's not the same as the apple watch, and I want to be clear that I am looking at a ballpark number. 

So even though an approximate 36 is a legitimate excellent score for a 55-year-old woman, it’s not where I need to be if I want to be hiking legitimate hills in my eighties. It's a solid starting point, and I want to improve it.

This is exactly what the audit is for. You can't act on information you haven't looked at directly.

How to Actually Improve It

The research points to two distinct levers, and you need both because they do different things.

Zone 2 training is sustained moderate-intensity cardio at roughly 60 to 70 percent of your maximum heart rate. The effort where you can talk, but not comfortably. This builds mitochondrial density, which means more mitochondria per muscle cell, which means more capacity to process oxygen at the cellular level. It's the foundation. Examples include hiking, easy cycling, brisk walking, and easy jogging sustained for 30 to 60 minutes or more.

High-intensity intervals raise the ceiling. The most studied protocol for VO2 max improvement is the Norwegian 4x4: four minutes at 90 to 95 percent of maximum heart rate, followed by three minutes of active recovery, repeated four times. Done two to three times per week, research shows this produces VO2 max improvements of seven to 15 percent over eight to twelve weeks. What it's building is cardiac output and stroke volume, how much blood your heart pumps per beat.

The Levine protocol that reversed cardiac aging in middle age used both. Zone 2 for the base, intervals for the ceiling, four to five days per week, sustained over two years. That's the full picture.

Where I Am and Where I'm Going

I have a strong base. My current training gives me a reasonable version of both levers - Zone 2 and intervals - though not a perfectly structured one.

Krav Maga four times a week for an hour is functionally interval-style training. Hard sessions push me into that 90-plus percent heart rate zone repeatedly, which mirrors the HIIT component of the Levine protocol. The honest nuance is that it's not consistently at that intensity. Some sessions are more technical and less cardiorespiratory. But the structure is there.

Daily walking is my Zone 2 base. 

But 36 is not the number I need for the life I want at 80. I said it above and I mean it: hiking is non-negotiable. Real hills, at 80. Working backwards from that, I need to be moving my VO2 max up, not just maintaining it. That requires adding something I've let drift: running.

I've run before and drifted away from it, and the case for returning is not just about heart rate zones. Running offers something Krav Maga and walking don't, which is sustained impact loading. That's directly relevant for bone health, which I'll cover in a later post. It also recruits muscles differently and adds a reliable cardiorespiratory ceiling that I can track consistently. For someone trying to build toward the mid-40s VO2 range, it's not optional, it's strategic, especially if I add 4x4 minute sprinting intervals.

The truth is, I don't love running in New York City. Pavement is harder on the body, and I have real concerns about air quality. My solution: I'm committing to getting to Central Park's trails at least once a week. Soft ground, better air quality. It's a small logistical lift for a meaningful difference.

The Summary

VO2 max is the single most powerful predictor of how long and how well you'll live. The mortality data is not ambiguous. The good news is that it responds to training, it remains trainable well into midlife and beyond, and the window for meaningful cardiac remodeling is still open at 55.

The audit continues.

Want to build a protocol around your own numbers? My concierge coaching program is built around you specifically: your data, your history, your goals. If working through your own audit sounds like what you need, that's the work we do together. Learn more here.

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