If You've Ever Wondered Whether Your Cardio Is Actually Working — This Test Tells You

Most business leaders who exercise consistently have absolutely no idea whether their training is actually improving their cardiovascular fitness. They feel better. They track their steps. They get their heart rate up. But they don't know their number. And there is a number that matters more than almost any other health metric you're probably tracking.

That number is VO2 max. And if you don't know yours, you're operating blind on one of the most powerful longevity levers in medicine.

What VO2 Max Actually Is — and Why It Matters More Than You Think

VO2 max is the maximum volume of oxygen your body can absorb and use during intense exercise. Think of it as your cardiovascular engine capacity — the ceiling of what your aerobic system can deliver under pressure. And it turns out that number is the single strongest predictor of all-cause mortality we have in medicine.

Not cholesterol. Not blood pressure. Not fasting glucose. VO2 max.

A landmark study of 750,000 people found that low cardiorespiratory fitness was the most powerful predictor of early death — more than smoking, more than diabetes, more than hypertension. Let that sink in. Your cardiovascular fitness level is a bigger mortality risk factor than whether you smoke.

Every 3.5 ml/kg/min increase in VO2 max is associated with a 13% reduction in all-cause mortality risk. That is not a soft, feel-good metric. That is a longevity lever you should be actively pulling.

The Problem with How You're Currently Measuring This

Here's the issue. Most people have never had their VO2 max clinically tested. They rely on what their Apple Watch gives them — which is an algorithm-based, non-accurate estimate. The watch is looking at your resting heart rate, your heart rate during activity, maybe your age and weight, and running it through a model. It's a guess.

Clinical VO2 max testing is something different entirely. You wear a mask. You're on a treadmill, an air dyne, or an exercise bike. The protocol pushes you progressively harder until you hit your actual physiological maximum. The equipment measures the precise volume of oxygen you're taking in and the carbon dioxide you're producing. The result is a precise number — not an estimate, not a trend, not a "good" or "excellent" badge from an app.

The American Heart Association now classifies cardiorespiratory fitness as a clinical vital sign — the same category as blood pressure and heart rate. And yet almost nobody in medicine is measuring it. That gap between what the science says matters and what actually gets measured is exactly the kind of thing we fix at Stark.

The Decline Is Real — and It's Trainable

VO2 max peaks at around age 30 and then declines approximately 10% per decade. A sedentary person loses it twice as fast as someone who trains consistently. By the time most people hit their 50s and 60s, they've lost enough cardiovascular capacity that everyday tasks — carrying groceries, climbing stairs, keeping up with grandchildren — start to feel harder than they should.

Here's the part that matters: this is not fixed. The data shows that people in their 60s can increase their VO2 max by 19 to 22% with structured training. It is trainable at any age. The body responds to the right stimulus. But here's what makes all the difference — you have to know your baseline to know whether what you're doing is actually working.

Zone 2 cardio — the steady-state, conversational-pace training that everyone talks about — is genuinely effective for building cardiovascular base. But "I did 45 minutes on the bike" tells you nothing about whether your VO2 max moved. The only way to know is to measure. And to measure again. And to track the delta over time.

What Stark Is Doing About It

Starting in early October 2026, Stark is integrating VO2 max testing into our full assessment protocol. Every student, at some stage over the next six months, will know their number. Every training plan will include a VO2 max target. Every result will be tracked over time so we can see what's actually moving the needle — and what isn't.

This has been something I've been pushing toward for years. The science has been clear. The technology has been available. What was missing was making it a standard part of the process rather than an add-on. We're fixing that.

If you're already in the Stark system, stay tuned — your VO2 max test is coming. If you're not, my strong advice is to find a way to get this test done. It is one of the most important health metrics most high performers have never seen.

Health Is a Skill — and Now You Know Which One to Measure Next

The whole premise of what we do here is that health is not a mystery. It's a set of measurable inputs and measurable outputs. Every metric that matters can be quantified. Every lever that moves your health in the right direction can be identified and pulled deliberately.

VO2 max is one of those levers. It tells you how much cardiovascular capacity you actually have. It tells you whether your training is working. And it tells you — with striking precision — something about how long you're likely to live and how well you'll function while you're doing it.

That's a number worth knowing.