What ‘Vitality Span’ Gets Wrong About Aging

“Vitality span” is one of those terms that sounds meaningful but doesn’t actually mean anything specific. It has no standard definition, no validated way to measure it, and no real clinical use. It’s a marketing tool built to sell programs, supplements, and subscriptions by making you feel like you’re missing something a product can give you. The idea it’s pointing at is real — the difference between living longer and living well — but the packaging hides the actual mechanism behind it.

That mechanism is VO2 max.

VO2 max — the maximum rate your body can use oxygen during intense exercise — is the single most reliable predictor of death from any cause in middle-aged and older adults, beating every blood marker in head-to-head comparisons ^[1]. The Baltimore Longitudinal Study of Aging found that the decline starts earlier than most people think: VO2 max drops roughly 10% per decade after age 30 in people who don’t exercise, and the rate speeds up after 50 ^[2]. This decline isn’t something you can stop completely. It’s a natural part of aging — a lower maximum heart rate, a weaker pumping capacity from your heart, fewer of the cell structures that produce energy, fewer blood vessels feeding your muscles, and less oxygen extraction by the muscles that are working.

What you actually control is your starting point and how fast you decline.

Someone who reaches 40 with a VO2 max of 45 mL/kg/min — roughly average for a 40-year-old man — and loses 10% per decade will be around 36 at 60 and around 29 at 70. Someone who starts at 35 mL/kg/min — around the 20th percentile — will be at 28 at 60, a level where basic daily activities (walking up stairs, carrying groceries, walking at a normal pace) start to use up a large chunk of their maximum capacity ^[1]. Above roughly 30 mL/kg/min, everyday activities feel comfortable. Below that, the same activities become tiring, draining, and eventually hard to manage.

This is the thing “vitality span” is trying to describe but never actually defines: the point below which your aerobic capacity starts to limit your independence. It isn’t a vague concept. It’s a specific number you can measure, track, and improve.

VO2 max comes from two parts working together. The central part is your heart’s ability to deliver oxygen-rich blood — determined by how much blood it pumps per beat and how fast it beats. The peripheral part is your muscles’ ability to actually use that oxygen — determined by how many energy-producing cell structures and blood vessels your muscles have, and how efficiently they use oxygen. Zone 2 training (steady, moderate-effort cardio) improves both, but mostly the peripheral side: it increases those cell structures and blood vessels in your muscles, improving how well your muscles use oxygen rather than how much your heart can pump . That’s why Zone 2 is the foundation and high-intensity interval training is the finishing touch — HIIT improves the heart’s side of things, but it needs the muscle-level foundation that Zone 2 builds first.

For a 45-year-old who never built a strong aerobic base in their 20s and 30s, the window to improve isn’t closed, but the approach changes. Zone 2 training at roughly 65-75% of max heart rate (the “conversational pace” where you can speak in full sentences but couldn’t comfortably sing) for 150-200 minutes a week has been shown to improve VO2 max by 10-15% in previously inactive middle-aged adults over 12-16 weeks . The gains are smaller than what a 25-year-old would get from the same routine, but they’re real and meaningful. A 10% improvement in VO2 max at 45 translates to roughly 5-7 extra years before you cross into the range where daily activities become a real limitation.

What does this actually look like? Three to four sessions a week, each 40-50 minutes at that conversational pace. A stationary bike, rowing machine, incline treadmill, or a flat outdoor walk. Heart rate around 130-150 bpm for most people (the exact range depends on age and resting heart rate). It should feel “comfortably hard” — something you could sustain for hours if you had to, but wouldn’t choose to. This isn’t a race. It’s building your base, and consistency matters far more than intensity here.

The question “am I healthy for 40” is the wrong question. The real question is “what did I build in my 20s and 30s” — because that shapes where you’ll be in your 60s and 70s. But if you didn’t build that base, the good news is you can still start building it now. The window is narrower, but it isn’t closed.

Bettering Me’s take: vitality span is a marketing term. VO2 max is a physical fact. Track the number. Build it while you still can.

A note on testing. The gold standard is a maximal cardiopulmonary exercise test (CPET) with gas exchange measurement — a gradually increasing workout on a treadmill or bike until you can’t continue, with a mask measuring your breath. This costs $200-400 and gives you your true VO2 max plus your specific heart rate zones. The practical alternative is an estimated VO2 max from a 1-mile walk test, a 12-minute run test, or an estimate from a device like a Garmin or Apple Watch. These estimates are off by 10-15%, but they’re good enough to track your trend over time. If you can afford one real CPET as a baseline and then use estimated tests every year after, that’s the ideal setup.

Disclaimer: This post is for inspiration and education, not medical advice. Everyone’s body is different, so please check with your doctor before changing your diet, exercise, or lifestyle routine. By using these tips, you agree to do so at your own risk.

References

^[1] Myers J, et al. "Exercise capacity and mortality among men referred for exercise testing." *NEJM*. 2002;346(11):793-801.. DOI: https://doi.org/10.1056/NEJMoa011858

^[2] Fleg JL, et al. "Accelerated longitudinal decline of aerobic capacity in healthy older adults." *Circulation*. 2005;112(5):674-682.. DOI: https://doi.org/10.1161/CIRCULATIONAHA.105.545459

Kurt Greiner

Kurt is a digital strategist and IT professional blending emerging technology with practical application to help businesses and individuals streamline their digital presence. His current work focuses on the intersection of intentional living and technological resilience, exploring how individuals can leverage modern tools to navigate the second half of life with purpose.