The Rise of Athleticspan

A new approach to longevity that’s about keeping your body in the game.

Your body’s operating system changes without your consent.

It still resembles the body you remember. Same basic layout. Arms, legs, the usual equipment. But things click now. Things tighten. Stretching is no longer optional.

The old version of you — the one who could sleep four hours, drink three cocktails, play pickup basketball, and wake up mostly fine — has left the building.

In its place is a person who googles “hip mobility.” A person who tracks sleep. A person who has opinions about electrolytes. 

This is how I found myself at Eternal’s New York clinic, running on a treadmill in a mask that made me look like Bane from “The Dark Knight Rises,” while a trainer pricked my finger every few minutes to test lactate.

Welcome to preventive health in 2026.

The goal is not just to live longer. It’s to extend your athleticspan: the years when your body still lets you do the things that make life feel like yours.

Beginnings

I’d met Eternal founder Alex Mather at a Stanford health event in January. Before starting Eternal, he worked at Strava and co-founded The Athletic. 

I should disclose this up front: Mather offered me a free Eternal membership. I accepted as quickly as a New Yorker being handed courtside Knicks tickets.

Eternal is built around a simple idea: the way you take care of yourself should evolve as your body does. Not just because you want better lab numbers, but because you want to preserve the ability to keep doing the physical things you enjoy — running, lifting, hiking, skiing, tennis, basketball, keeping up with your kids or grandkids. 

Mather calls this athleticspan: the number of years you can keep doing the physical things that make you feel alive.

It’s a fitness-forward spin on concierge health. What if your doctor could also help you train for a marathon?

What if healthcare wasn’t just about treating disease — but also extending your ability to do the things you love?

The New Paradigm

Eternal is part of a broader shift: fitness and healthcare are merging. VO₂ max testing is showing up in luxury gyms. Outlive made healthspan mainstream. Andrew Huberman made sleep protocols dinner-party conversation. Hyrox turned functional fitness into a spectator sport. Somehow, longevity has moved from biohacker obsession to lifestyle aspiration.

Eternal’s program doesn’t talk much about supplements, peptides, or cold plunges. It focuses on the big things — diet, exercise, sleep — the everyday routines that add up to real change.

In that sense, healthy aging becomes a kind of long-term investment. Just as we save money during our working years to preserve freedom later, we can “bank” fitness, muscle, mobility, balance, and aerobic capacity while we’re strong. The goal isn’t to become superhuman. It’s to build enough physical reserve that the future version of you can still play, explore, compete, push, recover, and enjoy the body you live in.

The Basics

Eternal begins like most digital health platforms: You create a profile in the app. It asks about your medical history and performance goals. It helps you book a lab test. 

So far, pretty standard.

Then I booked a performance physical assessment. That’s where things got interesting.

I went into Eternal’s clinic in Manhattan. It looked less like a doctor’s office and more like a futuristic sports lab. A trainer named Kate walked me through a series of tests. 

First came the DEXA scan. I lay still as a robotic arm moved over me, limb by limb, compiling an internal audit of my body. Fat. Muscle. Bone. 

Then it was on to more tests. Grip strength. Hip strength. Power. Mobility.

For the balance test, I was asked to stand on one leg with my eyes closed. A task I’d thought was reserved for drunk people pulled over on the side of the road. You’d think it would be easier to do sober. Not for me. I lasted 22 seconds on my left foot, 13 on my right. 

Next up was lactate threshold testing. Lactate is an important marker of aerobic capacity for endurance athletes. Kate had me walk on the treadmill at a steadily advancing incline as every five minutes she pricked my index finger for a blood draw. By the third time she took my hand for a sample, I felt my whole arm tense up — some part of my brain rejecting the attempt to make me a human voodoo doll.

The lactate ramp took about 20 minutes. By this point I’d worked up a pretty good sweat. Kate offered me an energy bar. I scarfed it down in a few bites. One more test remained.

It was time for my VO2 max — the gold standard for cardiorespiratory fitness. 

Kate strapped the Bane-style oxygen mask over my face and had me run on the treadmill. Every two minutes she cranked up the speed. Soon I was going at an all-out sprint. I tried to summon whatever competitive spirit this 40-something-year-old had left. Just as I felt my legs about to give out beneath me, I hopped off, heaving to catch my breath.

The Results

After two hours, my performance physical assessment was complete. 

In the shower I reflected on the battery of tests I’d done. It felt like I’d survived an NFL combine for biohackers.

The whole thing is designed to answer the question: how well is your body built for the life you want to keep living?

Can you generate power? Can you recover? Are you balanced from left to right? Are you building enough aerobic base? Are you strong enough to protect you from injury? Are you eating enough to support the amount of training you do? Are your bones, muscles, heart, and metabolism moving in the same direction — or is one part of the system quietly lagging behind?

A few days later, an Eternal coach named Brooke walked me through my results. 

Lesson 1: My engine is strong.

My VO₂ max of 58.5 puts me in the 96th percentile. My peak power is around the 97th percentile. My upper-body strength tested near the top end. 

Lesson 2: My base needs work.

My aerobic base, as measured by a lactate test called LT1, is underdeveloped. This means even though my top-end engine is strong, my lower-intensity foundation needs work. Brooke recommended more Zone 2 cardio — the kind of cardio where you can still hold a conversation, but would prefer not to. Longer, 30–40 minute aerobic work of easy-to-moderate intensity. 

My stability could be better, based on the results of my single-leg, eyes-closed balance test. The test measures proprioception — your brain’s ability to know where your body is in space. Close your eyes, and your body can no longer cheat by looking. It has to know where it is from the inside.

How to improve this? Brooke suggeseted unilateral lower-body work. Single-leg, slow-tempo Romanian deadlifts. She suggested lifting barefoot or in socks to improve the brain-foot connection. 

Lesson 3: My recovery budget is underfunded.

Brooke used a sports car metaphor: Even if the car has a strong engine, without the right maintenance schedule, it breaks down. In my case, the maintenance issues could be addressed simply. Better nutrition. More iron. Improved sleep. The boring things that actually matter. 

For me, the headline was this: I don’t need to become more extreme. Setting a new bench press PR might be nice for my ego, but it’s not going to help my long-term goals. Instead, I should try to extend my athleticspan — to become more durable — to bank more aerobic base, muscle, balance, bone strength, and recovery capacity while I still can. 

No total life overhaul required. Just better inputs. 

The Takeaway

It’s easy to roll your eyes at all this. 

The VO2 mask.

The finger-prick blood tests. The deep dive into my brain-foot connection. There is a lot here that sounds like wellness theater.

But underneath it all is a serious idea: most healthcare waits until something breaks. Eternal is trying to catch things earlier — strength gaps, balance issues, asymmetry. A weak aerobic base. Early signs that performance today may be borrowing from resilience tomorrow.

It’s a different way to think about longevity. Instead of anti-aging and biohacking protocols, programs like Eternal ask a simple question: How do I stay capable? How do I preserve energy, strength, mobility, and independence to keep living the way I want?

Eternal’s answer is that healthy aging should be proactive, personalized, and connected to how you actually live. Your doctor should understand your labs, yes. But ideally, someone should also understand your training, sleep, nutrition, injury risk, goals, wearables, and recovery — and whether your current routine is supporting the lifestyle you want to maintain as you get older.

That is a very different model from traditional healthcare. It’s also different from pure fitness coaching. It sits somewhere in between: medical enough to be serious, performance-oriented enough to be motivating, and practical enough to be useful.

Eternal membership isn’t cheap. It runs $150 to $600 a month — which means this is not yet how most people will experience preventive care. It may remain a premium service for high-income fitness obsessives. The kind of people who own multiple wearables and think nothing of stepping inside a hyperbaric oxygen chamber.

But as a signal, it matters. Because Eternal is asking the right question. Not just: “Are you sick?” But: “Are you building enough physical reserve to keep living the way you want?”

Adaptation

After my feedback session with Brooke, I went for a long run through Hudson River Park. As I passed tennis and basketball courts, I thought back to the finger-prick lactate test. I gave myself a virtual pat on the back. I was doing something good for my body. Banking aerobic capacity. 

Then another runner blew past me on the right, leaving me in the dust as if I’d been running in slow motion. The competitive athlete in me would have taken that as a challenge. But I resisted the urge to try to catch up. 

I thought about something my old surf teacher once told me: “The best surfer isn’t the one who’s the best at surfing. It’s the one who’s having the most fun.”

Maybe that’s the real promise of athleticspan: Not outrunning time, but staying on the path long enough to enjoy the run.

Daniel Zahler is a healthcare strategist and communications leader working at the intersection of health, technology, and human behavior. He leads communications at Noom, the behavior change and whole-person health platform, where he shapes brand positioning, launches AI-powered health products, and translates clinical science into stories that move audiences and support business growth. He also writes Vitamin Z, a health media publication exploring how science, technology, and behavior change can help people live longer, healthier, more meaningful lives. Daniel is a former McKinsey consultant, exited founder, Harvard graduate, and Yale Medical School research fellow.