The Rise of Athleticspan - by Daniel Zahler - Vitamin Z

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The Rise of Athleticspan<br>A new approach to longevity that’s about keeping your body in the game.<br>Daniel Zahler<br>May 19, 2026

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I tore my ACL playing soccer on Roosevelt Island.<br>League game. Slide tackle. Pop. Then came the MRI, surgery consult, ACL reconstruction, and physical therapy.<br>A year later, I was fully recovered. But something had shifted. I started thinking about fitness less as performance, and more as durability: how do I keep my body working well for as long as possible?<br>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.<br>Eternal is one of a new crop of platforms blending fitness with healthcare. The focus isn’t just lifespan, or even healthspan, but athleticspan : the number of years you can keep doing the physical things that make you feel alive.

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 (acquired by the New York Times).<br>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.<br>It’s a fitness-forward spin on concierge health. What if healthcare wasn’t just about treating disease – but also extending your ability to do the things you love?

Eternal is part of a broader shift: fitness and healthcare are merging.<br>VO₂ max testing is showing up in luxury gyms. Outlive made healthspan mainstream. 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.<br>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.<br>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.<br>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.<br>Because even though I take care of my body – exercise, nutrition, sleep – there’s still a question humming in the background:<br>Am I doing enough?

Performance Physical Assessment

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.<br>So far, pretty standard.<br>Then I booked a performance physical assessment. That’s where things got interesting.<br>I went into Eternal’s clinic in West Chelsea, near the High Line. 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.<br>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.<br>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.<br>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 guinea pig.<br>The lactate ramp took about 20 minutes. By this point I’d worked up a pretty good sweat. One more test remained.<br>It was time for my VO2 max – the gold standard for cardiorespiratory fitness.<br>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.

After two hours, the assessment was complete.<br>In the shower I reflected on the...