Longevity Fitness.

VO₂ max, Zone 2, strength, body composition, and building a baseline.

A practical guide to the fitness metrics that help you understand where you stand — VO₂ max, Zone 2 cardio, grip strength, lean muscle mass, and body composition. Not a training plan. A framework for knowing what to measure, what the numbers mean, and what “fitness for the next forty years” actually looks like.

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What’s inside

Six chapters. Sourced and edited.

01VO₂ max and why it matters for longevity.
02Zone 2 cardio explained simply.
03Strength, grip strength, and muscle mass.
04Body composition and DEXA.
05Wearable data and what it actually tells you.
06How to build your own fitness baseline.

An editorial note

“We wrote this for the reader with a dozen tabs open who still can’t tell which sources to trust. Start here.”

— Prologue

We sell longevity protocols. We also write about them.

Prologue’s editorial team wrote this guide. We try to be useful without overpromising. We cite our sources. When the science is strong, we say so. When it is still emerging, we say that too.

Longevity Fitness.

Six chapters. Sourced and edited.

We sell longevity protocols. We also write about them.

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