I Tracked 4 Fitness Metrics for 10 Months. Here's the Verdict

Which of the 4 fitness metrics on your smartwatch actually matters? An ER doctor ranks VO2 max, resting heart rate, heart rate variability, and heart rate recovery. I'm Dr Eoghan Colgan — 25 years in the NHS, mostly in emergency medicine. Medical school taught me nothing about longevity, so I do my own investigating. ▶ WATCH NEXT: Your Resting Heart Rate is a Longevity Predictor —    • Your Resting Heart Rate is a Longevity Pre...   📋 FREE GUIDE: The approach I use for health and longevity (sleep, nutrition, movement — no hype) — https://stressfreelongevity.com/free-... CHAPTERS 00:00 — Your watch tracks 4 fitness metrics 00:40 — What each metric actually measures 02:37 — VO2 max: your engine's top speed 04:06 — Resting heart rate: your engine's idle speed 05:48 — Heart rate recovery: how fast your brakes work 07:19 — HRV: heart rate variability explained 08:50 — How to improve every metric at once 10:12 — How much exercise actually matters 11:27 — Medications, conditions, and age 12:31 — Do you need to track all four? 13:06 — The final ranking 14:38 — What I track 16:18 — What you should do 17:37 — Final thoughts KEY TAKEAWAYS VO2 max has the strongest longevity evidence — a 5× mortality difference between the least and most fit Resting heart rate is the most practical to track daily — highest accuracy, zero effort, fastest feedback HRV gets the most attention but has the weakest longevity evidence in healthy adults Heart rate recovery has strong clinical evidence but is hardest to capture reliably on a smartwatch The same action — regular aerobic exercise — improves all four ABOUT THIS CHANNEL Stress-Free Longevity — evidence-based health and longevity content from a practising ER doctor. No biohacks, no supplement stacks, no hype. Just the science, what actually works, and how to make it sustainable. Subscribe for weekly videos on how to live longer and healthier without the noise 👉    / @stressfreelongevity   SOURCES Mandsager et al. JAMA 2018 — Cardiorespiratory Fitness and Long-term Mortality Kokkinos et al. JACC 2022 — Cardiorespiratory Fitness and Mortality Risk Zhang et al. CMAJ 2016 — Resting heart rate and all-cause mortality (meta-analysis) Cole et al. NEJM 1999 — Heart-rate recovery as a predictor of mortality ⚠️ Educational content only — not a substitute for medical advice. If you're unwell, see your doctor. #RestingHeartRate #VO2Max #AppleWatch