My Bio AgeMy Bio Age

Methods & Sources

My Bio Age turns Apple Health metrics into two headline numbers: Fitness Age and Biological Age. We lean on peer-reviewed research, transparent inputs & limitations (no coefficients disclosed), and conservative assumptions so you can see what’s changing and why.

Fitness Age

Fitness Age is powered by VO₂max, which Apple Watch measures during eligible outdoor workouts. Apple Watch provides VO₂max estimates for those workouts; we compare your VO₂max to the FRIEND normative database based on age and biological sex. The resulting percentile is mapped to the age where that percentile is average.

  • VO₂max samples are filtered for recency and workout quality.
  • We smooth spikes with an exponentially smoothed moving average to resist short-term noise.
  • Weekly digests (delivered via local notification) highlight improvements or declines compared to the prior week.

Biological Age

Biological Age blends multiple recovery and cardiovascular metrics into a single z-score that is then translated into an age scale. The core inputs include HRV (SDNN), resting heart rate, walking heart rate, heart-rate recovery, sleep duration and quality, and activity. When VO₂max is available, it supports the broader context alongside those recovery signals.

Each metric is standardised against your personal long-term average and population norms. Inputs adapt based on availability: if VO₂max or another signal is missing, remaining inputs expand cautiously to maintain stability without exaggeration. Exact coefficients remain proprietary and stay on-device; we document inputs, references, and limitations so you know what influences the score.

Caveats

Apple Watch VO₂max is an estimate derived from outdoor exercises that meet Apple’s criteria. Accuracy depends on workout conditions, motion, and consistent wear. We flag missing or low-confidence samples so you know when to repeat a measurement. Biological Age is a wellness indicator, not a medical diagnosis.

References