Cardio Fitness (VO2max)

Cardio Fitness is Pulsyn’s estimate of your VO2max (the maximum amount of oxygen your body can use during intense exercise), reported in millilitres per kilogram per minute (mL/kg/min).

Estimation tiers

The app uses two tiers:

• Resting-only: always active. Uses your resting heart rate, age, and sex in an age-adjusted heart-rate-ratio formula.
• Activity-refined: activates when you log at least 60 active minutes in the trailing 7 days. Adds heart-rate and cadence information from movement to refine the estimate.

ACSM percentile bands

Your VO2max estimate is placed into an age- and sex-adjusted percentile band using simplified ACSM tables:

• poor
• fair
• average
• good
• excellent
• superior

The band tells you how your estimate compares with population norms for someone of the same age and sex.

Trend direction

The app tracks a 30-day moving average against a 90-day moving average to determine whether your cardio fitness is:

• Rising
• Stable
• Declining

A difference of more than 1 mL/kg/min between those averages flips the trend arrow.

Confidence and accuracy

Cardio Fitness becomes more reliable as the model learns your personal response to rest and exertion. Early estimates may shift as the baseline matures.

Using the metric

• Use the percentile band and trend direction to track long-term progress.
• Do not compare raw VO2max values across different wearables; each device uses a different estimator.
• Pair Cardio Fitness with Strain Score to balance training load and fitness development.