Heart Rate Variability (HRV)

Heart Rate Variability is the variation in time between your heartbeats, measured in milliseconds (ms). Higher HRV points to a more flexible, responsive autonomic nervous system. Lower HRV can follow hard training, poor sleep, alcohol, illness, or stress.

Why HRV is personal

There is no universal "good" HRV. Values vary by age, sex, fitness, genetics, and circadian rhythm. What matters is how your current HRV compares with your own baseline.

Rune 1 builds a personal baseline over time and flags daily values as above, near, or below that baseline. A single low reading matters less than a multi-day trend.

When Pulsyn measures HRV

Rune 1 captures HRV during sleep and at quiet moments when you are still. Overnight HRV is particularly useful because the body is relaxed and the measurement is less affected by movement or mental load.

How HRV feeds other scores

HRV contributes to several Pulsyn scores:

• Readiness Score: a key contributor comparing your HRV to baseline.
• Sleep Score: deep-sleep HRV adds autonomic context to the night.
• Body Battery: low HRV can increase the drain rate.
• Biometric Age: HRV is one of the model inputs.

Interpreting your HRV

• A rising trend over days often signals good recovery.
• A sustained drop can mean you need more rest or recovery time.
• Compare today to your 7- and 14-day baselines, not to other people.

Sensor basics

Rune 1 uses optical sensors to detect blood-volume changes and compute HRV. For details on the sensor hardware, see the FAQ.