Type Property


A quantity sample type that measures the standard deviation of heartbeat intervals.


static let heartRateVariabilitySDNN: HKQuantityTypeIdentifier


These samples use time units (described in HKUnit) and measure discrete values (described in HKStatisticsQuery).

Heart rate variability (HRV) is calculated by measuring the variation between individual heartbeats. While there are multiple ways of computing HRV, HealthKit uses SDNN heart rate variability, which is calculated using the standard deviation of the inter-beat (RR) intervals between normal heartbeats (typically measured in milliseconds).

See Also