7min

Heart Rate Variability

Heart rate variability refers to millisecond variations between heart beats. HRV is a non-invasive measurement of the autonomic nervous system (the body's main control center) and is widely considered the most comprehensive biomarker of health and fitness.

By measuring your autonomic nervous system, HRV reveals how your body responds to exercise, illness, treatment, recovery, inflammation, stress, mental health, and every lifestyle choice you make.

Heart rate variability is an umbrella term that describes general variability between heart beats; there are a number of specific HRV metrics used to analyze different features and patterns in heart rate variability that are correlated with different physiological states. Here is a description of our HRV score.

Basic

Example Output JSON
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Output

Data Type

Description

hrvScore

int

The HRV Score is based on RMSSD and scaled to a meaningful 1-100 score. This is an absolute indicator of Autonomic Nervous System health and strength.

Time Domain

Time-domain analysis shows how a signal changes over time and uses statistical methods to quantify the total amount of heart rate variability.

Example Output JSON
|

Output

Units

Data Type

Description

rmssd

ms

float

The square root of the mean of the squares of differences between adjacent inter-beat intervals. RMSSD is strongly backed by research and is considered the most relevant and accurate measure of the Autonomic Nervous System's Parasympathetic branch for short duration measurements.

sdnn

ms

float

The standard deviation of all inter-beat intervals throughout an entire measurement.

pnn50

%

int

The proportion of pairs of successive inter-beat intervals that differ by more than 50 ms.

meanRR

ms

float

The mean inter-beat interval is the average of the artifact corrected inter-beat intervals throughout an entire measurement.

Frequency Domain

Our Fast Fourier Transform (FFT) based frequency-domain HRV is the analysis of heart rate variability at certain frequency ranges associated with specific physiological processes.

Example Output JSON
|

Output

Units

Data Type

Description

hfPower

ms²

float

The high frequency (HF) activity in the 0.15 - 0.40 Hz frequency band. This band reflects parasympathetic (vagal) tone and fluctuations caused by spontaneous respiration known as respiratory sinus arrhythmia.

lfPower

ms²

int

The low frequency (LF) activity in the 0.04 - 0.15 Hz frequency band. This band can reflect both sympathetic and parasympathetic tone. A value is only available in measurement durations greater than 2 minutes. Measurements less than 2 minutes will receive a 'null'.

lfhfRatio

ms^2

float

The ratio of low frequency power to high frequency power. The ratio can indicate balance between sympathetic and parasympathetic tone. A value is only available in measurement durations greater than 2 minutes. Measurements less than 2 minutes will receive a 'null'.

hfPeak

Hz

float

The location in the high frequency spectrum band where the signal peaks.

lfPeak

Hz

float

The location in the low frequency spectrum band where the signal peaks. A value is only available in measurement durations greater than 2 minutes. Measurements less than 2 minutes will receive a 'null'.



Updated 04 Apr 2022
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