HRV (heart rate variability) is the variation in the time interval from one heartbeat to the next. It can be used as an indicator of physiological stress.

Most people think of heart rate as the average number of beats per minute but your heart rates changes from beat to beat. HRV measures this naturally occurring irregularity in heart rate.

Ava measures the ratio between low frequency and high frequency waves in your heart rate. Because Ava measures HRV using this ratio, a lower number means you are less stressed.

A "normal" HRV ratio varies widely from person to person. Once you start to see a stable baseline of your HRV ratio, you can learn about your body's physiological stress level by looking for an increase or decrease in the HRV ratio.

The key takeaway about HRV is that a lower HRV ratio indicates lower levels of stress.