HRV is not a measure of change in your resting heart rate over time, its a measure of the difference on a per beat basis. Even if your BPM is 60, your heart doe

HRV is not a measure of change in your resting heart rate over time, its a measure of the difference on a per beat basis. Even if your BPM is 60, your heart doesn't beat exactly once a second, it will actually vary in length by some number of milliseconds back and forth. This is what is measured when talking about HRV. It is believed to occur as the parasympathetic and sympathetic nervous system "fight" over raising and lowering the heartrate. The symbiosis between them lands on a steady rate per minute with fluctuations on a per beat basis. https://en.wikipedia.org/wiki/Heart_rate_variability https://en.wikipedia.org/wiki/Heart_rate_variability