HRV measures the different intervals between your heartbeats over time. So while heart rate records your beats per minute (bpm), HRV tracks the variance in your bpm. In general, you want to see a higher HRV, which means that your body is more capable of adjusting to and recovering from stressors. It’s a sign that your nervous system is in good health and responsive to environmental demands. Low HRV, on the other hand, typically means that either the sympathetic or parasympathetic branch (usually the former) is dominating. This could indicate a lack of sleep, dehydration, or illness. HRV also tends to decline with age. – Maria Teresa