Resting heart rate and heart rate variability (HRV) are metrics that give consistent feedback on our health status and fitness.
The heart beat forms one of the most important indicators of health. The simplest measure is the pulse rate, or the number of beats per minute. It is controlled by the autonomic nervous system (ANS), that part of our body that works automatically, making sure we breath, and our blood keeps pumping.
When our body experiences stress, the heart beats faster in response. As the stress alleviates, the pulse rate returns to normal. But even at a steady pulse rate, let’s say 60 beats per minute (BPM) the time between each beat varies. Measured in milliseconds (ms), instead of being the expected 1000ms between each beat, the inter beat interval (IBI) varies: