At the top of the heart, a small bundle of cells known as the sinoatrial node regularly send out an electrical impulse. The signal causes the walls of the heart to contract, sending blood into the ventricles and then out to circulate through the body. For some of us the rhythm of the heart is quite irregular and that arrhythmia can be dangerous. But small variations in heart rhythm are actually very healthy.

Imagine someone who’s heart beats at 60 beats a minute, or once a second. That rate is actually not exactly one beat per second but may deviate by a few milliseconds quicker or slower each time. That variability is actually quite healthy and very important to our physical and emotional health. Those who have more “heart rate variability” are more resilient and adaptable to stress. In essence they are more fluid and flexible and stressors don’t bother them quite as much. Those who have less variability and a more regular rhythm have less resiliency and can become more easily aroused and stressed out.