What Is Heart Rate Variability?

Will Ahmed says heart rate variability is the amount of time between successive beats of the heart. More time variation between beats means the overall system is operating in a healthier way. It is a view into the autonomic nervous system, and the healthier pattern is sympathetic activity coupled with parasympathetic activity.

Sympathetic activation raises heart rate, blood pressure, and respiration. A thought like a lion in the room, exercise, or stress does it. Parasympathetic activity does the opposite and helps a person fall asleep. A long exhale is parasympathetic. Coupled together, the body keeps regulating its environment and heart rate variability measures higher.

He measured heart rate variability around the clock after medical research as a student at Harvard. The measure jumped off the page because interesting research already existed, but it could not be measured 24-7, and that limit is part of where WHOOP was born. WHOOP uses it for stress monitoring and the recovery score, baselines every member, and compares each day with that baseline. Trends over years show whether someone is getting healthier or less healthy. It is an important longevity indicator. Typically, heart rate variability drops with age: people in their 20s average anywhere between 80 and 100, the 30s fall toward 70, the 40s toward 50, and the 50s and 60s land in the 30s and below.