Millions of people wake up to a heart rate variability score on their Fitbit, Apple Watch, WHOOP or Garmin. Few know what the number means, and even fewer know how it should shift as they age.

What is heart rate variability (HRV)? As popular as the metaphor may be, a healthy heart doesn’t beat as regularly as a metronome. In fact, it changes its rhythm with each beat. Heart rate variability ...

Your heart rate naturally rises and falls throughout the day. Factors like caffeine intake, exercise, and stress levels can all affect your heart rate. But a heart rate that’s consistently too high or ...