Resting heart rate (RHR)

Resting heart rate is the number of times the heart beats per minute while a person is awake, still, and relaxed, traditionally measured first thing in the morning before getting out of bed. Typical adult resting heart rate falls within a wide normal range, and well-trained endurance athletes often sit at the lower end of, or below, that range, since a more efficient heart pumps more blood per beat and therefore needs fewer beats per minute.

Consumer wearables estimate resting heart rate continuously using an optical sensor on the wrist, usually reporting the lowest sustained reading found during sleep, which differs from the classic single morning measurement but tracks similarly over time. This differs from heart rate variability, which measures the variation between beats rather than the beat rate itself; two people can share the same resting heart rate with very different variability, and the two metrics answer different questions about recovery.

A rising resting heart rate over several days, relative to a person's own baseline, is a widely used early signal of accumulated fatigue, illness, dehydration, or overtraining, and is tracked alongside training load, VO2 max, and sleep staging in quantified self routines. As with other wearable-derived vitals, a single elevated reading is common and often meaningless; the trend relative to personal baseline matters more, and a persistent, unexplained change is information to discuss with a clinician rather than self-diagnose.