Physiology

Resting heart rate is a simple daily readout of fitness and fatigue

A lower number usually means a stronger heart - a sudden rise is worth paying attention to

Resting heart rate - beats per minute while calm and at rest, ideally measured right after waking - is one of the simplest fitness markers available without any special equipment. As cardiovascular fitness improves, the heart becomes more efficient and pumps more blood per beat, so it needs fewer beats per minute to circulate the same amount of blood. Well-trained endurance athletes often sit in the 40s, while an average untrained adult is typically 60-100 bpm.

Beyond the long-term fitness trend, resting heart rate is also a useful short-term signal. A noticeable rise of 5-10+ beats per minute above your personal baseline on a given morning is a common early indicator of accumulated fatigue, incoming illness, dehydration, or poor sleep the night before - often showing up before you consciously feel run down. Tracking it for a few weeks establishes a personal baseline that makes these spikes easy to spot.

The most useful way to use it isn't chasing an absolute number, since individual variation is large and some of it is genetic, but watching your own trend over time and treating an unusual morning spike as a signal to consider an easier training day rather than pushing through as usual.

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