Heart rate

Heart rate is the number of heartbeats per unit of time, usually expressed in beats per minute. It changes with activity, health, age, and other conditions.

Cardiac conduction system: The network of specialized heart cells that generates and conducts electrical impulses coordinating heartbeats. Its electrical impulses determine how often the heart contracts.
Resting heart rate: The number of heartbeats per minute measured while a person is resting. A resting measurement gives a baseline distinct from exercise readings.
Bradycardia: A heart rate slower than the normal range for a person’s age and circumstances. It names an abnormally slow rate rather than heart rate in general.
Beat per minute: A unit expressing how many heartbeats occur in one minute. It is the standard unit used to report heart rate.
Sinoatrial node: A cluster of specialized cells in the right atrium that normally initiates each heartbeat. Its firing rate sets the heart’s usual rhythm and pace.
Maximum heart rate: The highest heart rate reached during maximal physical effort. Exercise prescriptions often use it to define intensity zones.
Tachycardia: A heart rate faster than the normal range for a person’s age and circumstances. It names an abnormally fast rate, which may have many causes.
Cardiac cycle: The sequence of events in one complete heartbeat, including contraction and relaxation. Each counted heartbeat corresponds to one cardiac cycle.
Electrocardiography: The recording of the heart’s electrical activity using electrodes placed on the body. An electrocardiogram measures beat timing directly from electrical signals.
Heart rate variability: The variation in time intervals between successive heartbeats. Beat-to-beat timing adds information that an average rate cannot show.

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