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When the heart is not beating in a regular pattern, this is referred to as an arrhythmia. When a human sleeps, a heartbeat with rates around 40–50 bpm is common and is considered normal. Bradycardia is a low heart rate, defined as below 60 bpm at rest. Tachycardia is a high heart rate, defined as above 100 bpm at rest. The American Heart Association states the normal resting adult human heart rate is 60–100 bpm. It is usually equal or close to the pulse measured at any peripheral point.
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The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide, but is also modulated by numerous factors, including, but not limited to, genetics, physical fitness, stress or psychological status, diet, drugs, hormonal status, environment, and disease/illness as well as the interaction between and among these factors. Heart rate (or pulse rate) is the frequency of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). Speed of the heartbeat, measured in beats per minute
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