<Tr> <Td> </Td> <Td> This article needs more medical references for verification or relies too heavily on primary sources . Please review the contents of the article and add the appropriate references if you can . Unsourced or poorly sourced material may be challenged and removed . (July 2015) </Td> <Td> </Td> </Tr> <P> Heart rate is the speed of the heartbeat measured by the number of contractions of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide . It is usually equal or close to the pulse measured at any peripheral point . Activities that can provoke change include physical exercise, sleep, anxiety, stress, illness, and ingestion of drugs . </P> <P> Many texts cite the normal resting adult human heart rate as ranging from 60--100 bpm . Tachycardia is a fast heart rate, defined as above 100 bpm at rest . Bradycardia is a slow heart rate, defined as below 60 bpm at rest . Several studies, as well as expert consensus indicates that the normal resting adult heart rate is probably closer to a range between 50 and 90 bpm . During sleep a slow heartbeat with rates around 40--50 bpm is common and is considered normal . When the heart is not beating in a regular pattern, this is referred to as an arrhythmia . Abnormalities of heart rate sometimes indicate disease . </P> <Table> <Tr> <Td> </Td> <Td> Normal heart sounds Normal heart sounds as heard with a stethoscope </Td> </Tr> <Tr> <Td_colspan="2"> Problems playing this file? See media help . </Td> </Tr> </Table>

What is the average heart rate of a healthy person