Cardiac Output & Heart Rate

heart rate cardiac output

Here we explain heart rate, cardiac output, stroke volume, and how they change during physical exercise.


Heart rate definition

Heart rate is the number of times your heart beats during a set time. We usually measure heart rate as the number of beats in one minute or bpm.

Heart rate during exercise

During exercise heart rate increases to enable more blood to circulate around the body to the muscles. As a result, blood supplies more oxygen muscles to meet increased demand.

Anticipatory rise is the phenomenon where your heart rate increases even before you begin to exercise. Your body knows what to expect and releases adrenaline which increases heart rate in preparation.

Cardiac volumes

Cardiac volumes describe the amount of blood moved by the heart.

Stroke Volume (SV)

The amount of blood the heart (left ventricle) pumps, each time it contracts is the stroke volume. At rest, this is between 70-100ml, during exercise the figure increases to 113-179ml.

The fitter you are, the higher your stroke volume. More blood circulating means more oxygen and more energy available for muscles.

Cardiac Output Equation(CO)

The amount of blood ejected from the heart per minute is the Cardiac output. We calculate it by multiplying the stroke volume (in millilitres) and the heart rate (beats per minute). It ranges from 5,000ml/min at rest to 35,000ml/min during maximal exercise.

Cardiac output (CO) = Stroke volume (SV) / Heart rate (HR)

End Diastolic Volume (EDV)

The amount of blood in the left ventricle prior to the contraction (systolic) phase of a heartbeat is the end-diastolic volume.

End Systolic Volume (ESV)

End systolic volume is the volume of blood remaining in the ventricle after contraction. The stroke volume is equal to EDV-ESV.


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