Heart Rate & Cardiac Volumes

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

Heart rate (HR)

  • This is the number of times your heart beats during a particular time. It is usually measured by the number of beats per minute (bpm).
  • During exercise heart rate increases to enable more blood (and therefore more oxygen) to be circulated around the body to muscles.
  • Anticipatory rise is the phenomenon where heart rate increases even before you begin to exercise. Your body knows what to expect and releases adrenaline which increase heart rate in preparation.

Cardiac volumes

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

Stroke Volume (SV)

  • This is the amount of blood pumped from the heart (left ventricle), each time the heart contracts.
  • At rest, this is between 70-100ml, during exercise the figure increases to 113-179ml.
  • The fitter an individual is, the higher their stroke volume. More blood circulating means more oxygen and more energy available for muscles.

Cardiac Output (CO)

  • This is the amount of blood ejected from the heart in the space of a minute.
  • It is calculated by multiplying the stroke volume and the heart rate (beats per minute).
  • Cardiac output (CO) = Stroke volume (SV) / Heart rate (HR)
  • This can range from 5,000ml/min at rest to 35,000ml/min during maximal exercise.

End Diastolic Volume (EDV)

  • The amount of blood within the left ventricle prior to the contraction (systolic) phase of a heartbeat.

End Systolic Volume (ESV)

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

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