Cardiac Output, Stroke Volume & Heart Rate (AQA GCSE Physical Education (PE))

Cardiac Output, Stroke Volume & Heart Rate

• Cardiac output can be defined as follows:

The volume of blood that is pumped by the heart every minute

• Cardiac output depends on:

  • Stroke volume = the volume of blood pumped by the heart with each beat

    • The stroke volume of a fitter individual will be larger than that of a less fit person; this is because their heart muscle is stronger and their heart is larger, so more blood can be pumped with each beat

  • Heart rate = the number of beats per minute

    • The heart rate of a fitter individual will be lower than that of a less fit individual; this is because of their larger stroke volume, which allows them to achieve the same cardiac output with fewer beats

• The relationship between cardiac output, stroke volume and heart rate can be represented by the following equation:

cardiac output (Q) = stroke volume (SV) x heart rate (HR)

• The equation can be used to calculate cardiac output

Interpreting heart rate graphs

The effect of exercise on heart rate

• Heart rate can be monitored during periods of rest and periods of exercise to assess the effect of activity on heart rate

Exercise and heart rate graph

• The graph indicates the following:

  • Person A is fitter than person B, as indicated by a very low resting heart rate

    • A resting heart rate as low as this indicates that person A is probably an elite athlete

  • Heart rate starts to increase before exercise begins

    • This is known as an anticipatory rise and occurs due to adrenaline release before the start of exercise

  • Heart rate continues to increase after the start of exercise

    • The heart rate of a less fit person (B) increases further and faster than a fitter person (A)

  • Heart rate stabilises at an increased rate during exercise

    • The heart rate of a less fit person (B) stabilises at a higher rate than a fitter person (A) during exercise

  • Heart rate takes time to return to resting heart rate after exercise ends; this is the recovery period

    • The heart rate of a less fit person (B) takes longer to return to resting heart rate than a fitter person (A)

The effect of exercise intensity on heart rate

• Heart rate can be monitored at different levels of exercise intensity to assess the effect of exercise intensity on heart rate

Exercise intensity and heart rate graph

• The graph indicates the following:

  • The resting heart rate here is around 65 beats per minute

  • Heart rate increases with exercise intensity

    • Low intensity exercise (walking) = 115 beats per minute

    • Medium intensity exercise (jogging) = 150 beats per minute

    • High intensity exercise (sprinting) = 185 beats per minute