Any changes to heart rate, stroke volume and cardiac output are determined by the intensity and duration of exercise.
Changes to heart rate during exercise
Heart rate is measured in beats per minute (bpm). During exercise the heart rate increases so that sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen. An increase in heart rate also allows for waste products to be removed.
Maximal heart rate can be worked out by the following equation:
Maximum HR = 220 - age
Question
What is the maximum heart rate of a 16-year-old person?
204 bpm
Change to stroke volume during exercise
Stroke volume increases which means more blood is pumped out of the heart each time it contracts.
Changes to cardiac output during exercise
At rest a person's cardiac output is approximately 5 litres per minute, while during exercise it can increase to as much as 30 litres per minute as both their heart rate and stroke volume increase.
Question
Work out the cardiac output of a person at rest with a heart rate of 70 bpm and a stroke volume of 70 ml.
Compare that to their cardiac output when they are taking part in exercise as their heart rate increases to 120 bpm.
Cardiac output = SV 脳 HR
Q at rest = SV 脳 HR
Q at rest = 0.07 脳 70
Q at rest = 4.9 l
Q during exercise = SV 脳 HR
Q during exercise = 0.07 脳 120
Q during exercise = 8.4 l
During exercise there is a greater cardiac output because the athlete requires more blood and oxygen to be transported to the working muscles. The increase in the amount of blood also helps with the removal of waste products lactic acid and carbon dioxide.
Changes to blood pressure during exercise
As exercise increases, cardiac output (Q) also increases. This has the effect of increasing blood pressure.
A typical blood pressure reading for a person at the start of exercise would be around 160/85 mmHg.