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 80 ml.
Compare that to their cardiac output when they are taking part in exercise and their heart rate increases to 200 bpm and stroke volume increases to 120 ml.
Q at rest = SV Ă— HR
Q at rest = 70 Ă— 80
Q at rest = 5600 ml
Q at rest = 5.6 l
Q during exercise = SV Ă— HR
Q during exercise = 120 Ă— 200
Q during exercise = 24 000 ml
Q during exercise = 24 l
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.