Question: What happens to my heart when I exercise?

Steve Faulkner answered on 15 Mar 2012:

When you exercise your heart rate will increase, meaning that your heart will be faster. This allows the body to supply blood to the working muscles more quickly. As oxygen is carried in the blood this means that more oxygen can be transported to these muscles and allow them to keep contracting, assuming that you are doing an “endurance” activity. During exercise, your heart rate will continue to rise even if your exercising at the same level/intensity (steady state) due to what is known as cardiac drift. If there is a sudden increase in oxygen demand due to a hill or surge in pace for example, then your heart rate will rise accordingly to meet the demand for oxygen/blood by the working muscles. Once you stop exercising, your heart rate will reduce, but can remain slightly elevated for a while afterwards depending on the duration and intensity of your exercise.