Why Does Your Heart Rate Increase When You Exercise?
Much of this answer revolves around oxygen. The fact is that oxygen supply and demand is central to virtually all physically-demanding activities.
Oxygen enters the body via the lungs. From there, it is absorbed into the bloodstream and pushed out to the muscles via the heart.
When you exercise, your muscles require increased oxygen levels to exert additional energy and accommodate the growing intensity of the task. To provide the muscles with the oxygen that they demand, the body responds by upping its oxygen supply and taking in more. Thus, chemicals like norepinephrine are released by the sympathetic nervous system, which signal the body to accelerate its breathing rate (thus bringing in oxygen more quickly).
In turn, the heart responds by beating faster as a means to increase the blood flow (and oxygen supply) to the body’s various muscle groups.
At the same time, the sympathetic nerves also compress the body’s veins, thereby making them narrower. This increases the velocity of blood flow throughout the body, meaning that the heart must pump faster to continually recycle the returning blood.
The rate at which your heart will pump blood during exercise depends on a variety of factors, including:
Your heart’s health
Overall fitness level
Intensity of the exercise
Due to this supply and demand, as well as the physiological processes playing out, the heart must work harder and increase its beats per minute to get oxygenated blood where it needs to go and to remove carbon dioxide.
The reason why those who are physically fit tend to have a lower resting heart rate is that their hearts have become stronger. As a result, their cardiovascular systems use less effort to supply the body with the necessary amount of oxygen.
In addition to a lower resting heart rate, this kind of cardiovascular conditioning can also make a person faster.
The reason for this comes back to the question of oxygen supply and demand. As the cardiovascular system becomes more efficient and effective at intaking and utilizing oxygen, the faster a person becomes and the longer they can sustain the intensity of their activity. Of course, this also works in conjunction with muscle conditioning.
Understanding the Heart’s Role in Exercise
So, why does your heart rate increase when you exercise?
Because, in a nutshell, as you exercise, the body’s response is to increase oxygen demands, which the heart is responsible for pushing all throughout the body.
While this is very foundational knowledge on the heart’s role in exercise and the benefits provided to the heart by working out, it is important to know how the body works.