4 Ways Your Heart Adapts to Aerobic Exercise

image of Cathe Friedrich in a Fit Split cardio workout

Aerobic exercise – we know it’s good for your heart and our heart is an important muscle! Through aerobic exercise, you can improve your cardiovascular health and develop more stamina and endurance. The benefits of cardio can positively impact every aspect of your life. When you’re aerobically conditioned, you no longer feel as tired or breathe as rapidly when you do something strenuous.

If you play any sports, you also need the cardiovascular adaptations that aerobic exercise brings about. A number of sports require participants to have good endurance. Not to mention, aerobic exercise can prolong your life. In fact, results of a study published by the National Cancer Institute shows that physical activity can extend lifespan by as much as 4.5 years. Plus, it can improve health span, the number of years you enjoy good health and functionality.

Why is aerobic exercise so effective for enhancing the quality of life? This type of exercise increases the body’s energy demands. To meet these requirements, more oxygen must be delivered to muscles and tissues and your heart has to work harder to get it there. To make oxygen delivery easier, your heart adapts to exercise in several ways. Let’s look at some of them, so you can better understand how aerobic exercise improves the health of your heart and gives you more stamina and endurance.

The Structure of Your Heart Changes

Like other muscles in your body, including skeletal muscles when you resistance train, your heart slightly enlarges in response to exercise. A study conducted by researchers at Harvard showed that after only 90 days of exercise, the heart muscle thickens and becomes larger. The biggest changes are to the left and right ventricles of the heart. The right ventricle sends blood to the lungs while the left ventricle delivers blood to the body. Both ventricles expanded in size over a 90-day period in response to aerobic training.

These adaptations make sense, don’t they? If you need to deliver more blood and oxygen to tissues, larger ventricles can push blood out with more force. Other studies show that the wall of the left ventricle thickens over time in response to aerobic exercise. A thicker ventricle can generate more force for the delivery of blood and oxygen as well. If you stop exercising for a long period of time, these changes typically reverse and the ventricles return to normal size since you no longer need the extra blood flow.

Stroke Volume Goes Up

Stroke volume is the amount of blood the heart can eject with each heartbeat. If it can eject more oxygenated blood with each contraction, it becomes more efficient at delivering oxygen to tissues. Better oxygen delivery gives you an advantage when you exercise. One reason stroke volume goes up is that the left ventricle (the chamber that pumps blood to the body) enlarges, as mentioned above. The other reason is that regular exercise increases the volume of fluid in your blood vessels. When more volume enters the ventricle, the wall of the ventricle stretches and can contract with more force. This, too, increases stroke volume and enhances oxygen delivery.

The increase in the size of the heart enables the left ventricle to stretch more and thus fill with more blood.  The increase in muscle wall thickness also increases the contractility resulting in a higher stroke volume at rest and during exercise, increasing blood supply to the body.

Resting Heart Rate Goes Down

People who are aerobically fit tend to have a slower resting heart rate and that’s because the heart becomes a more efficient pump in response to regular aerobic exercise training. We know that exercise increases the heart’s stroke volume, the volume of blood delivered with each beat. That means better oxygen delivery during exercise and at rest. So, your heart doesn’t have to beat as many times per minute at rest to meet the body’s oxygen requirements. The greater the stroke volume, the slower your heart can beat and still deliver enough oxygen.

Blood Pressure Often Goes Down

Aerobic exercise has another heart-healthy benefit – it reduces resistance within the walls of blood vessels. When your heart pumps blood through your arteries to the various parts of your body, those blood vessels provide varying degrees of resistance. If the resistance is high, your heart has to pump against more force as the vessel wall is too tight and that raises blood pressure. Aerobic exercise helps to relax the inner walls of arteries. One way it does this is by boosting the production of nitric oxide, a gaseous chemical. Production of more nitric oxide helps expand the size of the blood vessel and reduce resistance.

In response, you may notice a drop in blood pressure after starting an aerobic training program. That’s one of the benefits of aerobic exercise – it improves how blood vessels function and lowers blood pressure. However, blood pressure often rises during exercise itself, especially during heavy resistance training. That’s why it’s a good idea to see your doctor before beginning a strength training program if you have poorly controlled high blood pressure.

The Bottom Line

So, now you know how your heart and blood vessels change, over time, in response to aerobic exercise. The take-home message from numerous studies is that regular, aerobic exercise is linked with a lower risk of developing coronary heart disease, even in individuals who don’t start exercising until middle age. Even when cardiovascular disease develops in fit individuals, it tends to occur later in life. So, all of these changes add up to lower cardiovascular risk, the odds of having a stroke, and other health benefits as well. Yes, aerobic exercise changes your heart structurally and functionally, but those chances are beneficial for health. Why not take advantage of all aerobic exercise has to offer and work up a sweat?



Harvard Gazette. “Exercise changes structure of heart”

National Cancer Institute. “NIH study finds leisure-time physical activity extends life expectancy as much as 4.5 years”

Science Daily. “How Exercise Changes Structure And Function Of Heart”

Circulation. 2003;107:e2-e5.


Related Articles:

Is Resistance Training a Good Cardiovascular Workout?

These Two Types of Exercise Are Synergistic for Heart Health

What is Athletic Heart Syndrome?


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