Runner’s Heart

I love the heart.

When I speak at conferences, I often make the joke that, as a distance runner, I have a great capacity to love because I have a large heart. That one-liner always produces a few laughs from the audience (but has seldom helped me to get a date). One of the most elegant adaptations your body makes to endurance training is an increase in the size of your heart’s left ventricle as a way to increase your stroke volume and pump more blood. The larger your left ventricle is, the more blood it can hold; the more blood it can hold, the more blood it can pump to the muscles you use to run.

Imagine what your heart goes through during training. After you complete a difficult workout, your heart says, “Geez, Jason is running hard workouts on a regular basis that cause me to reach my maximum capability to pump blood. If he keeps doing this and I don’t do something, I’m not going to be able to survive.” Thus, in response to the imposed threat of running at your heart’s maximum ability to pump blood, your heart responds by increasing its pumping strength and by enlarging its most important chamber—the left ventricle—so that it can send more blood and oxygen to the working skeletal muscles. Pretty elegant, huh? An enlarged heart is so characteristic of individuals who do a lot of endurance training that scientists and doctors have given it the medical term, athlete’s heart. A larger heart increases the maximum volume of oxygen you consume per minute (VO2max) because it gives you a larger max stroke volume and cardiac output.


The cardiovascular aspect of training is one of the biggest topics I talk about at conferences when I speak about running because it gets to the heart (pun intended) of the matter. If you want to be a better runner, it starts with your heart. The hearts of the best endurance athletes in the world pump twice as much blood each minute when working at their maximum capacity compared to the heart of the average person.

If you want to find out more about your heart and you’re unable to attend the conferences where I speak, now you can download the exclusive PowerPoint slide presentations from all my lectures at

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