Do Your Lungs Limit Performance?

Many new runners complain that they can’t breathe even on short runs. Indeed, getting in enough air is foremost on their minds. It’s a marvel of physiology that enough air gets into our bodies, with our nostrils being no larger than the size of a pea. Even the space between semi-pursed lips is small considering the physiological demand for oxygen at high intensities. A large man who, at rest, breathes about half a liter of air per breath and about six liters of air per minute, breathes nearly 200 liters per minute while running hard. That’s 53 gallons of air entering the lungs each minute! Try filling a hose with 53 gallons of water in one minute. Gives you a lot more respect for the lungs.


Many runners get frustrated with their lungs because they perceive them to limit their ability to run. They claim they “can’t breathe” while running and are forced to stop so they can “catch their breath.”  Even trained runners sometimes feel this way. At first glance, distance running seems to have everything to do with big, strong lungs. After all, it is through our lungs that we get oxygen. But if the size of our lungs mattered, you’d expect the best runners to have large lungs. However, the best runners in the world are quite small, with characteristically small lungs. Your lungs’ capacity for holding air is mainly influenced by body size, with bigger people having larger lung capacities. Research has shown that the lungs do not limit your ability to perform endurance exercise, especially if you’re not elite. That limitation rests on the shoulders of your cardiovascular and metabolic systems, with blood flow to and oxygen use by the muscles the major culprits. There is no relationship between lung capacity and how fast you run a 10K. 

Our main stimulus to breathe (at sea-level) is an increase in blood’s carbon dioxide content. You breathe more during faster-paced workouts and races not because you need more oxygen, but because more carbon dioxide is being produced in your muscles and needs to be expelled through the lungs. Oxygen is all around us and has no problem diffusing from the air into our lungs. Once inside the lungs, oxygen diffuses into our blood. This elegant process is more than adequate—at sea level, your blood is nearly 100 percent saturated with oxygen, both at rest and even while running a race. (Some elite runners, whose hearts pump large quantities of blood through the lungs each minute, desaturate when running at race pace, a condition called “exercise-induced hypoxemia.”) The situation is slightly different at altitude, where you breathe more to compensate for your blood being less saturated with oxygen.

Coaches often tell their athletes to breathe deeply to take in more oxygen. But since your blood is already saturated with oxygen, it’s fruitless to take deeper breaths. Furthermore, since your diaphragm and other breathing muscles also must use oxygen while you run, the extra muscle contractions needed to take deeper breaths may steal some of the oxygen needed by your leg muscles. 

If getting more oxygen into your lungs doesn’t limit your ability to run faster, what does? Getting more oxygen to your muscles. And you do that by increasing the performance of your cardiovascular and metabolic systems, not by taking deeper breaths. There are a number of things you can do to improve cardiovascular and metabolic performance, including running intervals, running longer, and increasing your weekly mileage. 

Training your cardiovascular and metabolic characteristics improves your ability to transport and use oxygen, making you feel less out of breath. So next time you’re running up a hill and you’re thinking, “I can’t catch my breath,” don’t blame your lungs.

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