What You Need to Know About the Air You Breathe

The moment you were born, two balloons inflated inside your chest, began pumping and haven't stopped since. Those sacs of air—a.k.a. your lungs—are responsible for transferring oxygen to your bloodstream and removing waste in the form of carbon dioxide.

Most of the time you're hardly aware of them, but if you're grinding up a long climb, you might notice how hard you're breathing and wonder whether those balloons are any bigger than a couple of grapes. In fact, your lungs are plenty large. "Most of us are born with enough lung capacity to escape a lion," says Norman Edelman, MD, senior medical advisor for the American Lung Association. But if your lungs are compromised, says Edelman, they can slow you down. And many cyclists may unwittingly be doing theirs harm.

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Here's what's going on. When you ride at your aerobic peak, you breathe in massive quantities of air—an estimated 150 liters per minute, says David M. Systrom, MD, assistant professor at Harvard Medical School and director of the advanced cardiopulmonary exercise-testing program at Brigham and Women's Hospital in Boston. And with every breath, you suck in microscopic bits of soot, exhaust, dust, aerosols and other pollutants, all of which can cause inflammation.

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Ride near heavy traffic or an industrial area, and the problem is exacerbated. Ozone, the main ingredient in smog, is a lung irritant that can give you "what amounts to a sunburn in your lungs," says Edelman. Runners who exercise in areas with high ozone levels develop thickened lungs, similar to what happens to smokers, according to the Health Effects Institute, a Boston nonprofit organization that studies the effects of pollution on health.

And scientists who looked at cyclists exposed to ozone while riding reported that their lung function decreased by 22 percent and their endurance by 30 percent. What's more, researchers in Canada discovered that people who are chronically exposed to such pollutants are 20 percent more likely to die from lung cancer than those who breathe clean air—the same odds you'd face if you lived with someone who lights up.

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This doesn't mean you have to strap on a gas mask every time you head out or resign yourself to a life of Sufferfest videos in the basement. Your lungs have the capacity to filter occasional doses of bad air. But if you live in a city or near an industrial area, you can take steps to minimize your risk. Ride on lightly traveled roads or in parks, and head out either early in the morning (ozone is lowest from 6 to 10 a.m.) or during off-peak traffic hours. The website airnow.gov offers a daily air-quality report, or you can download the American Lung Association's State of the Air app for on-the-go readings.

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To a lesser extent, air temperature can also affect lung function. You might think a cough or wheeze is a sign you're out of shape, but it's not a normal fatigue response, says Tod Olin, MD, a pulmonologist with National Jewish Health in Denver. It may be exercise-induced bronchoconstriction (EIB), a form of asthma that kicks in during exertion or right afterward. Cold, dry air—as well as pollution and allergens--is known to trigger EIB in people who are susceptible.

Olin says about 15 to 25 percent of the population suffers from it. "Someone with untreated EIB doesn't have a normal airway; it's like trying to pass oxygen through a small-bore straw," says Randy Wilber, PhD, FACSM, senior sports physiologist for the US Olympic Committee. And, he adds, restricted airflow can impact performance. A sore throat, clogged nose or tight chest may also be signs your body is reacting to bad air.

The bottom line is that air should feed your lungs the same way that a healthy diet fuels your muscles. Here's how to keep your lungs healthy and working hard.

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Anatomy of a Breath

1. The nose warms and humidifies the air before it reaches the lungs and filters out pollutants. You're more likely to irritate your lungs when you breathe through your mouth.

2. The tubes that carry air into the lungs (the bronchi) have taste receptors. They don't actually "taste" anything, but the bronchi will dilate when they sense something bitter.

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3. Though lungs don't stretch or bulk up the way your quads might, there is evidence that they do adapt to activity. Some high-altitude athletes have larger-than-normal lungs.

4. The diaphragm does most of the work of pulling air into your lungs. Breath training makes it thicker and stronger.

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5. Because the left lung shares space with the heart, the right one is slightly bigger (with three lobes, not two) but no more powerful. The surface area of your lungs is about the size of a tennis court.

6. Pollution can thicken the lining or scar it, both of which cause lung elasticity and function to diminish.

7. Microscopic sacs (alveoli) transfer oxygen into the blood and remove carbon dioxide. The average adult has about 300 million of them.

Fact: Lungs follow a circadian rhythm. One study showed they are most open between 4 and 5 p.m.

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Embrace Hard Efforts

Riding your bike makes your heart and muscles handle oxygen more efficiently. But studies show that doing high-intensity interval training has a more positive effect on respiratory muscle strength than doing long, steady efforts, says Systrom. (Here are some interval workouts you can add to any of your regular rides.) And a recent Health Canada study suggests that when the air quality is poor, going hard may be the best approach. In the experiment, cyclists who did a low-intensity ride in polluted air had to breathe harder (to take in more oxygen) to keep the pace. But when they rode at high intensity, they needed the same amount of oxygen regardless of the pollution level.

The finding surprised the study's lead researcher, Michael Koehle, MD, PhD, associate professor in the School of Kinesiology and the Division of Sports Medicine at the University of British Columbia. Koehle speculates that the body's adrenalin-fueled fight-or-flight response—which opens small airways in the lungs—overrides the effects of pollution.

Muscle Up

Not all breaths are created equal. To the extent you can, inhale slowly and deeply during your ride. This removes carbon dioxide more efficiently than rapid, shallow breathing, says Systrom. You can also try doing resistance work for your breathing muscles.

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When you work hard, they can be greedy, consuming about 10 to 15 percent of the oxygen you take in, says Alison McConnell, PhD, professor of applied physiology at Brunel University in the United Kingdom and author of Breathe Strong, Perform Better. Plus, studies on cyclists have found that when these muscles fatigue, they steal oxygen from the arms and legs. Conversely, well-conditioned breathing muscles improve performance and use less oxygen. McConnell suggests a method called inspiratory muscle training, during which you add resistance when you breathe in.

It works most effectively if you use a product designed to make it harder to inhale. McConnell recommends one called POWER-Breathe, but there are others available. Do 30 reps twice a day, aiming for consecutive slow, deep breaths.

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Keep 'Em Comfy

Lungs prefer warm, moist air. A study of elite cross-country skiers found that areas of their lung tissue became scarred from repeated exposure to cold, dry air, says Wilber. In frigid weather, ride during the warmest part of the day and use a neck gaiter around your nose and mouth to humidify the air. If you have asthma-like symptoms, such as a cough, wheezing, or shortness of breath, especially after exercise, check with your doctor.

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