What Your Lung Capacity Can (and Can’t) Tell You About Your Fitness, According to a Pulmonologist

Of all the ways to measure you physical fitness, what can you learn from lung capacity? “Lung capacity is the total amount of air you can get into your lungs in one breath,” says Dr. Russell Buhr, assistant professor of medicine, division of pulmonary and critical care at the David Geffen School of Medicine at UCLA. This seems like a pretty important part of any workout. But what’s the link between lung capacity and fitness level? Is your lung capacity actually a good indicator of anything?

Dr. Buhr says lung capacity varies a lot from person to person, and there isn’t an absolute value that is considered “good” lung capacity. “It is most closely related to your sex, age, and height and the ratio of your limb length to your torso. Taller people have bigger lungs than shorter people, people with long torsos more than short torsos and long legs for the same height,” he explains. What they’re really checking is to see if it’s close to what’s expected for someone your body size. He adds that certain conditions, like pulmonary fibrosis or scoliosis, can reduce your lung capacity.

This all means that it’s tricky to get an estimate on your lung capacity without going to see a doctor, who will typically use a spirometry test to determine the amount of air you are breathing in and out. “There are home spirometers you could buy, but unless you are trained to use them, they won’t provide reliable numbers,” says Dr. Buhr. Since at-home lung capacity tests won’t be very useful, if you do have concerns about your breathing, Dr. Burh says to see your doctor for a lung function test.

“Lung capacity itself isn’t the most important measure of fitness, which really is a combination of factors like your cardiovascular fitness, endurance, and muscle efficiency,” Dr. Buhr says. “Exercising won’t significantly change your lung capacity, which is really determined by your anatomy. The major determinant of fitness is the efficiency of your muscles at using oxygen. When we exercise, the biggest thing that’s happening are changes to the way our body gets more efficient,” he explains. Your endurance increases as your heart and lungs become more efficient at getting oxygen to your muscles.

While lung capacity alone can’t tell you much about how fit you are, it can indicate when there is a problem going on. “What is meaningful is if you start to feel more short of breath doing the same exercise you have been doing, that could be a signal of a heart or lung condition,” Dr. Buhr says, though he does note that significant obesity can cause abdominal fat to compress the lungs which can also cause shortness of breathe.

“Regardless, staying fit and active is a great way to feel better and keep your breathing feeling strong,” he says.

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