Your lungs are a unique organ. They reside deep inside your body, but are the only internal organ that has continual and wholesale exposure to the outside world. Think about it: Every time you breathe in—roughly 20,000 times per day for the average adult—you’re drawing in on average about 4 or 5 liters worth of your outside environment directly into your body.

All day long, your lungs work hard to extract the oxygen needed to run your body while discarding the pollution and other junk they don’t. And this process happens billions upon billions of times over the course of your lifespan.

Your lungs are quite plastic in nature, meaning they respond to changes in the environment. This is both a good and bad thing. Your lungs are naturally quite tough to deal with all the unhelpful particles in the air, but they’re also very vulnerable to damage and disease. And, as you age, your lung capacity naturally starts to shrink.

The good news is your lungs are quite responsive to the conditioning effects of regular physical exercise, and swimming might just be the best option for improving lung health. This superior form of cardiovascular exercise seems to have an outsized effect on the state of your lungs, and this is a good thing for overall health, fitness, and well-being.

There are five primary ways swimming can support better lung health and the long-range ability of your hard-working lungs to keep serving the trillions of oxygen-hungry cells that make up your body. 

Increased Lung Capacity and Breath Endurance

Swimming can actually make your lungs bigger and more efficient in how they process the air you breathe. That’s according to a 2015 study that compared the volume of air swimmers’ lungs could hold compared to sedentary control subjects and elite football players.

How much swimming increases lung volume isn’t entirely understood, but as with improvements from consistent physical activity in your heart function, it seems your lungs expand to help your cardiovascular system become more efficient over time.

When your heart rate climbs during a tough workout, that’s a response to your body’s need for more oxygen. That oxygen is supplied by your lungs, and causes you to breathe harder during exercise. Your lungs get better at meeting these demands as you train consistently, and that can result in some structural adaptations—such as an increased lung capacity—over time.

In short, as you train, your cardio-pulmonary (heart-lung) system gets more efficient in responding to the demands of increased physical activity, which is why when you’re in shape, you don’t get winded as easily as when you’re out of shape.

Boosted Breath-Holding Capability

Swimming is remarkably good at building lung capacity and breath endurance, not just through the effects of cardiovascular training but also through breath control. Marathon runners, cyclists, and virtually every other land-based athlete can gasp anytime they want and take in as much air as they want. Swimmers, however, have to time their breaths with their stroke and have a limited instant in which to capture the air needed.

That much-needed next breath isn’t always available at the exact instant you want to take it in. This means your body has to adapt and get used to waiting a little longer, which can build breath endurance.

Reduced Symptoms of Asthma

A common storyline during the Summer Olympics is the star swimmer who got into the sport as a child because a doctor recommended it as therapy for asthmatic lungs.

Asthma is a chronic condition that narrows airways. It causes wheezing and difficulty breathing and can be a big problem, potentially even deadly.

Swimming has often been recommended to children with asthma as a way of exercising that can build up breath capacity and endurance, which can in turn reduce the problematic symptoms of asthma.

Breathing in warm, humid air—the kind often found in indoor natatoriums—has long been thought to be helpful for keeping your lungs supple and your airways open. Breathing in cold, dry air can be especially triggering for many people with asthma, so during the winter especially, heading to the pool for a workout rather than running outside in the snow is probably a better option for people with asthma.

Increased Core Strength

Swimming just might give you abs of steel. But even more importantly, it strengthens your core as a whole, which is home to the respiratory muscles that move air into and out of your lungs.

Every time you breathe in or out, a bunch of muscles help push that air where it needs to go. You have to have a certain amount of strength to do that, and studies have shown that people who swim and practice breath control have stronger respiratory muscles.

This might be helpful, especially as you age, for slowing the rate of lung capacity decline and in helping offset the effects of certain ailments. For example, people with a disease called chronic obstructive pulmonary disease experience an increase in breathlessness as their lung capacity decreases. In COPD, air gets trapped in the upper part of the lungs, and that can make getting enough oxygen especially difficult. Swimming may be able to help offset some of those losses by strengthening the respiratory and other muscles in your torso and core that can support better breathing and fully emptying of your lungs on each breath. 

Supports Spine Health and Good Posture

In addition to helping build strong respiratory muscles, swimming can also build a super strong core that lets you stand or sit up straight. Standing or sitting up straight doesn’t just help you project an air of confidence. It actually helps you get more air into your lungs. That air is then processed by your lungs and used to propel your body through the day and all your many tasks.

“You may think that sitting with slumped shoulders or bending at your back instead of your knees sometimes won’t hurt you. But small changes in how you hold yourself and move can add up over a lifetime,” according to an article by the National Institutes of Health.

Sitting slouched or bent compresses your lungs and gives you less space to work with when drawing in a new breath, but improving your spine and core muscles’ ability to hold your body up means there’s a greater volume of air that can flow in and out of your body.

Poor posture can also contribute to the development of headaches and migraines, decrease flexibility and balance, and can reduce your ability to remain independent as you age. But swimming is an excellent way to support good posture because it can alleviate back pain and make your core stronger.