Training your lungs to the point of collapse may not sound appealing if you aren’t a free diver or a movie star playing a supervillain. Since most of us don’t have access to “Captain Kirk,” as Robbie calls him, playing in the water without supervision is extremely risky. However, the central idea still stands: by training our diaphragms to function more efficiently, we can increase the air we take in.

First, remember that “strong lungs” are not option. Lungs are airtight sacs that attach to the rib cage and fill with air. However, deliberate exercises can strengthen the diaphragm and intercostal muscles responsible for filling those bags, which in turn may significantly impact the body’s ability to use and distribute oxygen.

In 2012 an Olympic study found that synchronized swimmers, who can hold their breath for an average of one minute, have the second-highest aerobic capacity after long-distance runners. Breathing trainer device can increase lung capacity, which is why many top-tier runners opt to train like swimmers.

While the average person breathes in and out over 22,000 times daily with little thought, athletes in specific fields cannot afford to take their breaths and leave them randomly. This is why diaphragmatic breathing, which involves “stretching” the diaphragm, is a common technique among swimmers, runners, scuba divers, and yogis.

If you’re sitting at a desk and want to demonstrate diaphragmatic breathing, place one hand on your upper chest (where you usually suck in air) and one hand down on the tummy. Allow your abdomen to push out as you inhale through your nose to increase diaphragmatic expansion. Next, pull your stomach toward your spine as you let your breath out through your mouth. Warning: the more erect you are, the more challenging this exercise will be. Initially, you should try lying down.

This is typical for breathwork, though. You should expect difficulty. Most people need help fitting in essential self-care practices like yoga and meditation as is. At the peak of a bench press set, it’s not uncommon for lifters to forget to take a breath. So, it’s only sometimes top of mind to routinely employ breathing exercises, even though there are many to choose from (including nasal breathing, pursed lip breathing, four-square breathing, and Buteyko breathing).

However, this may be where the help of breathing trainers comes in handy. UFC legend Bas Rutten created the O2 Trainer, a rubber mouthpiece worn in the mouth like an adult pacifier to limit airflow, many years ago. Throughout his life, Rutten has had asthma, but as a child, he realized that he could run faster in the days following an asthma attack because his breathing muscles had worked so hard. The idea is essentially a “dumbbell for the diaphragm,” a form of resistance training.