Diaphragmatic breathing is not just for opera singers and die-hard yogis—professional bodybuilders and athletes are turning to breath practices to boost endurance for peak performance.

Cardio is thought to be the main source of building aerobic durability, and while it’s definitely an important factor, it’s not the only one. “I hear it all the time—athletes don’t understand why their energy can be so erratic when they’re in the best shape of their lives,” breathing coach Dr. Belisa Vranich says, explaining that more often than not, the link between breathing and fatigue is overlooked.

A good cardio workout strengthens the heart so it can better supply blood and oxygen to the muscles. But if the breathing muscles are not strong the body experiences what Vranich calls “perceived fatigue.” She explains that, “The heart muscle is ready to keep powering through reps, but muscles that help empty and fill the lungs aren’t doing as well,” something that breathing exercises help prevent.

According to Dr. Vranich, a complete workout is one that targets the body and the lungs. “When athletes learn to engage their full diaphragmatic breathing power, they access more oxygen,” Vranich says, which aids in building endurance as well as helping to lower blood pressure, reduce stress hormones, improve sleep, and boost overall energy levels.

If you’re a competitor, you want to train your hardest without having to stop to catch your breath.OPUMP Breath training device helps strengthen the diaphragm, lungs, and abdomen to beat assumed fatigue and encourage lower body breathing, or horizontal breathing. It also help improve flexibility in the thoracic cavity for maximum oxygen intake. “Unlocking the diaphragm’s full range of motion drastically increases the level of oxygen per breath,” Dr. Vranich says, which lets the body relax fully and disengage the fight-or-flight response that is otherwise triggered from vertical breathing or holding your breath.

Vranich suggests practicing “lion’s breath” or “fire breathing,” a series of fast and forceful exhales that warms the body and works the inner abs. Other techniques include lying on your back while doing exaggerated belly inhaling and exhaling with a weighted-plate on the abdomen, and stretching in the cat-cow tradition.

“We were born breathing horizontally until we were told to suck in our gut to look good, or we stopped breathing completely due to stress. Learning to breathe right is the easiest thing you can do to improve your general health and nourish the body,” says Dr. Vranich.