Kick Fever Fitness – How Improving Your Cardiorespiratory Fitness Can Strengthen Your Immune System

Your breath can cue a cascade of benefits to your immune system, and the better your cardiorespiratory fitness, the more protected you may be.

Take a deep breath. That simple act can help bolster your immunity. Start huffing and puffing during a workout, and that will improve it too. The lungs and heart power the many pathways of immunity, which is why the way you breathe and your overall cardiorespiratory fitness are key.

Your lungs move oxygen-rich blood to the heart via capillaries, and then your heart extracts oxygen from the blood and pumps it around your body, like to the muscles you’re contracting as you walk or cycle or squat, says Benjamin Levine, M.D., an exercise science professor at the University of Texas Southwestern Medical Center in Dallas. That boost in muscle movement and oxygen flow also sparks the increased circulation of immune cells. Exercise trains your heart and lungs to pump oxygen-rich blood more efficiently and, by extension, send more immune cells into active duty.

But focusing on your breath even as you’re sitting still helps. When you inhale and exhale fully and slowly, you turn on our parasympathetic system — the calming lever of our nervous system, says Susan Blum, M.D., the author of The Immune System Recovery Plan. (The message is sent via the vagus nerve, which runs from the brain stem through the lungs and heart and into the diaphragm and intestines.) Flipping the switch likewise deactivates the sympathetic nervous system, our fight-or-flight response that pumps out stress hormones, like cortisol and adrenaline, says Thomas W. Decato, M.D., a pulmonologist in Spokane, Washington.

One powerful immunity benefit of diffusing stress hormones? Cortisol and adrenaline find their way into our lymphoid tissue (located in the thymus gland and elsewhere), where budding immune cells are maturing. “Those hormones can damage cell development, so the more you can spare developing immune cells from exposure, the better they’ll function when mature,” says Dr. Blum.

“Just 10 minutes a day of any belly breathing that expands the base of the lungs can make a difference,” she says. Try this pranayama technique used in yoga: Inhale deeply and slowly through your nose, then gently and fully exhale through your nose; continue “pulling” and “pushing” the breath at a controlled pace.

It’s the power of exercise, via the heart-lung action, that then spurs the circulation of immune cells. When you’re at rest, your immune cells are usually hunkered down in the lymphoid tissue, like soldiers awaiting the call to deploy. “But when we breathe deeper and more quickly and our heart rate goes up and muscles contract during exercise, it signals those powerful immune cells to circulate and patrol the body for pathogens for up to three hours afterward,” says David Nieman, a professor at Appalachian State University in North Carolina. Over time, this uptick in roaming immune cells translates into fewer sick days compared with non-exercisers. Moderate to vigorous exercise most days does the trick. (FTR, proper sleep can help boost your immune system too.)