Use your nose for breathing. All of the time and also when you exercise. Just your nose, not your mouth.
You possibly saw, heard or read the news recently about what goes on up your nose, and that a new class of antibiotics has created because of the discoveries made there. So what? you might be thinking, and what's it got to do with breathing and exercise? Well, those of you who have worked with me know that I am a proponent of nasal breathing over mouth breathing, and this has particular relevance when exercising.
Well, when air goes up it, the nose removes dust and particles as small as pollen grains with extreme efficiency. It humidifies this air if required to it to prevent dryness of the lining of the lungs and bronchial tubes. And it warms cold air to body temperature before it hits your lungs. That's three actions that are very important for lung health.
Unfortunately, breathing through your mouth results in dry or cold air going right down to the lungs, likely constricting the bronchial network. Particles containing viruses and bacteria go directly to your lungs.
Via the nose, bacteria and viruses have to "run the gauntlet", so to speak. They do battle with the current residents. As mentioned in above, they have discovered a new class of anti-biotic in our noses.
When is the most air required? That's when you're breathing hard. When you're engaged in exercise, perhaps? Thousands of litres of air in and out of the lungs...
What would be better for the lungs? Cold, dry and dirty, or warm, moist and filtered?
Lastly, and with significance for exercising is Nitric Oxide(NO). This gas is released in the nasal passages during nasal breathing. When NO enters the lungs, it opens up the bronchial network and can increase arterial oxygenation - more O2 in the blood. Further, in the bloodstream it is a vasodilator (it dilates the blood vessels). So, the more you breathe through your nose - imagine a tough session - the more NO can open your lungs, improve blood oxygenation, and then increase the vasodilation of your blood vessels. So, more oxygen can reach those hard working muscles.
(PS, Nitric Oxide is also an anti-microbial. It gives bacteria a real hard time.)
So, the crux of it: The more you use your nose to breathe, the healthier your lungs will be. The better they perform, the better you can perform.
So, at the gym, or out on a run, and all the time, use your nose.