On Sunday afternoon I was in town (Stockholm) and “amused” myself for a moment by checking how many pedestrians had their mouth open or closed. I did not count anyone that was talking to each other or in a cell phone, none who were laughing/smiled and also none that made faces/movements with their lips and mouth (surprisingly many). If I would have been given the chance to study these grimacing people a little longer, most likely they would have opened their mouth, since this often go hand in hand..
The result: A quiet Sunday afternoon, not a stressful Monday morning at 7 am, 80 people out of 100 had their mouth open and only 20 had their mouth closed. Needing to breathe through your mouth at a normal walk indicates a) poor breathing habits, b) habitual mouth breathing, c) poor physical fitness, d) oxygenation starvation in body cells and e) a higher level of inner stress.
It would be great if you want to check this out for yourself where you live to see if they are mouth or nasal breathers while walking, and share your result here.