Unconventional exercise

Hmm are yo sure? Mine defiantly runs more, surely resulting in trapping more particulate to which bacteria would be attached and potential filtering more bacteria.

Also is just inhaling bacteria enough to causes a lung infection? By this I mean we must all inhale lots of bacteria but we rarely get an infection. Does there have to be an underlying weakness in the lungs or injury? Smokers tend to have more chest infections but I thought that is due to the weakened cilia being less able to clean the lungs? That being the weakness on top of the inhalation of bacteria.

Genuine question, I'm no biology expert.

No, not sure at all. Reduced function of the nose is part of the reason people get more colds in the winter at least (I read lots, but remeber poorly).

Somewhat connected....
I have recently discovered that my one year old has astma. I asked the doctor if we should keep him indoors during colder days (say minus 5 - 15). The doctor did'nt see any reason to unless he was already ill. So the extreme cold is possibly less harmful to our lungs then we imagine.

I know it's a magazine article but this appears to be false.
http://www.runnersworld.com/article/0,7120,s6-238-267-269-7442-0,00.html

I did'nt like the quote myself. There are simply too many variables. But I am frequently told that this is true (by very unqualified people though). I do get the cough mentioned in the article, and have dismised it as a side effect of the cold dry air, and not a sign of illness (It only lasts less than an hour).