Yes. The nature of a filtering mask will mean that you will need to exert more energy to breathe through it. I would say that initially I felt that I couldn't

Yes. The nature of a filtering mask will mean that you will need to exert more energy to breathe through it. I would say that initially I felt that I couldn't cycle as far with a mask. But as I did it more it became easier, effectively like exercise for your lungs. And would say that if you have trouble with a mask walking then strenuous activity with one is probably not a good idea unless you work up to it. In terms of the effect, I live in London which is so-so when it comes to pollution. But you really notice the difference, especially going behind the exhausts of diesel vehicles.