With the low lung function I have (less than 30% FEV1) the most I ever really do is walk. SOMETIMES I manage a flight of stairs, but I usually I take elevators. Lately, I've been more motivated to actually go to a park and walk since the weather has been nice. I think as long as you get 30 minutes a day of getting your heart rate up a bit you'll feel better about yourself and your lungs will thank you. I get short of breath very easily and have not yet gotten into the portable O2 deal but figure it will happen sooner rather than later.