I had always heard that same thing, but I don't necessarily think it's that cut and dry. At the end of 2009 my FEV1 was 49%. In September of 2010 it was 58-59%. Now it is 66%. Some of it is due to starting Cayston. But the main thing is that I've started exercising 4-6 days a week. My doc is convinced that is why my numbers keep rising.