There was a time in my life that I would start a new workout routine and instantly my lungs would respond. I remember being so amazed when I started swimming again after a long break and my lung function jumped to some of the highest levels I had seen in a long time. I naïvely assumed that this meant that if people started exercising they would absolutely see positive changes in their lung function. See, the problem with CF is sweeping generalizations just don't hold up. What works for you doesn't mean it will work for someone else and even more mystifying is what works for you now may not work for you later.
About two and a half years ago. I had just gone through a horrible time in my health and very slowly started working out again because it was the first time in a long time my body would even allow me to work out. I started with water aerobics and had trouble keeping upon with the 60+ year old women in my class. Seriously, I was half their age and most of them smoked me in the pool with workouts. Humbling to say the least.
I eventually worked up to swimming laps. I did about 15 laps and took minute long breaks between each laps to catch my breath enough to try another lap. I was humiliated and ashamed that I was the youngest person in the pool and yet everyone's beautiful continuous laps that started long before I arrived at the pool and continues far beyond the time I left made me feel weak and broken. I would repeated excuses in my head as I did laps, "I have 30% lung function, but when I was healthier I could swim like you too," as if the other swimmers could read my mind and would be less judging when they heard my silent explanation.
I made progress and started swimming for about 15 minutes with fewer breaks although I only managed to do breaststroke (the easiest stroke for me) and hadn't built up the lung power to try front crawl. I was feeling less ashamed and humiliated until and older woman made a comment, "You are like my husband. You work out for about 15 minutes...I guess that is all you need." She was more talking out loud than saying it in judgment, but I remember feeling like I never wanted to show my face there again. I wasn't being lazy and working out as little as possible, it was all I could manage!
Eventually, swimming got easier. I started swimming 40 laps (front crawl!) and often only stopped because my oxygen sats dropped too low and forced me to stop. Over time, I slowly worked up to 50 laps, then 60 laps, and currently I do 75 laps before I call it quits. I don't stop between laps and no longer need to pull myself from the pool because of oxygen issues.
And as for my naïve assumption all those years ago? Over two years my lung function hasn't budged even 1% point. Not yet, at least. I think about how hard it was to do two consecutive laps two years ago and now I can do 75 in a row and it is hard to believe my lung function hasn't changed. However, I know my lungs have changed! They are in much better condition than they were two years ago. I know my oxygen saturation is better and overall my lungs are healthier and clearer. I may not have been rewarded with higher pfts, but I do believe exercise is allowing me to have a good quality of life despite my low lung function. Also, when I am in the pool I don't feel sick, I feel strong and healthy and powerful now. That is something, as someone with CF, I don't often feel out in my regular life. So emotionally and mentally it helps me too. I guess when I think about all the benefits exercise has given me, I can't be too disappointed that it hasn't helped my lung function (at least not yet...).