I have cultured for MAC in the past, but do not currently. I was a frequent lake and indoor pool swimmer from age 5 through my 20's. My alternate days were dedicated to running outdoors (even in winter). I became a daily indoor pool swimmer around age 30 and continued this until recently (the past 4 months). For reasons totally unrelated to this discussion, I changed doctors 4 months ago and based on a previous MAC culture (about 9 months), the new doctor suggested I reduce indoor pool swimming as a precaution. His thoughts were that over time, the body becomes overloaded by exposure to a variety of germs and eventually we test positive for these. He is being cautious, but I am 60 years old and don't want to take a chance. My previous doctor, however, thought swimming was fine, even when I did culture positive for MAC. I don't think anyone knows if there is a direct connection. The benefits of swimming for so many years far outweighed the risks for me. My new doctor, a CF specialist but not part of the certified CF center that had treated me in the past, has recommended Yoga and I find this a fantastic addition to my other daily exercise routine. It has helped me lengthen my inhalation period and control my breathing. It is great for flexibility, strength and balance, which is helping me in my power walks and weight training.
I would say this. Follow your instincts. I have always lived by the motto "I can live with my mistakes but not with my someone else's." When my instincts tell me that something is not good for me, I don't do it. If I make a wrong call, I can handle that. But when I go against my instincts and the results are not good, I become angry at myself for not listening to my instincts.