@c130herkengineer I was diagnosed last year as an incidental finding to a precautionary CT scan done to check for calcification. Like you, I've been active and have been competitive in marathons (did Boston a few times) and have been part of a competitive men's masters rowing team. I'm at 4.8 cm. My initial "cheap" CT scan came back at 5.0 but I had a subsequent gated CT scan with contrast six months later that showed 4.8 (so there may be some variation when you have a CT scan with contrast) and I just had my one-year follow-up scan that showed no change. My doctor, who trained at the Cleveland Clinic, and who seems pretty current with the literature, advised me to keep most of my workouts in a zone 2 range and to keep my peak heart rate below 80% heart rate reserve and not to lift more than 50% of my body weight (the advice on lifting limits seems to be particularly variable among doctors). I might suggest you check out the Aortic Athletes group on Facebook which has links to some of the videos by some the experts in the field of exercise for people with aneurysms (e.g., Dr. Timothy Churchill at Harvard, Dr. Alan Braverman at Wash. U, and Dr. Prakash at U. Texas) as well as a community of people facing the same issue. It's a shock and it will take a few months for you to adjust, but you'll get there.