So many factors with no universal answer. The size at which it can burst is different for everyone. What was the size 4 or 5 years ago before it got to 50mm? Have you been lifting weights all along and it would not be new activity? What type of exercises have you been doing?
My ascending aorta was at ~ 54mm at surgery. I was doing a similar exercise routine up until surgery. But it wasn't new to me. Same routine for many years. Actually I varied between medium weight & medium reps to higher reps. And lots of elliptical and abdominals. Also cycling and walking. And some of the cycling trips were long, like up to 165 miles. One such trip last year, rode from Homestead, Fl. to Key West, Fl. and back. That was very flat though except for the few bridges and high winds resistance.
Slow & steady. Listen to your body. But, I'm told you will get no warning if and when it ruptures. By that time it is usually too late.