I have recently been diagnosed with paroxysmal atrial fibrillation, I take 120mg verapamil per day. How safe is it for me to continue weight training?

PAF. There is mounting data showing that athletes who generate a lot of upper body strain (ie rowers, weight lifters) have an increased incidence of a fib, felt to be due to back pressure on the heart during straining that ultimately stretches out the top chambers which is where atrial fibrillation comes from. As you continue weight lifting, be aware that your paroxysmal afib may become persistent.