As the actor tells Variety’s The Big Ticket podcast, he would lock the door of the bathroom and knock out as many pushups as he possibly could, smartly putting paper towels down on the floor before beginning. He would then do arm curls in the mirror, I assume by just tensing up and using his own bodyweight, unless he brought his own dumbbells or just lifted toilet paper rolls.
Article source: https://www.cinemablend.com/news/2491645/x-men-alum-james-marsden-recalls-his-bathroom-ritual-before-every-cyclops-audition