Don't feel like running around a map for hours on end? Is Gladio's incessant need for running bringing you down? Do you have a rubber band laying around home? If so, perfect! Strap that bad boy on your joysticks and let Noct run Gladio's heart out on his own time! Just find an outpost that has a decent amount of space and watch 'em go! I let them do that while I slept (started at rank 3) and came back to rank 9! One more small session and Gladiolus will be the cardiovascular monster he so desires to be. Happy hunting!
Oh and a thanks to Sparkz1977 for reminding me that you need to use a Plug and play kit! Unfortunately running isn't enough activity to keep the controller on.