Probably best to do an apples-apples comparison and run another marathon race, then evaluate
In general, however, adding variety will help with motivation and subsequently improve fitness which will leave plateaus behind. Try new trails, new road routes, new workouts, new running partners, etc. Enter different kinds of running events...
In general, however, adding variety will help with motivation and subsequently improve fitness which will leave plateaus behind. Try new trails, new road routes, new workouts, new running partners, etc. Enter different kinds of running events...