Back-to-Back Long Runs
Piggybacking long runs has proven effective for ultrarunners racing 50K and beyond. It mimics ultra race-day fatigue but allows for a night’s recovery between sessions. Do a steady long run one day followed by a fast finish long run the next. This is especially challenging because you will be running hard the second day on fatigued legs.
Do back-to-back long runs once a week. Estimate your time for finishing the ultra and build up to running those total hours over two days. You want to run the full distance (combining back-to-back days) at least three or four times before the race.
For example, if you think you will finish in six hours, run three hours on Saturday and three hours on Sunday. Or four hours on Saturday and two hours on Sunday. Or five hours and one hour. Mix it up.
Sunday will be painful at first, but after you get warmed up it will feel easier. A great free program to follow is the Santa Clarita Ultra Training program.
It is important to slowly progress into these workouts, especially for those inexperienced with high mileage, by starting with relatively short back-to-backs during the pre-season months and building on those as race day approaches.