Rather than race-specific training, ultra-marathoners don’t have the natural ability needed to be elite on the track or in the marathon. That’s why LR posters like to speculate on how fast the top East-Africans could run ultras.
And East Africans have no skills to finish a 100 miler.
Ran a marathon awhile back as part of a running group. Some of the marathoners who did well that I ran with also did ultras. They passed me about 23 miles into the race and seemed so effortless, whereas the rest of the runners in our pack were struggling at that point. Do the ultrarunners have as much of an advantage, being an overdistance sport, on the roads as you'd think? Or is it like a completely separate sport?
An ultrarunner I know, who was won some 100 milers, dropped into our local road marathon and ran 2:47. He didn't slow down in the last 10K, his splits were super even throughout the race. It was very impressive. The marathon "specialists" I know all fade a bit at the end. Running more than marathon distance gives them some unique insight into how it should feel at the later stages, that most marathoners only figure out after a bunch of marathons.
Ran a marathon awhile back as part of a running group. Some of the marathoners who did well that I ran with also did ultras. They passed me about 23 miles into the race and seemed so effortless, whereas the rest of the runners in our pack were struggling at that point. Do the ultrarunners have as much of an advantage, being an overdistance sport, on the roads as you'd think? Or is it like a completely separate sport?
An ultrarunner I know, who was won some 100 milers, dropped into our local road marathon and ran 2:47. He didn't slow down in the last 10K, his splits were super even throughout the race. It was very impressive. The marathon "specialists" I know all fade a bit at the end. Running more than marathon distance gives them some unique insight into how it should feel at the later stages, that most marathoners only figure out after a bunch of marathons.
Good Marathon runners can pace themselves at least as good as an ultrarunner. Of course as a good Marathon runner you run a lot closer at your limit as any ultrarunner would. It's a lot easier to pace yourself perfectly right 5 - 10 minutes under your PR, than close to it.
every time I go a further distance than I ever have before, my muscles thereafter have no problem doing a lesser distance. for example the first time i ran a 70km race, I couldn't walk for the days afterwards (DOMS), but my muscles repaired stronger, so after that I never had a problem in a 42km race (assuming I slept and ate properly in the day/s prior). Same thing happened when I did my first 100km.
So their muscles will be ready for a 42km whereas yours might not in the closing stages of the race if you have only done 30 or 35k in training. but they still have to get everything else right including pacing, fuelling etc.
Personal experience - I've run a lot of marathons and have shifted more to ultras the last few years. When I go back and race a marathon now, what I've found is I'm not as sharp (not as much focused speedwork) so my top-end speed isn't great, but I can hold a moderate pace far better for longer. I ran Boston last fall in a time I didn't think I was prepared to do since I was coming off some summer ultras and hadn't done much in the way of speedwork or tempo. I held my $hit together long enough and ran a good time - had I run ~10 seconds/mile slower, I feel like I could have run another 5-7 miles at that pace, but if you asked me to run 26.2 at 5 seconds/mile faster, it would have been a disaster!
Part of that is being older I guess (50+) and losing some speed. But I do feel ultras have made me stronger for longer, and I am a little better about hydration/fueling and proper pacing so I tend to not fall apart at the end of a marathon.
One of the guys I coach high school XC with is a shorter distance guy, and he would shake his head when I would say "I'm good on endurance, but I need to focus on shorter speedwork to get ready for this marathon!" Not many people take that approach!
As a mid-pack ultrarunner, I can testify that I performed better in ultras this year training like I was prepping for a road marathon with flat threshold and other speed work and then only a couple weeks of very training.
Last year, I focused on climbing, climbing, climbing and more climbing, and I was slower. Same mountainous courses.
This doesn't exactly answer the question, but it possibly adds a relevant data point.