Thanks Hoka for sponsoring this shoe contest. I think Kipchoge would crush any ultra race and world records if he had the financial incentive to give it a shot. A lot of people don't realize that many Ethiopians also train on trails at high altitude and many of these are tough trails. What is it, 23,000+ high school kids run a mile under 5 minutes every year. After high school, where I didn't break 5 minutes (5:02 PR), I went and did a 50 mile with no training and ran a bit over 9 hours. A friend of mine who also I don't believe broke 5 minutes in high school jogged to a bit over 8 hours. Yes, these are slow times, but I beat a significant number of those high school kids who are running under 4 minutes could crush it on the small ultra scene.
Ultra's are definitely a niche calling and the biggest problem with ultra races in the United States at least is that all of the really interesting and exciting races are basically impossible to get in, so they end up not being competitive, not to mention the general lack of interest due, among other things, to low cash prices and lack of tv and news coverage. People generally run ultras because they are an adventure that they often don't know if they are even going to finish.
In terms of impossibility of getting into races, I would say two of the most interesting races with cool histories are Badwater (135 miles from Death Valley to Mt. Whitney trailhead) and the Barkley marathon (~100 miles with 60,000 ft of ascent). Barkely accepts 40 people and Badwater only 100. Not to mention, Badwater used to an incredible race where you went all the way to the top of Mt. Whitney, but due to National Park Service regulations you can no longer climb the mountain, so in my mind at least the race became much less interesting. Even Western States limits the field to less than 400 people due to regulations in the parks, so I don't think you can really call that a competitive race - especially as they don't invite many talented runners to enter.
If you are looking at the United States, the JFK 50 mile race is probably the most prestigious, just because pretty much anyone can get in if you pay the steep entry fee (now over $200 bucks which is a lot for ultras), and they typically have a field of around 1,000 people. So, even though it is the oldest and one of the biggest in the US, local 10ks often have more runners.
So, I actually think that fastest known times are more prestigious and competitive in the United States, because anyone can do them at any time and there is no insane cost or field limit.
I definitely recommend that you check out this website: https://fastestknowntime.com/ They include comments on the best FKTs of the year.
I personally think that the Appalachian Trail FKT may be the most prestigious and competitive. If you have not seem seen the videos and read about Scott Jurek and Karl Meltzer's record-setting runs I recommend you check them out.
*What are the most prestigious/most competitive ultramarathons in the world to win?
As mentioned above, the United States is lame in terms of the ultra scene due to limits on field size for all the cool races. I think there is no doubt that Comrades is the most competitive and prestigious due to field size and the number of talented racers running, although UTMB should also be in the discussion as it is a different kind of race.
Japan's ultraunners are also insane, and Lake Saroma is one of the most high profile races. This past year when Nao Kazami set the world record, 5 people finished the first marathon in 2:33! That is incredible for a race that is almost 2.5 marathon. http://japanrunningnews.blogspot.com/2018/06/kazami-breaks-100-km-world-record-at.html
The International Association of Ultraunners also has 100km and 24 hour championships that could be reasonably considered world championships.
*What is your favorite ultra? What is the most beautiful ultra? Is there a bucket list of ultras that most amateurs should aspire to run?
Again, this is not really an ultra, although I believe that it should be considered as one, but the rim-to rim-to rim on the Grand Canyon is my favorite and likely the most beautiful ultra in the country. Check out the great interview on irunfar of walmsley crushing it https://www.irunfar.com/2016/11/jim-walmsleys-grand-canyon-r2r2r-and-r2r-fkt-report.html there is also a great video of rob krar setting a previous record.
*Who is the GOAT of ultra running?
For long distance on flat grounds it is definitely Yiannis Kouros. Especially with the recent news about Abraham Kiptum, I must say though that I don't know if his numbers are possible without PEDs, and I am not sure if he was ever tested. Sage in his interview didn't talk much about doping although he has been a big advocate of anti-doping. Doping definitely works in ultras. As part of your research, I recommend that you re-read the great article about Hellebuyck and the damning accusations he has against the greatest Comrades runnder of all time: Leonid Shvetsov https://www.runnersworld.com/runners-stories/a22000371/the-confessions-of-eddy-hellebuyck/
Also the skill some of the very early runners - there were big 6 day racers even in the late 1800s - are also incredibly impressive. For example, James Albert breaking the 1000km barrier in 6 days is absolutely bonkers. There are also incredible people around the world who have done incredible things in terms of long distance running although there weren't many historical races - for example the marathon monks of mount hiei in Japan, the lungompa runners in Tibet, and some of the Navajo runners to name a fer.
Also, I want to give a big shout-out to Pete Kostelnick. I don't know if he is the GOAT but his run across america was one of the best ultra performances of all time. Over 3000 miles in 42 days insane - plus he ran in hokas the entire way. You should definitely interview him! Not to mention, his run last year from Alaska to the Florida Keys was bonkers - pushing all his food and water in a baby stroller.
I think Matt Carpenter should also be in the consideration for GOAT even though he mainly only raced in the United States. Matt ran in the Olympic trials and completely dominated the Pike's Peek marathon - up and down Pike's Peek, another iconic race - for a long number of years, and he still has the record at the famous Leadville Trail 100 in Colorado.
*What are the hardest course/world records to break in ultra running?
The recent 100km record is probably the hardest to break, because I believe that it has been challenged by the largest number of people.
The 100 mile record is also quite hard to break, although sadly it seems that there is more than some possibility that Oleg Kharitonov's 11:28:03 may have benefitted from PEDs. The American Zach Bitter has been making some good attempts in recent years.
Ultra courses vary so much year to year due to temperature and snow pack that it is really hard to compare times from year to year. That is part of the reason why I think fastest-known-times may be more impressive, and so I would personally go with the Appalachian Trail FKT.
Karl Sabbe's 2016 FKT on the Appalachian Trail of 41 days, 7 hours and 39 minutes may be the standard to beat in terms of the hardest course and best record in the world.