3. Security Guards - Time on their feet and especially those on duty during graveyard shift. I mean it is not easy staying awake at night. This will come handy when ultra races involve night time running. On endurance, same as farmers.
4. Mountain Guides/Trekkers - You cannot beat this people on mountain hiking and leg strength. Those power walks, uphill and downhill climbs will be very helpful during trail running. Some of them even wear slippers! As runners, aren't we overdressed?
6. Firemen - On heat tolerance, nothing beats these guys.
8. Psychiatrists/psychologists - Basically for their erudite persuasion to keep them from quitting when they hit their lowest of lows. After all, ultrarunning is not only physical but mental as well. They sorely need to be physically fit to undertake a race this long though.
9. Chefs, Waiters and Bakers - They are up on their feet for long hours while they prepare our favorite food to fuel us to finish a race, i.e. if you have money to burn. I bet they need to work on their endurance also. They have also properly learned the meaning of heat adaptation for being exposed to heat in the kitchen.
10. Bus Vendors - An epitome of ultrarunners. Fast and daring. I mean they run after a bus, hold onto the rail and get inside just to peddle their goods all on a busy street/highway and while the bus is moving! And they do it all over again. Talk about guts. Only I wonder if they could do all that running for more than 42.2k.
11. Park Rangers - Countless hours out there. Good for trail running. But endurance? I am not sure.