I havent ran a marathon (did do a half in the Army) but did once do a 34 mile ruck march, with full body armor, weapon, Kevlar helmet and a 45 lb ruck sack. Up mountains in Germany, at 15 min mile pace. Shit was easily the worst thing ive ever done. Feet are still slightly fucked to this day...
And to top it off, we did a ten mile Battalion run two days later.
You people can talk all the shit you want but that week was terrible. So many people quit too. At least I knew I wasn't weakminded after that