I have a 1:28 half-marathon PR, a 3:07 marathon PR, I've twice run 100 miles in under 24 hours, and I can't imagine even more. That said, the marathon WR is 2:

I have a 1:28 half-marathon PR, a 3:07 marathon PR, I've twice run 100 miles in under 24 hours, and I can't imagine even more. That said, the marathon WR is 2:01:39 which is 4:38.39/mile (2:52.98/km). So Sorokin is running about 55% slower than that, or what would be considered an easy pace for an elite marathoner. AFAIK, we have yet to see an elite marathoner transition to ultras. However, there are quite a few elite ultra-marathoners who run marathons. The one I'm most familiar with is Michael Wardian: https://en.wikipedia.org/wiki/Michael_Wardian https://en.wikipedia.org/wiki/Michael_Wardian He's run both a 2:17:49 marathon and finished 15th as Western States (19:32:07). And to be clear: I'm not diminishing Sorokin's amazing accomplishment here. I've run a 24 hour race. I got to 105 miles. I'm just noting what the best in the world are capable of at different distances. Humans are amazingly adaptable. I'm reminded of Howard Schatz’s Athlete series of photographs: https://www.boredpanda.com/athlete-body-types-comparison-howard-schatz/ https://www.boredpanda.com/athlete-body-types-comparison-how... https://howardschatz.com/human-body/athletes/ https://howardschatz.com/human-body/athletes/