Sex Differences in Participation, Performance and the Age of Ultramarathon Runners An American group has studied how the difference between men and women in ultra-based developed in terms of ranking and participation.They examined 20 races from 45 to 160 km. The men were faster than the women.The difference was the deepest over 100 km and the greatest over 45-50 km.The fastest men were younger than the fastest women. The difference between the sexes rose with ranking, was the deepest in the winners and higher at the runners in the 10th place.
The difference between the sexes was the highest when fewer women were at the start, this was mostly over 80 km and less than 160 km. The interesting work is read below https://pubmed.ncbi.nlm.nih.gov/26561864/