In backyard ultras, where competitors keep running until they can no longer maintain a pace of approximately 4 mph, the male record is 50% longer at 450 miles than the female record of 300 miles.

Even in endurance racing, men outperform women as a rule. It’s true that women do occasionally win coed races, but that’s not common.

You’re describing the backyard ultra. The male record is 450 miles over 4.5 days. The female record is 308 miles over 3 days.

The men’s world record marathon time is 9% faster than the women’s. That’s significant. The male runner would finish over two miles ahead of the female runner.