Running a Marathon?

Hello!

I've taken a look at the rules for movement, and they seem a little... limited. In real life, the best humans can run a 10k in 20minutes, or a marathon in like 2 hrs. Seems like a player with 18 CON should be able to match that, if not exceed it. This IS fantasy, after all.

What Houserules do people have for this? I have a 15th level ranger (16 CON )who just used Tree Stride + running to get 15 miles through the woods in twenty minutes. My reasoning at the time was that tree stride gets you 15*3000ft, and the winning times for the 10k I looked up were around 20min.

Thoughts?