As per started in another thread, adding a fatigue stat has some interesting ideas. Basic idea fatigue is a stat, that you ideally want low. You get fatigue by doing strenous things (swimming, flying via skill, attacking, moving a lot). You lose fatigue by resting - this can basically be measured by the character having an action and not actually doing anything. Certain magic potions could also reduce fatigue. I'd suggest that movement speed should be redone under such a system - movement speeds would vary less, but that amount of fatigue you gain by moving is dictated by how much stuff you are carrying. If not carrying much, you wouldn't get much fatigue - thus, a lightly equipped person could run around all day and not have to rest much. If you're near you wait limit, you'd get fatigue pretty often. Running isn't covered special here - it would fall under movement, but that fact you move whenever you can when running basically means you'd never be resting at all, thus only gaining, never losing. For certain skills, if your fatigue was too high, you could no longer use that skill (have to stop flying, may drown if swimming, etc). Your max fatigue should perhaps be based on constitution and maybe level (don't get fatigued as much at higher levels). for the normal case of just attacking/running around, one idea is when fatigue gets too high, your speed starts to go down, but at the same time, you start losing fatigue (in a sense, game is enforcing idea that you have to slow down). One way to handle this might be that if fatigue is so how, player doesn't get as much speed as they should, but loses some fatigue, anyways, just random thoughts.