Apparently, nobody has talked about this in years...
I disagree with the idea of an activated ability/cooldown timer.
We've already got finely graduated tiredness/windedness stats that are affected by creature attributes.
It should be noted that humans are endurance monsters; you've got no chance of keeping up with a horse at first, but if you have a 40km chase or it involves hills (particularly downhill), you'll get 'em (or get away).
Rabbits on the opposite end of the spectrum are speedy little varmints, but can't run more than about two laps of my backyard (perhaps cross an embark tile) before they putter out, flop over and wait to be eaten by a puppy smaller than they are.
Also, currently running away cures tiredness instead of causing more! (Tired of kicking and punching that unconscious elephant? Run around for a bit and you'll be ready for another bout!)
Suggestion:
Using the combat preferences, or something similar: an option for choosing walk/run/sprint as the desired movement speed.
- Walk would be defined as the combat-move speed that allows normal attacks, parrying, etc
- Run would be the speed at which you do not gain or recover from tiredness/windedness. Given lung damage or very poor endurance, this may be indistinguishable from Walk.
- Sprint would be the maximum speed you can move, falling back to Run when tired/winded becomes critical.
Sprint (and run, depending on the situation) would limit your combat choices to a charge attack (with bonus due to speed) against things in the direction you were last moving. Tumbles and skids as in the new dev log would be likely.
And, ambush predators would naturally use that whenever they can.
I'm not familiar with the raws, but there would need to be a definition for a sliding scale of speed vs efficiency, presumably on muscle tissue.
Modelling real-life Type I, II, IIB muscle tissues could work, if you are allowed to mix them in a creature.
PS:
Pain should also be added to the list of tiredness/windedness for the run speed limit.
Creatures with arrows sticking out of them and leg wounds should not be going full speed indefinitely, or at least without exacerbating the wounds.