I don't really get why we got a sprint function when we could already run...And running speed was attribute-based,could be buffed up with magic etc...Very weird...
Standing still - No movement, restores fatigue at good rate.
Walk - Slow movement, doesn't waste fatigue, but will regenerate it at slow rate.
Run - Medium movement, slow fatigue waste.
Sprint - Fast movement, fast fatigue waste.
Running and walking can be used inside battle while maneuvering yourself around the enemy and avoiding his attacks, while sprints are used for 'oh, crap, crap, crap, run, run, run' situations (ie. dragon chasing your ass while breathing nuclear bombs) or any situation where you need quick bursts of speed.