Local Movement
While exploring an area, you can measure your local movement in feet per minute if a round-by-round accounting of actions isn’t necessary. You can walk or hustle without a problem on the local scale, and you can run for a number of rounds equal to your Constitution score on the local scale without needing to rest. After that you must attempt a Constitution check (DC = 10 + 1 for each previous check) each round to continue running. When you fail this check, you must stop running. Once you have run to your limit, you must rest for 1 minute (10 rounds) before running again. During a rest period, you can move no faster than you can for a normal move action.
Source
Core Rulebook pg. 257