The creature moves somewhere else within its MOV range. To Sprint (1 APS), a creature must have performed a Move (1 APS) in its turn. This action can be repeated infinitely as long as APS and STA allow it.
In practice this Regular Action allows for doubled movement, though at the cost of scarce APS which could be spent doing other things, such as firing at the enemy.
Each Sprint (1 APS) costs 1 STA.