From Chapter 5 of the rulebook:
Contrariwise, it's more difficult to hit a target that's moving very quickly, or if the attacker is moving very quickly itself; the attacker takes a -1 penalty for every 6" in the speed of whichever unit is moving the fastest. The exception is when the attacker and target are moving directly at one another, in which case this penalty is ignored.
My comment was referring to this. Sprinting minifigs typically move faster than 6". Therefore, targeting them should incur that "fast movement" penalty as long as their totaly speed is 6" or greater.