A DICE developer (DarkLord7854) has confirmed on the MordorHQ forums that using the armor perk in Battlefield 4 will cause you to run and sprint at a slower speed compared to how fast you normally run and sprint.
He said this in response to questions about the game balance, as the perk is—after all—one of the few that can actually decide whether you live or die in a gunfight.
It's curious to see whether the implementation of this perk will spark an arms race that will see each and every player donning extra armor to soak up more damage. Hopefully, whatever bonuses provided by the perk will be offset by the run and sprint penalties.
Battlefield 4 is set for release on PC, Xbox 360, PlayStation 3 on October 29, followed by release on XBox One and PlayStation 4 whenever those platforms launch.