Feats

Run [General]

Benefit: When running, you move five times your normal speed (if wearing medium, light, or no armor and carrying no more than a medium load) or four times your speed (if wearing heavy armor or carrying a heavy load). If you make a jump after a running start (see the Jump skill description), you gain a +4 bonus on your Jump check. While running, you retain your Dexterity bonus to AC.

Normal: You move four times your speed while running (if wearing medium, light, or no armor and carrying no more than a medium load) or three times your speed (if wearing heavy armor or carrying a heavy load), and you lose your Dexterity bonus to AC.

Source: SRD 3.5 Feats