|The following is based on Fallout Tactics and some details might contradict canon.|
Your character has been winded, and cannot run.”
A character can be winded from a Critical Hit to their torso, received in either hand-to-hand or ranged combat.
Fallout 3 and Fallout: New VegasEdit
Characters can be become winded by having their torso crippled, making them flinch more from damage taken.