Some argue that the undead can't run. It makes sense to me that freshly infected would have the same speed and range of motion they did prior to infection. Where as a more advanced infected would be slower, more lumbering because of tissue death and rigor. What's your take?
I agree that they will be fast when first infected and that speed and not to mention strength will slowly degrade over time due to the fact that musles tear due to on going use but even so its best not to stick around to find out.