Well a few things come to mind here .....
My MCMAP instructor always told me .... "Never engage an enemy at arms reach whom you can safely engage at a distance!"
In other words ... it's always better to fire or fight, but never flee!
On the other hand ....
In an urban CQC setting a person must be able to sprint down long alleys ... roll over 6 foot fences with minimal effort ... kick down doors ... and be able to run another mile when it's all over.
I've seen some of the biggest, baddest musclebound Marines get winded after a 2 mile hump. Then I've seen some of the fastest sprinters who were unable to roll a fence or short wall.
It's my opinion that in a CQC Urban setting you just need to be lean and mean. In other words .... built like a baseball player with the lungs of a Cross Country runner.