World War Z

[Watchman]

And are you telling me they'll be able to act as if any broken bones they had, weren't, and major muscle clusters they might've had gnawed off, weren't ? The way they invariably stumble and drag for example damaged legs rather speaks against that.

I'm not going to go into the variously stupid explanations for the zombification process itself and the source of their motive power (although an obsession with eating would suggest the presence of metabolism and hence need for nutrition, all in all a measure of what can be termed "life"), but if it's anything short of outright demonic possession or something similarly grossly supernatural (in which case the buggers might as well grow ten foot tall and fart fire, all the bets being off) physical damage will slow them down even if they do not as such pay it any heed.
A missing leg is a missing leg, and you're not going to be able to stand on it period.

Which brings us back to the major logical problem with the critters using their potential new recruits as their main source of sustenance, whatever benefit they now may derive from that. Not the most brilliant way to procreate/replenish casualties, I'd say.