A different virus: Heartfire Headcannons!

Page 2: Zombie Headcannons

1: Zombies are slower because of all the extra muscle

Zombies are noticeably stronger as mentioned in the books, so it would only make sense if they had more developed muscles. But unfortunately, the human body the virus possesses, does not have bones strong enough to constantly let the Zombie run around and constantly snap. This makes them slower and is why they always look so disfigured or have limbs twisted at awkward angles.