Do zombies have super strength?
No, a zombie is not stronger than before dying from the virus. However, his hunger for flesh and a total lack of inhibitors/fear give him the unfair advantage of a firm grip, not much different than the pit bull. In the case of undeads, since the body is slowly decaying, their strength will slowly decline and wane after a few weeks. The fast “enraged” zombies will remain healthy probably longer but it depends on the type of virus.
