What we’ve come to regard as the classic Romero Zombies are slow moving flesh-eaters that shamble about the countryside clumsily stalking whatever humans might be unfortunate enough to stumble into their paths. People have joked about these things being so slow that it’s silly no one can get away from them. The trick with them is that they may be slow, but there are a lot of them. You can’t possibly take them all out before they get you.
In my thinking, don’t make any assumptions. Assume they are all high-speed runners and if they turn out to be slow all the better. This zombie is a shuffler. In his case, he’s going to be relatively slow moving regardless. These zombies have some sort of damage to their legs that cause them to shamble and shuffle along at a relatively slow pace. Again, take caution here. Assume they are fast movers anyway just in case. They might be shuffling along more slowly but when riled many zombies have shown themselves to be pretty terrifying. Even the slow ones.