I admit that when it comes to zombie movement, I am a purist. A zombie shouldn’t be winning the 50-meter dash or leaping tall buildings in a single bound – they shamble. Yet, there has been a disturbing trend to provide the undead with almost superhuman agility and speed.
Zombies have primarily been seen as slow moving and lethargic, more lethal as a mob than individually. Romero set the bar for this in his original movies and from one side of the spectrum that makes sense. The undead are reanimated corpses, especially the ones that had to dig themselves out of the grave after 10 years.
Their brain activity is limited and motivated purely by instinct. Their muscles would be atrophied and rotted from their time being truly dead. Also, they would continue to degrade, so eventually they would rot down to nothing but bones. Without muscles, the bones don’t move and that would be a horrifying existence.
When they began making the remakes like Dawn and Day of the Dead, the zombies sprinted about like track stars and did feats of acrobatics that would win gold in an Olympic event — if they had an event called the 100-meter maiming. I have seen zombies run on all fours, climb on the walls and even a newborn zombie booked it like Oprah to an all-you-can-eat buffet.
Once again, I can see how this would have merit as well, at least for the newly dead zombies. While the brain power would still be diminished, possibly even similar to a long dead zombie and be totally instinctual, they would still have strong and healthy muscles only beginning to decay. They could be fast and strong because they would no longer have the pain holding them back. They would be free to stretch their muscles to the limit and beyond, all for the sake of killing, maiming, etc.
As for the acrobatics, if you take away the pain response and override their regular sensibilities with the instinctual need to hunt and feed then it could make sense. They would have the strength to leap long distances and their hunting mentality would make them like any other predator.
In a way, I guess I have to give a little leeway to the acrobatic dead. The newly dead should be fast moving until their decay gets to the point that they become the shambling corpse and then finally a nasty pile of flesh and bone when their muscles give out entirely.
For me, the shambling corpse will always be the appropriate zombie in movies because of what zombies have come to represent. They are the lazy oblivious culture that is so prevalent in the world. They are easily swayed one way or the other, not caring about the world around them or even themselves. They eat, sleep, work, sleep, eat, etc.
They are the sheep that while individually are not a threat and somewhat humorous, in mass they can change the direction of the political and societal landscape through pure apathy and herding. Romero hit the nail on the head in Dawn of the Dead as the zombies all filed to the one place they were familiar with, the mall.