Generally speaking, zombies in popular culture take on one of two forms:  1) the slow, lumbering zombie, or 2) the fast, agile zombie.  Each holds Zombie Rigor Mortis Progressioncertain dramatic advantages for the filmmaker, but which is a better representation of the reality of zombiism as manifested in actual human beings?  One prominent theory is that it’s both.

Rigor mortis begins to take hold about 3 hours after death, and lasts about 48 hours.  It follows a clear progression and regression curve, with full rigor being gradually reached at the 24 hour mark, then dissipating at the same rate until completely gone.

It is widely believed that the undead deteriorate much more slowly than the simply dead, due to chemical reactions in the brain and body that have a result similar to embalming fluid.  But, deterioration does happen.  Therefore, the time frame for onset and resolution of rigor may be delayed in a zombie, but it will surely occur.  So one theory of zombie ambulatory speed is this:

  1. When a zombie awakens immediately after death it shows no sign of stiffness, and is as fast as it was in life.
  2. As rigor mortis begins to take hold, the zombie gradually slows to a shamble – the “classic” zombie gait.
  3. Once the zombie reaches the height of rigor it is completely stiff, lying on the ground and unable to move.
  4. As the stiffness subsides the zombie rises and begins shambling as it did during the rigor progression.
  5. At the resolution of rigor the zombie is again able to move as fast as if it just died, with no stiffness whatsoever.

If this theory holds true, be prepared to face zombies of all shapes, sizes, and speeds.



  1. This to me is a very scary idea. And it increases the need for stealth speed of ur own and security cause it also means they will be just as wroung or stronger. Than they were in life

  2. Muscle physiology is absolutely dependent on aerobic generation of cellular energy, along with maintenance of a segregated source of intracellular ionic calcium. Sustained contraction, or Rigor, is caused by the uncontrolled release of this calcium throughout the muscle cell. Once this happens, the calcium does not magically return to its cellular storage caches to be used again. In essence, the body upon death, will rigor, and then relax, but the muscles can never contract again as there is no more calcium stored for future use. Hence, the colorful chart provided by the author has no basis in real human or cellular physiology and is completely meaningless.

  3. just a thought, i dont know if it has any basis in fact, but in return of the living dead the mortitian says that an old trick in funeral home to prevent (or lessen) rigor mortis is simple to move the limbs. since we dont know what will cause the zombies isn’t it practical to assume that (if this trick is based in fact) the zombies wont go through rigor because their limbs will be in motion? any thoughts on this?

  4. i personally believe zombies will be able to run at pre-death speed because for the virus to control a zombie they still have to maintain normal functions to keep the brain alive. this includes breathing and a beating heart. also if a zombie is going to move at all it needs to maintain these functions. i dont think zombies would decompose at all, with a beating heart and breathing and what not, it would still go through cell replication also. zombies would be just like humans but with a lack of brain functions, the only way they could actually move and not go through normal functions is if magick were the cause which would allow them to eventually become living skeletons. this also brings the fact tht zombies probably couldnt survive if you cut it in half

  5. If biology is biology, then that biology could very well allow for a post rigor zombie to move as natural as its able.

    I don’t really agree with the whole rigor mortis deal, but as this is all hypothetical, it could very well be that whatever makes humans into zombies, could very well allow for this to happen.

    Biologically, I don’t think the zombies would ever truly enter into a full rigor mortis state; as I don’t see whatever made the zombies becoming dormant enough to allow rigor mortis to happen. But that’s my theory, and hope. I hope we never have to deal with fast zombies.

    And Taylor, do you know how long it takes a body exposed to air to come to the state you are saying? I don’t think in a matter of a day and a half, the flesh is just not going to be decayed THAT much. Atleast, that is my guess, as I have no clue how long it takes either.

    • Do you know what happens after Rigor Mortis? After Rigor Mortis, parts of the muscle, in layman’s terms, just stop working. That is why the body can move again, the muscle stops working, which leads to the ability to move it around without a problem. But at the same time, I don’t think that Rigor Mortis would happen in the first place, at least not to most of the zombies–think about it. Rigor Mortis is caused by a lack of ATP, energy. ATP is obtained by both breathing and breaking down sugar, the former being much faster, but results in much less ATP; therefore, if a zombie kept ‘eating brains’ then it would get enough sugar to produce ATP. This would result in a zombie that doesn’t go through Rigor Mortis, at least not until it goes without brains for long enough

      • Agreed. Actually, after the resolution of Rigor Mortis, the muscles cannot work any more. This is because Rigor is actually caused by the indiscriminate release of Calcium into the muscle cell. Calcium is normally kept segregated and held in reserve until the muscle gets a signal from the brain; then it is released, and by biochemical action on the muscle fibers itself, causes the contraction of the muscle. It is then removed and stored again, awaiting the next nerve signal trigger. However, once a cell begins to die; the lack of biological energy (ATP) causes the cell lose its ability to segregate Calcium. The previously stored Calcium is then released wholesale into the muscle cell, causing it to contract in a sustained manner (ie. rigor). The effects last until the muscle fibers break down and calcium dissipates. Note: since there is no energy to take away and store Calcium again for future use, in effect the muscle would relax from rigor, but would never be able to contract again. Hence, this theory as offered by the author, has no basis in actual real world human physiology. Of course, we can always say that in Zombie make believe physiology that it can happen. But that’s all it is; make believe.

      • Buck, you assume the dead flesh is able to break down the “brains” they eat. However, if as in Resident Evil, the zombies are not in fact eating and digesting the brains but in fact are just chewing and swallowing but unable to digest the cranial tissue, then they would be unable to replenish their depressed ATP production and thus your theory gets shot right into the waste bin. Just because a creature can chew something does not mean they can digest it.

  6. I agree. I don’t care what kind of chemical reactions are going on in a zombified body, biology is biology. Rigor Mortis is simply decay. And once the so-called “effects” are relieved, the remaining muscle and tissue is little more than rotting meat and has neither the integrity or elasticity of its former state that would be needed to be used at a high-paced rate. If a post-rigored zombie were to try and run, its legs would fail and it would fall on its face. The mere fact that it could stand in the first place is quite a feat in itself.

  7. you’re telling me that a corpse 31 hours removed from flowing blood and a beating heart isn’t going to be rotting and decaying? Flesh will be falling from bone, there is no way that zombie will be able to move near as fast as it could when it was a person. your logic is flawed.

    • within 36 hours, the neck, abdomen and shoulders have already turned green. the hair and fingernails have begun to fall off, the face is bloated and the skin is blistered. this is, of course, not incorporating things like bacteria, insects, etc. which would speed up the rate of decomposition.

      • I think everyone here is forgetting a rule on Zombies.

        If a Zombie is undead, that means they don’t die right? They are the opposite of dead while not quite working as a human would.

        The ligaments, muscular skeleton, etc should function on a basic level at least. And being like someone that has had a stroke, can relearn abilities they have lost. If they have relearned to sprint 100 miles a second then hey its all on them. But if you don’t want to keep your package ready to fight those type fiends, it just means I only need to stay ahead of you.

        However, even if you stand by your idea that the human body stops growing at death, check out hair and nail fiber information. Usually the human body doesn’t throw the switch on those, and they will continue to grow (if unhindered) for about 7 days after death.

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