Contents
Four hours after death, the human body stiffens. This phenomenon is called postmortem concentration and is one of the early signs of death. We explain why a person stiffens after death.
- After death, the life processes in the human body subside one by one
- As a result of hypoxia, cellular respiration ceases, and thus the production of ATP, responsible for muscle contraction and relaxation.
- Therefore, a few hours after death, the body of the deceased begins to stiffen – the muscles remain in contraction
- Assessment of the fracture of the postmortem concentration is one method of determining the time of death
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After death, the body gives clear signals that it has lost its life. Among the early signs of death, we can distinguish precipitation spots, cooling down, drying up of the corpse and the stiffness of the body.
The corpse becomes stiff 3-4 hours after death. This phenomenon is called postmortem concentration – rigor mortis. Scientists have established that the postmortem concentration is associated with blockage of the enzyme systems that are responsible for the functioning of muscles during life. This leads to a permanent contraction of the muscles, which makes the body stiff.
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As Dr. Filip Bolechała, a forensic doctor, explained for Tygodnik Powszechny, muscles consist of fibers forming actin and myosin strands responsible for muscle contraction and relaxation. The energy component of ATP is necessary for relaxation, and after death from lack of oxygen, its production stops: “And when its remaining reserves in the body are used up, the muscles tense and close in the same position” – explains the doctor.
ATP is used to pump calcium out of cells so that the fibers can detach from each other. Therefore, after death, calcium builds up in the bones and muscles and causes the body to stiffen.
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Posthumous concentration “in installments”
Postmortem concentration first takes place in the heart, about 40 minutes after death, the skeletal muscles stiffen later, about 1,5-2 hours. First, small muscles become stiff, e.g. the face and fingers, then the jaws, wrists, and eventually the large joints become stiff. The full postmortem concentration of the whole body is achieved after approx. 3-4 hours. The duration of muscle stiffness depends on the very structure of the muscles, environmental temperature, and the circumstances of death.
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What after post-mortem concentration?
But the body does not become rigid, and the concentration at the point of death eventually subsides – usually after 48-72 hours. This happens after the autolysis and rotting processes begin.
This phenomenon was explained in an interview with Medonet by Dr. Jerzy Kawecki from the Department of Forensic Medicine, Medical University in Wrocław: – When the postmortem concentration subsides, the body becomes flaccid again.
The doctor also explained why the body sometimes looks as if the deceased was trying to “free himself” from the coffin: – The classic position of the corpse in the coffin is the supine position with the hands clasped at the level of the chest. If the burial takes place when the concentration has already subsided, then it is very likely that due to the wobbling of the coffin as it is inserted into the grave, the hands may break apart and fall to the sides of the body inertly. In obese people, this situation is additionally easier, because if the hands are placed on the protruding belly, they can move very easily under the influence of gravity – explained Dr. Jerzy Kawecki.
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Post-mortem concentration and determination of the time of death
One method of determining the time of death is by assessing the fracture of the post-mortem concentration. There is some ATP left in the muscles for some time. Therefore, if we force a dead person’s joint to move, concentration will re-build. But if the ATP reserves already disappear, in the event of forced movement of the joint, the fibers will tear and not be able to reattach, therefore the muscle will not contract again.
Thus, depending on the time at which the concentration is broken, the time of death can be determined. If this is done three hours after death in the upper limb, the concentration returns practically completely. But over time, this muscle capacity weakens and, for example, after eight hours, it will not appear again.