What happens to the human body during rigor mortis?

During rigor mortis, the primary physiological change that occurs is the stiffening of the body's muscles. This happens because, after death, the biochemical processes in the muscles change, leading to the formation of cross-links between the actin and myosin filaments that are responsible for muscle contraction. Without the usual energy supply from ATP, these filaments remain bound to each other, causing the muscles to become rigid and stiff.

This stiffness begins to set in a few hours after death and generally peaks at around 12 to 24 hours, after which the rigidity starts to dissipate. Understanding this process is crucial in forensic science and medicine, as it aids in estimating the time of death and assessing the condition of the body. The other options do not accurately describe the primary effects of rigor mortis, focusing instead on aspects like cooling or decomposition, which are related but distinct phenomena.