Which of the following best describes the order of muscle stiffening in rigor mortis?

• A. From head to feet
• B. From feet to head
• C. Random order
• D. Only facial muscles then others

Answer: (A)

Rigor mortis progresses in a downward sequence because after death the lack of ATP prevents the detachment of actin-myosin cross-bridges, causing muscles to lock in place where ATP depletion occurs first. The face and neck muscles are usually the first to stiffen because they are smaller and have high metabolic activity, so they run out of usable energy sooner. From there, the stiffness spreads to the trunk and then to the limbs, effectively moving from head toward the feet. Temperature matters too: warmer environments speed onset and cooler ones slow it, but the downward progression remains the typical pattern.