Which of the following factors does NOT significantly affect the rate of onset of rigor mortis?

Explanation

## Factors Affecting Rigor Mortis Onset **Key Point:** Rigor mortis onset is influenced by metabolic, environmental, and physical factors, but NOT by intrinsic characteristics unrelated to muscle physiology or post-mortem conditions. ### Factors That Accelerate Rigor Mortis 1. **High ambient temperature** — increases enzymatic activity and ATP depletion 2. **Physical exertion before death** — depletes muscle glycogen and ATP stores, accelerating rigor 3. **High muscle mass** — more ATP available, but larger muscles stiffen more visibly once rigor sets in 4. **Fever or sepsis** — elevated metabolic state before death 5. **Electrolyte abnormalities** — affect muscle contractility ### Factors That Delay Rigor Mortis - **Low ambient temperature** — slows enzymatic reactions - **Starvation or cachexia** — reduced muscle mass and ATP reserves - **Drowning** — rigor may be delayed or absent due to muscle relaxation from hypoxia ### Why Hair Colour Is Irrelevant **High-Yield:** Hair colour is a genetic trait determined by melanin content and has no bearing on muscle physiology, ATP metabolism, or post-mortem biochemistry. It is a **phenotypic distractor** with no pathophysiological link to rigor mortis. **Warning:** This is a common exam trap — students may confuse demographic characteristics with physiological factors. | Factor | Effect on Rigor Onset | Mechanism | |--------|----------------------|----------| | High temperature | Accelerates | ↑ enzymatic activity | | Low temperature | Delays | ↓ enzymatic activity | | Pre-mortem exertion | Accelerates | ↓ ATP stores | | High muscle mass | Variable | More ATP, but larger mass | | Hair colour | None | No metabolic relevance |