19. Live muscle fibers slide back and forth After death, muscle fibers become locked in a flexed position

20. ObservationApprox. Time Scale The body is at its most rigid stateJust over 2 hours No visible signs of rigor Less than 2 hours or more than 48 hours ago Stiffness generally disappearsAfter 36 hours

21. factorEventEffectCircumstances TemperatureColdInhibit rigorSlower onset an progression of rigor HotAccelerate rigorFaster onset and progression of rigor Activity before deathAnaerobic exercise Accelerates rigorLack of oxygen to muscle, build up of lactic acid Slows rigorFully oxygenated muscles exhibit rigor more slowly sleep Body massObeseSlows rigorFat stores oxygen ThinAccelerates rigorBody loses oxygen quickly

23. State of ContentsTiming of Death Undigested food present in the stomach Zero to two hours after the last meal Stomach is empty, but food found in small intestine Death occurred at least four to six hours after a meal Small intestine is empty; waste found in large intestine Death occurred 12 or more hours after a meal

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