Final answer:
Body weight affects rigor mortis by influencing the rate of onset and resolution due to the muscle to fat ratio. Increased muscle mass, which can result from physical exercise, leads to a more rapid onset and resolution of rigor mortis due to muscle having greater stores of glycogen and a higher metabolic activity than fat tissue.
Step-by-step explanation:
Body weight, especially the ratio of muscle to fat tissue, has a significant impact on the onset and progression of rigor mortis. This phenomenon, which is the stiffening of the muscles after death, can be influenced by the overall composition of the body. Individuals with a higher muscle mass may experience a more rapid onset and resolution of rigor mortis. Muscle is more metabolically active than fat, and it contains larger stores of glycogen, which is depleted to produce energy in the form of ATP during the early stages of rigor mortis. After death, when oxygen supply stops, the body uses up the remaining ATP and does not produce more, leading to the stiffening of muscles.
Furthermore, physical exercise influences body composition by increasing muscle mass and reducing fat, thereby potentially affecting the process of rigor mortis. Exercise has been shown to increase the basal metabolic rate (BMR), which means a person with more lean tissue will continue to burn calories at a higher rate even post-mortem until the body cools down. With a higher amount of lean muscle tissue, the biochemical changes that contribute to rigor mortis, such as the depletion of ATP, may proceed at a different rate when compared to individuals with less muscle mass.