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Development of rigor mortis is not affected by muscle volume
M Kobayashi1, H Ikegaya, I Takase
1Department of Forensic Medicine, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-0033, Tokyo, Japan. koboo@m.u-tokyo.ac.jp
Abstract:
There is a hypothesis suggesting that rigor mortis progresses more rapidly in small muscles than in large muscles. We measured rigor mortis as tension determined isometrically in rat musculus erector spinae that had been cut into muscle bundles of various volumes. The muscle volume did not influence either the progress or the resolution of rigor mortis, which contradicts the hypothesis. Differences in pre-rigor load on the muscles influenced the onset and resolution of rigor mortis in a few pairs of samples, but did not influence the time taken for rigor mortis to reach its full extent after death. Moreover, the progress of rigor mortis in this muscle was biphasic; this may reflect the early rigor of red muscle fibres and the late rigor of white muscle fibres.
Insights
Muscle volume does not affect rigor mortis progression or resolution, contradicting prior hypotheses. Pre-rigor muscle load impacts onset and resolution but not the time to full rigor, suggesting a biphasic process.
Area of Science:
- Physiology
- Biophysics
Background:
- Rigor mortis is a post-mortem stiffening of muscles.
- A prevailing hypothesis suggests faster rigor mortis progression in smaller muscles compared to larger ones.
Purpose of the Study:
- To investigate the influence of muscle volume on rigor mortis progression and resolution.
- To test the hypothesis that smaller muscles exhibit more rapid rigor mortis.
Main Methods:
- Isometric tension measurements were used to quantify rigor mortis.
- Rat musculus erector spinae were dissected into bundles of varying volumes.
- The effects of pre-rigor load on rigor mortis parameters were examined.
Main Results:
- Muscle volume did not significantly affect the progress or resolution of rigor mortis.
- Pre-rigor load influenced the onset and resolution phases but not the time to maximum rigor.
- Rigor mortis progression in the studied muscle exhibited a biphasic pattern.
Conclusions:
- The hypothesis that muscle volume influences rigor mortis speed is refuted by this study.
- The biphasic nature of rigor mortis may be attributed to the differential timing of red and white muscle fiber stiffening.
- Pre-rigor load is a factor in rigor mortis dynamics, but muscle volume is not.