Development of rigor mortis is not affected by muscle volume

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 t he 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 d eath. Moreover, the progress of rigor mortis in this muscle was biphasic: t his may reflect the early rigor of red muscle fibres and the late rigor of white muscle fibres. (C) 2001 Elsevier science Ireland Ltd. All rights rese rved.