Does the sequence of onset of rigor mortis depend on the proportion of muscle fibre types and on intra-muscular glycogen content?

We examined the postmortem changes in the levels of ATP, glycogen and lacti c acid in two masticatory muscles and three leg muscles of rats. The propor tion of fibre types of the muscles was determined with NTH image software. The ATP levels in the white muscles did not decrease up to 1 h after death, and the ATP levels 1 and 2 h after death in the white muscles were higher than those in the red muscles with a single exception. The glycogen level a t death and 1 h after death and the lactic acid level 1 h after death in ma sticatory muscles were lower than in the leg muscles. It is possible that t he differences in the proportion of muscle fibre types and in glycogen leve l in muscles influences the postmortem change in ATP and lactic acid, which would accelerate or retard rigor mortis of the muscles.