Development and Application of an Apparatus for Continuous Measurement of Muscle Extensibility and Elasticity Before and During Rigor Mortisa,a,b

Abstract

SUMMARYAn apparatus was developed to study the extensibility and elasticity characteristics of muscle fibers before and during the onset of rigor mortis. A variable load (weight) was applied to a muscle specimen held in a chamber under controlled conditions maintained by a thermostatically regulated cartridge heater, cooling coil, and gas inlet. A solenoid cell, energized by a cyclic timer, was used to release and apply the load in a direction longitudinal to the vertically mounted specimen. A lever attached to the specimen‐loading, system transmitted the extensibility and elasticity of the specimen to the armature of a differential transformer. The output voltage, from the secondary transformer winding was directly proportional to displacement of the armature. This AC output signal was rectified and transferred to a DC recording microammeter. The time course of rigor mortis was not influenced by loading and unloading interval or size of muscle strip, and was found to be temperature‐dependent, being prolonged as temperature was decreased. The white fibers of the semitendinosus muscle were found to have a considerably longer delay phase than the red fibers. The relations between the time course of rigor mortis and the ultimate properties of the muscle were discussed.