Dynamic mechanical measurements during the life to death transition in animal tissues1

Changes in the mechanical properties of animal tissues with time after death have been frequently observed, and descriptions of rigor mortis for example are numerous. Most previous accounts of mechanical changes in tissues during the life-to-death transition, however, are qualitative. Measurements of dynamic shear compliance vs dead time at room temperatures are reported here for cow gluteal muscle, several samples of rabbit and human cancellous bone, and dog intervertebral disks. In all cases an abrupt second-order transition is observed in one or both components of the audiofrequency complex shear compliance, J∗=J′−iJ″ at 5–6 hr after death; this is considered to be an indication of the life-to-death transition in animal tissues.