Quantifying skeletal muscle properties in cadaveric test specimens: Effects of mechanical loading, postmortem time, and freezer storage

Investigators currently lack the data necessary to define the state of skel etal muscle properties within cadaveric specimens. The purpose of this stud y is to define the temporal changes in the postmortem properties of skeleta l muscle as a function of mechanical loading and freezer storage. The tibia lis anterior of the New Zealand white rabbit was chosen for study. Modulus and no-load strain were found to vary significantly from live after eight h ours postmortem. Following the changes that occur during rigor mortis, a st able region of postmortem, post-rigor properties occurred between 36 to 72 hours postmortem. A freeze-thaw process was not found to have a significant effect on the post-rigor response. The first loading cycle response of pos t-rigor muscle was unrepeatable but stiffer than live passive muscle. After preconditioning, the post-rigor muscle response was repeatable. The precon ditioned post-rigor response was less stiff than the live passive response due to a significant increase in no-load strain. Failure properties of post mortem muscle were found to be significantly different from live passive mu scle with a significant decrease in failure stress (61 percent) and energy (81 percent), while failure strain was unchanged. These results suggest tha t the post-rigor response of cadaveric muscle is unaffected by freezing but sensitive to even a few cycles of mechanical loading. [S0148-0731(00)00301 -0].