Tensile strength, relaxation and mechanical recovery in rat skin as influenced by maturation and age.

Several mechanical parameters were measured in skin strips of rats at various ages (1, 2, 4, 12 or 24 months). Ultimate load and tensile strength increased during the maturation process and reached a maximum at 12 months. In old animals (24 months) a decrease of these parameters was noted. After various preloads relaxation was measured. Relaxation could be described mathematically as a function of logarithm of time. The relaxation coefficient decreased during the maturation as well as during the ageing period. After unloading up to 1/5 initial load mechanical recovery was measured. Mechanical recovery was increased depending on age during the whole life span. It is concluded that various components of viscoelatic behaviour are influenced differently by the maturation and the ageing process.