The Limit of Adapting to Exercise Loading in Rat Patellar Tendon

Abstract

Male Wister rats age 9 weeks weighting 236-280 g were jumped 300 times. After these animals were sacrificed, tensile tests were performed on patella-patellar tendon-tibia complexes. There were no significant differences in the average mechanical properties of patellar tendons between jumping and control groups. In 60 percent (3/5) of the tendons of jumping group, the mechanical properties did not change. In the remaining 40 percent (2/5) of the tendons, on the other hand, the tensile strength and tangent modulus were remarkably smaller than those of control rats. Our previous study demonstrated that in vivo tension in the tendon during jumping increased to 220 percent of that of normal running in a cage. These results indicate that patellar tendon can not adapt if tension exceeds 220 percent of normal level.