[The effect of exercise on the normal and reconstructed anterior cruciate ligament in rabbits]

The effects of exercise on the biomechanical properties of the normal anterior cruciate ligament and bone specimen were investigated in two groups of rabbits: the one group with seven rabbits aged 7-8 months and the other with nine rabbits of 13-14 months. Four weeks of exercise produced significant increases in the maximum failure load, total absorbed energy to failure and stiffness in group of younger rabbits, but these changes were not seen in the older rabbits. Exercise effects on the remodelling of the reconstructed ACL were further studied in the two groups of rabbits, by observing macroscopic, histological, and biomechanical changes. While histologically normally structured ligament-bone junctions were seen partially in all the specimens, the specimen of the group with four weeks of exercise after 21 weeks after reconstructive surgery, showed a significant increase in stiffness of the reconstructed ACL. Macroscopically a glittering appearance was seen more frequently in the reconstructed ligament when compared to that of a cage-confined non-exercised group of rabbits.