Effect of immobilization in a lengthened position on mechanical properties of the Achilles tendon in growing rats

The purpose of the study was to examine the effect of long-lasting immobilization in a lengthened position on mechanical properties of immature tendon in a rat model. One hindlimb of growing rat was immobilized for two weeks with the Achilles tendon in extension. Tensile failure test was performed post-mortem at a rate of 10 mnimin without any preconditioning. Immobilization caused reduction of the elastic range of deformation both considering force and extension. The stiffness of tendons was decreased, especially at small strains in an inelastic 'toe' region. However, the plastic range was broader and the maximum load similar compared to these of normal tendons. It was revealed that immobilization, even under constant tension, changes significantly mechanical properties of tendons in the range of small strams encountered during physiological loading. The changes may alter the behaviour of a joint after restoration of a normal activity.