Discussion
multiple injury, ACL re-injury
The purpose of our study was to investigate the effects of eight weeks of simple core stability training on improving knee kinematics, hip strength, and trunk endurance in male athletes who had undergone ACL reconstruction and completed conventional post-operative rehabilitation. The finding of this study showed that eight weeks of core stability training resulted in a significant change in core muscle endurance, knee kinematics, and isometric hip muscle strength (except for hip extensor strength) between the pre-test and the post-test (Improving the efficiency of core muscles to stabilize trunk at different planes can be effective in reducing the risk of non-contact ACL injury in athletesDue to the high rate of ACL re-injury, tertiary prevention programs should be designed which are applicable in different places and can be done in a limited amount of time so that they do not interfere with the main training of sports teams. According to the results of this study, it is suggested that the proposed training protocol be used in the daily warm-up program of athletes because these exercises (which are a selection of effective core stability exercises) can be performed in a short and limited time. However, further RCTs with sufficient follow-up should investigate if enhanced core muscle strength and endurance can really contribute to reduced re-/injury risk reduction.One of the limitations of this study was the lack of comparison of injured and healthy limbs of athletes, which is suggested to be considered in future studies. Also, the absence of a control group consisting of non-injured athletes was another limitation of this study. Thus, further studies are needed to compare ACLR athletes with non-injured athletes. The present study was performed on ACLR athletes with hamstring tendon autograft and the results are generalizable to this population. In addition, these results may vary in athletes with concurrent ligament injuries. Hence, it is recommended that multiple injury studies be conducted. Finally, further studies with sufficient follow-up should investigate whether increasing core muscle strength and endurance can really contribute to reduced re-/injury risk reduction.