Purpose: Quadriceps muscle strength after anterior cruciate ligament reconstruction is greatly reduced. Finding a solution to prevent the loss of strength is important. The purpose of this study was to investigate the effect of eight weeks concentric cross exercise on the quadriceps muscle strength in men after anterior cruciate ligament reconstruction. Methodology: Twenty patients with anterior cruciate ligament tear with an average age of 22.02±1.55 years and mean weight of 71.7±7.15 kilograms were selected as volunteers, and were divided into two groups: experimental group and control. The experimental group in addition to physiotherapy, performed eight weeks concentric cross exercise with uninjured leg, three sessions per week and each session 20 minutes. The control group just received physiotherapy. Before three days of ACLR and After 9 weeks and performing 24 sessions of cross exercise, Isometric strength of quadriceps muscle in both groups at 60 degrees of flexion in both of legs by Isokinetic BIODEX system were also measured. Data were analyzed by paired and independent samples t-test at a significance level of p<0.05 Results: The results showed that following eight weeks of concentric cross exercise, the quadriceps muscles strength in uninjured leg in the experimental group was significantly increased (P=0.002). Also, after reconstruction of the ACL, the amount of reduction in quadriceps muscles in the experimental group was significantly lower than the control group (P=0.001). Conclusions: Performing concentric cross exercises can have positive effects in reducing the amount of strength. These exercises can increase strength in uninjured limb and also prevent strength reduction in the limb which underwent the surgery

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