Introduction: Anterior cruciate ligament (ACL) injury is one of the most common injuries of the knee joint, which also often requires arthroscopic ACL reconstruction. Physiotherapy after ACL injury and reconstruction is a long-lasting and often not completely successful in terms of performance and function of thigh muscles. Low-load ischemic training proved to be an effective method of strengthening the muscles in healthy subjects and it may be appropriate also for use in patients with ACL injury. Purpose: The purpose of this study was to evaluate the effectiveness of the preoperative low-load ischemic training program to improve capacity in the thigh muscle function in subjects with ACL injury. Methods: 13 patients (age 37.5 ± 6.5 years) with an ACL rupture participated in the study. Subjects were assigned into two groups: ischemic group (IS), which performed the low-load ischemic exercise to strengthen the thigh muscles of the injured leg, or placebo-ischemic group (PIS), which performed the same training program but without blood flow restriction of thigh muscles. Before and after completed training program testing of thigh muscles function (Single leg hop test) and performance (dynamometric testing and the EMG measures of the quadriceps femoris muscle activation) was carried out. Results: Subjects in IS achieved a statistically significant major improvement in isokinetic muscle performance of the knee flexors (p60°/s < 0.05; p120°/s < 0.01) and knee extensors (p60°/s < 0.05) and greater knee extensors muscle endurance (p60°/s < 0.05) by comparison with group PIS. The function of thigh muscles improved significantly in both groups (p < 0.001), with no significant differences between groups. As well there was an improvement in the EMG amplitude of the quadriceps femoris muscle activation, namely vastus medialis (p < 0.05) and vastus lateralis muscle (p < 0.05). Discussion and conclusion: The program of low-load ischemic exercise is more effective for patients with ACL injury to strengthen the thigh muscles, especially knee flexors, than the same amount and intensity of the exercise without blood flow restriction of the active muscles. It is also more effective in improving the knee extensors endurance.
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