VG, Pinto S de S. Isokinetic torque peak and hamstrings/quadriceps ratios in endurance athletes with anterior cruciate ligament laxity. Clinics. 2007;62(2):127-32. PURPOSE:To evaluate torque and the hamstring/quadriceps ratio of the knee of athletes with and without anterior cruciate ligament laxity. METHODS: Twenty-eight male athletes, 19 without anterior cruciate ligament laxity and 9 with anterior cruciate ligament laxity, were evaluated with an isokinetic machine model Cybex 770. The peak torque of quadriceps and hamstrings was compared, and the hamstring/quadriceps ratio on the constant angular speed of 60º per second were also compared. RESULTS: In athletes with anterior cruciate ligament laxity, the peak torque values (right and left knees) of flexors (120 ± 15 and 116 ± 15 Nm) and of extensors (218 ± 36 Nm and 207 ± 26 Nm) were not different than those of athletes without laxity (109 ± 21 Nm and 111 ± 22 Nm; 191 ± 5 Nm and 188 ± 35 Nm). The hamstring/quadriceps ratio of athletes with laxity (right: 57 ± 6% and left: 56 ± 8%) did not differ from those without anterior cruciate ligament laxity (right: 58 ± 9% and left: 58 ± 7%). CONCLUSIONS:The anterior cruciate ligament laxity of long distances running athletes did not significantly alter the peak torque of flexors and of extensors or the hamstring/quadriceps ratio. KEYWORDS: Isokinetic torque. Knee. Anterior cruciate ligament. Laxity. Athletes. INTRODUCTIONTorque is the rotational effect of force generated by a single muscle or group of muscles in relation to the considered joint.1 Because the term force is basically a linear entity, in this study when referring to muscle strength, the term torque was conventionally used. The term strength refers to the tension that a muscle or group of muscles exerts against a determined resistance.2 The unbalanced condition of strength and the hypotrophy of the flexor and extensor muscles of the knee joint are muscle malfunctioncausing factors that alter joint stability, predisposing athletes to injury. [3][4][5] The muscular torque of the quadriceps and hamstrings, as well as their torque ratio (H/Q), is usually evaluated by the isokinetic test. 6 The H/Q ratio is used both clinically and in the laboratory as an indicator of the strength balance between the knee joint muscles. 7 The H/Q ratio is conventionally calculated by dividing the maximum values of the flexion by the maximum values of the extension of the knee joint in angled speed and determined contraction modes. 8It is difficult to determine whether the hamstring weakness, the quadriceps weakness, or both are related to the knee injuries, or if muscle weakness is a consequence of the injury.9 Evidence suggests that highly developed quadriceps muscles contribute to a decrease of the co-activation of the hamstring antagonists, thus increasing the susceptibility for anterior cruciate ligament injury. The anterior cruciate ligament (ACL) is the primary ligament that limits the anterior translation of the tibia in relation to the femur. Subjects with ACL injury de...