Tibiofemoral Joint Kinetics During Squatting With Increasing External Load

Context: There is limited information about the effects of increasing load while squattingObjective: To quantify tibiofemoral jointkinetics during squattingwith variable loads. Setting: Research laboratory. Participants: 20 male students. Intervention: Tibiofemoral jointkinetics and electromyographic (EMG) activity of four involved muscles were determined by recording the half squatwith variable external loads. Main Outcome Measures: Tibiofemoral jointforce and external moment components and EMG activity of four involved muscles. Results: Throughout the exercise, a posterior direction for the antero-posterior shear force and a net extension for the external moment were observed. They increased with knee flexion reaching peak force of 29% of the subject body weight (BW) and moment of 88Nm (without external load). All force and moment components and muscle activities increased as the external load increased. Conclusion: These findings suggest that half squatmay be safe to use for quadriceps strengthening with very low potential loading on the anterior cruciate ligament (ACL). Our data can help clinicians choose the appropriate external load. Strengthening exercisesthat incorporate the use of barbellsare considered an integral part of sports training programs and knee rehabilitation. In general, emphasis is put on the muscular aspect, whereas the articular aspect is often neglected even though these exercises may induce important joint mechanical stress which can worsen the syndrome of articular pathology or even cause serious injuries if they do not respect the physiological limits of ligamentous and/or articular structures. 1,2 The lack of information about the forces carried by the ligaments or ligament grafts during the different strengthening exerciseshas led to disagreements between specialists as to what constitutes a good rehabilitation program. 3 The squatexercise is a classic multiple-joint exercise that has become an important component of lower limb strengthening programs in physical therapy and in