COMPARISON OF INTERSEGMENTAL TIBIOFEMORAL JOINT FORCES AND MUSCLE-ACTIVITY DURING VARIOUS CLOSED KINETIC CHAIN EXERCISES

The purpose of this study was to analyze intersegmental forces at the tibiofemoral joint and muscle activity during three commonly prescribe d closed kinetic chain exercises: the power squat, the front squat, an d the lunge. Subjects with anterior cruciate ligament-intact knees per formed repetitions of each of the three exercises using a 223-N (50-po und) barbell. The results showed that the mean tibiofemoral shear forc e was posterior (tibial force on femur) throughout the cycle of all th ree exercises. The magnitude of the posterior shear forces increased w ith knee flexion during the descent phase of each exercise. Joint comp ression forces remained constant throughout the descent and ascent pha ses of the power squat and the front squat. A net offset in extension for the moment about the knee was present for ail three exercises. Inc reased quadriceps muscle activity and decreased hamstring muscle activ ity are required to perform the lunge as compared with the power squat and the front squat. A posterior tibiofemoral shear force throughout the entire cycle of all three exercises in these subjects with anterio r cruciate ligament-intact knees indicates that the potential loading on the injured or reconstructed anterior cruciate ligament is not sign ificant. The magnitude of the posterior tibiofemoral shear force is no t likely to be detrimental to the injured or reconstructed posterior c ruciate ligament. These conclusions assume that the resultant anteropo sterior shear force corresponds to the anterior and posterior cruciate ligament forces.