Prediction of knee joint torque from muscle activity during knee flexion/extension

The relationship between the torque production of a muscle and its EMG signal is, to date, not well defined. The purpose of this study was to investigate the relationship between the knee joint torque and the EMG activity of five major muscles crossing the knee. Rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), semitendonosis (ST) and biceps femoris (BF) EMG activity and knee joint torque were recorded for five subjects using surface electrodes and a BIODEX system, respectively. Data were normalized and averaged for three trials, for each of four speeds. A relationship between torque and EMG was developed for both extension and flexion with r squared values ranging from 0.73 to 0.98.