The subject studied the relationship between tissue dynamics caused by Quadriceps muscles movement in the knee extension — flexion state and the signal measured from the EMG sensor. Establishment of force and momentum force equations generated by the muscle groups, EMG momentum and voltage equations. Using the Arduino Uno controller, read the signal from the EMG sensor, and save it to an SD memory card. Use Excel software to process the signal and display the state diagram of the objects when knee articulation in the extension — flexion exercise. The result is the premise for the application of executive control to assist patients recovering lower extremities.