Electrical potentials are generated by muscle when there is movement. This Signal can be pick up by electrode to form EMG. For my Final Year Project, I did an amplifier and signal conditioning circuit for EMG. Attached below is the schematics for the Amplifier.

Disposable surface electrode are used to pick up the signal. The amplitude of the signal pick up is low, so amplification is needed to measure the detected signal. A differential amplifier is needed because of the high CMRR. 2 electrodes are connected in between the region of interest and the ground electrode is connected to a reference point. A driven feedback is implemented in the design to improve the signal quality. 2nd order active low pass and active high pass are used to further amplify the signal and filter off the unwanted part of the signal. As the design uses single supply, a 5v to -5v converter is used to power the active amplifier. Isolation amplifier and supply isolation is added as some basic safety implementation in the circuit.