Electromyography (EMG) is the study of muscle behaviour via electronic means, and is thus a technique fundamental to ergonomics, physiology and biomechanics. This text describes the principles of EMG and its application domains, focusing on anatomy, biology, muscle characteristics, physics, mechanics, EMG signal, noise/artifacts/errors, equipment/devices/techniques, interpretation and computerised data acquisition, and analysis. The book provides a theoretical base, a strategic framework and user experiences.