Factors influencing quantified surface EMGs.

Isometric flexions of the elbow are studied in man. For the three joint angles studied, the torque, the surface EMG of the biceps brachii muscle, and the quantified EMG are recorded. The EMGs are picked up by means of bipolar electrodes located in such a way as to vary the interelectrode orientation, the interelectrode distance and the position on the muscle. Longitudinal placements collect stronger signals that transverse ones. Under certain conditions, the magnitude of the quantified EMG depends on the distance between the electrodes, and on their location on the muscle. The results are discussed in terms of conduction volume and detection volume.