Magnetomyography: magnetic fields around the human body produced by skeletal muscles

Measurements of the magnetic fields from skeletal muscles, called magnetomyograms (MMG's), have been taken in a heavily shielded room with a superconducting magnetometer. These magnetic fields appear to be produced by the same currents in the volume conductor, associated with muscle action potentials, which also produce the surface electromyogram (EMG). Unlike the EMG, however, the MMG can readily detect slowly changing or direct currents. The MMG's, which were taken at locations near the elbow and the palm of the hand, are shown along with their frequency spectra.