Magnetomyography

Magnetomyography (MMG) is a technique for measuring the magnetic fields produced by the electrical activity of skeletal muscles during contraction. These magnetic fields arise from ionic currents in muscle fibers and are extremely weak, requiring highly sensitive magnetometers. MMG is related to electromyography (EMG), which records electrical potentials, but MMG directly detects magnetic signals, which can be less affected by tissue impedance and electrode contact.

Measurement is achieved with various sensor technologies. Early MMG used superconducting quantum interference devices (SQUIDs), which require cryogenic cooling. More recently, room-temperature sensors such as optically pumped magnetometers (OPMs) and other compact magnetometers have enabled more portable MMG implementations. Sensor arrays and magnetic shielding are often employed to improve spatial localization and reduce ambient noise.

Applications of MMG include neuromuscular research, clinical diagnostics, and control of assistive devices. In prosthetics and human–machine interfaces, MMG signals can be used to decode intended movements, potentially in combination with EMG. MMG may offer advantages for detecting activity from deep or difficult-to-sense muscles and in scenarios where skin-electrode contact is challenging.

Challenges in MMG involve the very weak signal strength, sensitivity to movement, and susceptibility to magnetic interference, requiring advanced signal processing and calibration. Standardization of measurement protocols and validation against established methods remain areas of active work. Ongoing research aims to improve portability, reduce cost, and integrate MMG with multi-modal sensing to enhance reliability and utility.