MMG vs EMG: what are the differences?

Surface electromyography (EMG) measures the electrical activity of muscles; it is the laboratory reference. Mechanomyography (MMG) measures their mechanical vibrations; it requires no skin preparation and is better suited to long measurements in the field. Here are their differences, point by point.

When it comes to measuring muscle activity and understanding how our muscles work, two techniques stand out: mechanomyography (MMG) and surface electromyography (EMG). They are used in medical research, ergonomics and sports training alike. However, they rely on different principles and each has its own advantages and limitations.

1. Measurement principles

EMG measures the electrical activity of muscles using electrodes placed on the skin. These electrodes record the electrical signals generated by muscle fibres as they contract. It is the reference system for measuring muscle activity, the “gold standard”.

MMG measures the mechanical vibrations produced by the muscle during contraction. It uses highly precise accelerometers to detect these tiny movements. Discovered in the 16th century but only studied in depth since the 1990s, MMG is now emerging as a genuine alternative to EMG that is easier to use in the field.

2. Main applications

EMG has traditionally been used in the laboratory: clinical medicine, sports research and fields where localised measurement of muscle activity is crucial.

MMG is particularly well suited to the field. It can be used, for example, to measure muscular effort and fatigue at work or during sports training, as we do at MOTEN.

3. Ease of use

EMG requires skin preparation: the skin must be shaved and disinfected before the electrodes are applied, which can be uncomfortable for subjects. Electrode placement must also be very precise, which makes it complex to use.

MMG requires no skin preparation. The sensors are simply placed over the muscle to be measured, making it more comfortable and easier to use.

4. Localisation of muscle activity

EMG is more precise for localising muscle activity, as it measures electrical signals at specific points. This requires some expertise: placing the electrodes a few centimetres away from the recommended point leads to signal loss.

MMG provides a more global view of muscle activity, which is sufficient for many applications. Distinguishing between two neighbouring muscles may be limited, but the results follow the same trends as those obtained with heavier tools.

5. Reliability and stability

EMG is sensitive to electrical interference, sweat and movement. Because it requires very precise electrode placement, an error of a few centimetres can distort the measurement. As sweat alters the electrical signal, EMG is poorly suited to long measurements.

MMG, which measures vibrations, is mainly sensitive to movement. Appropriate data processing isolates muscle activity. Sensor placement requires much less precision, which reduces the risk of distorting the measurement. Measurement duration depends only on battery life: more than ten hours with MOTEN.

On the reliability and sensitivity of the two techniques, a comparative study shows that MMG is as sensitive and reliable as EMG.

Summary table

Conclusion

MMG and EMG are two distinct techniques for measuring muscle activity. The choice depends on the needs of your application. In research, using them together can be useful, as they provide complementary information. In the field, in real-life situations, MMG is easier to use while providing precise and reliable data.