The mechanomyogram (MMG) is the mechanical signal observable from the surface of a

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

when the muscle is contracted. At the onset of muscle contraction, gross changes in the muscle shape cause a large peak in the MMG. Subsequent

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic, such as the motion of a pendulum—or random, su ...

s are due to

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendul ...

s of the muscle

fibre Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...

s at the

resonance frequency Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillat ...

of the muscle. The mechanomyogram is also known as the phonomyogram, acoustic myogram, sound myogram, vibromyogram or muscle sound.

Signal characteristics

The MMG is a low frequency vibration that may be observed when a muscle is contracted using suitable measuring techniques.

Measurement techniques

It can be measured using an

accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is acce ...

or a

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...

placed on the skin over the belly of the muscle. When measured using a microphone is may be termed the acoustic myogram.

Uses

The MMG may provide a useful alternative to the

electromyogram Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyog ...

(EMG) for monitoring muscle activity. It has a higher

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in de ...

than the surface EMG and thus can be used to monitor muscle activity from deeper muscles without using invasive measurement techniques. It is currently the subject of research activity into

prosthetic In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...

control and assistive technologies for the disabled.

History

Muscle sounds were first described in print by the Jesuit scientist

Francesco Maria Grimaldi Francesco Maria Grimaldi, SJ (2 April 1618 – 28 December 1663) was an Italian Jesuit priest, mathematician and physicist who taught at the Jesuit college in Bologna. He was born in Bologna to Paride Grimaldi and Anna Cattani. Work Between ...

in a posthumous publication of 1665, which influenced the work of the English physician

William Hyde Wollaston William Hyde Wollaston (; 6 August 1766 – 22 December 1828) was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingot ...

and the German physicist

Paul Erman Paul Erman (29 February 1764 – 11 October 1851) was a German physicist from Berlin, Brandenburg and a Huguenot of the fourth generation. He was the son of the historian Jean Pierre Erman (1735–1814), author of ''Histoire des réfugiés' ...

. The latter enlisted the aid of

René Laennec René-Théophile-Hyacinthe Laennec (; 17 February 1781 – 13 August 1826) was a French physician and musician. His skill at carving his own wooden flutes led him to invent the stethoscope in 1816, while working at the Hôpital Necker ...

. Mechanical amplification was first employed by

Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (31 August 1821 – 8 September 1894) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The Helmholtz Associat ...

. The past two centuries of repeated rediscovery and neglect of the phenomenon were summarised by Stokes and Blythe in 2001.

References

{{reflist Medical tests