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

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

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. Vibration may be deterministic if the oscillations can be characterised precisely (e.g. the periodic motion of a pendulum), or random if the os ...

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 pendulum ...

s of the muscle

fibre Fiber (spelled fibre in British English; from ) 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 incorp ...

s at the

resonance frequency Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

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 device that measures the proper acceleration of an object. Proper acceleration is the acceleration (the rate of change (mathematics), rate of change of velocity) of the object relative to an observer who is in free fall (tha ...

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 publi ...

placed on the skin over the belly of the muscle. When measured using a microphone, it 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 electromyo ...

(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 noise power, often expressed in deci ...

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 (: prostheses; from ), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through physical trauma, disease, or a condition present at birth (Congenital, congenital disord ...

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 (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 164 ...

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 i ...

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. His work was mainly concerned with electricity and magnetism, though he also made some contributions ...

. 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; "von" since 1883) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The ...

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

References

{{reflist Medical tests