| Phonomyography | |
|---|---|
| Synonyms | Sound myography |
| Purpose | measure force of muscle contraction |
Phonomyography (PMG) (also known asacoustic myography,sound myography,vibromyography, andsurface mechanomyogram)[1][2] is a technique to measure the force ofmuscle contraction by recording the low frequency sounds created during muscular activity.
Although, until recently, less precise than the more traditionalmechanomyography, it is considerably easier to set up. The signal is measured usingcondenser microphone elements, piezoelectric sensors,accelerometers, or a combination of sensors attached to the skin.Hydrophones have also been used to measure muscles immersed in water. Improvements in microphones and contact transducers (piezoelectric devices), as well as recording systems, has meant that they have become available in a size and of a quality that enables them to be applied to a normal daily setting outside the clinic and the laboratory setting. These new possibilities provide a clinical tool for the assessment of patients with musculoskeletal complaints during daily activities, or assessment of athletes in terms of efficiency in use of muscles.[citation needed]
The sound created by muscle movement can be heard with the ear pressed up to a contracting muscle, but most of the energy is low frequency, below 20 Hz, making it inaudibleinfrasound.
Electromyography signals are typicallybandpass filtered from 10Hz to 500 Hz, by comparison. PMG signals are limited to 5 Hz to 100 Hz in some experiments.[1] Orizio states that the low-frequency response of the sensor is the most important feature, and should go as low as 1 Hz.[3]
Images of PMG waves are available in this creative commons-licensed document, "Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review".[3]
Muscle sounds were first described in print by the Jesuit scientistFrancesco Maria Grimaldi[4] in a posthumous publication of 1665, which influenced the work of the English physicianWilliam Hyde Wollaston[5] and the German scientistPaul Erman.[6] The latter enlisted the aid ofRené Laennec. Mechanical amplification was first employed byHermann von Helmholtz. The past two centuries of repeated rediscovery and neglect of the phenomenon were summarised by Stokes and Blythe[7] in 2001.
{{cite web}}: CS1 maint: archived copy as title (link)It is important to underline here that the term "surface mechanomyogram" was suggested during a CIBA Foundation Symposium in 1995 to overcome the terminological confusion caused by the habit of identifying the phenomenon with the electrical signal produced by different transducers (microphones, accelerometers,piezoelectric transducers, LVDs, etc.) instead of with its mechanical origin
