Mechanomyography (MMG) :: essays research papers

MMG simply stated, is the sound that resonates from the muscle during a stimulated contraction. The act of pulling on a taught string and letting go has been related to model the sound generated by the muscle. This sound can be caused by the cycling of the actin myosin cross bridges, or perhaps by the gross lateral shift of the muscle, or maybe even the brief shock generated by the thickening of several active muscle fibers. These are three of the hypothesis that try to account for the sound emitted from the muscle. The exact cause of mechanomyography is yet to be determined, but there are a few attributes that can be spoken for. It is understood that ‘the muscle sound is related to muscle activity and its properties are related to the properties of the contraction.’ (8) The main frequency of MMG is 25 Hertz, British physicist, chemist, and physician William Wollaston determined this. This can possibly be attributed to the ATP turnover rate. ATP can hydrolyze and refurb ished at a rate of about 40msec, which translates into 25Hertz. (8,10)   Ã‚  Ã‚  Ã‚  Ã‚  The MMG signal can be recorded using a variety of transducers. One is the piezoelectric crystal contact sensor (microphone). Some researchers have used a hydrophone in studies when the muscle was submerged in water in vivo, others have used condensers.(11) It will be discussed later some of the differences between the types.   Ã‚  Ã‚  Ã‚  Ã‚  Factors that influence the MMG signal can include stiffness of the muscle, fluid in an around the muscle, temperature of the tissue, fiber type, gender, technique and equipment used, type of contraction performed, amount of fatigue, and cross talk between muscles.   Ã‚  Ã‚  Ã‚  Ã‚  Stiffness can alter the MMG by lowering the amplitude. As the muscle produces a greater force the stiffness of the muscle increases linearly with the force increase. When subject reaches 80 – 100% of MVC this stiffness can cause the amplitude of the signal to decrease due to the fusion of motor unit twitches, which will limit the oscillation.(2) This stiffness can also be attributed when talking about the different types of contraction.   Ã‚  Ã‚  Ã‚  Ã‚  Types of contraction have been shown to provoke different amounts of peak torque. Eccentric forms of contraction elicit greater force production than that of concentric. This could cause a greater stiffness in the muscle during eccentric contractions, which could lower the MMG. Also there is the mechanism behind the contraction that could be the factor.