Iran Occupational Health

  Background and aims

  Recordings of electrical activity in the muscle and surface electromyography (EMG) have been widely used in the field of applied physiology. In parallel to  recording of the EMG, the detectable low-frequency vibration signal generated by the skeletal  muscle has been known and well documented. As the nature of the signal has been progressively   revealed, the term of mechanomyography (MMG) has been proposed by a recent review. The  main mechanism of the MMG generation has been considered to be sound pressure waves due to  the dimensional changes, i.e., lateral expansion of the activated muscle fibres.

  Methods

  Low-frequency vibrations produced by muscle fibres are clearly distinguishable from  the EMG, because MMG and EMG exhibit differences in response latency, spike duration, and  frequency. During voluntary contraction at constant force the MMG frequency content does not

  change significantly.

  Results

  This suggests that the frequency of MMG signal is directly related to the absolute force level of the muscle, irrespective of fatigue phenomena. At low force contractions, in contrast to   EMG signal, the changes in the amplitude content of the MMG are more consistent with muscle  fatigue. This indicated that the amplitude of MMG signal might be recommended as a method to  improve the objective and reliable detection of muscle fatigue induced by low force contraction.

  Conclusion

  MMG is most likely a valuable supplement to EMG as a non-invasive method to  examine various aspects of muscle function including fatigue, electromechanical delay, muscle fibre type patterns, age related changes in muscular performance, muscle atrophy, and neuromuscular performance.