Comparison of an accelerometer and piezoelectric contact sensor for examining the mechanomyographic signal from the vastus medialis during isometric muscle actions

Background and objective: The purpose of this study was to compare an accelerometer (ACC) and a piezoelectric contact sensor (PEC) for the measurement of mechanomyographic (MMG) signals during submaximal to maximal isometric muscle actions of the vastus medialis.

Materials and methods: Following the determination of maximal isometric strength (MVC), eight subjects (20.4 ± 1.3 years) performed isometric muscle actions at 10 to 90% isometric MVC in random order. An ACC and PEC were used to simultaneously record the MMG signal.

Results: For the composite data, there were linear increases in normalized MMG amplitude for both the ACC(r ^{2} = 0.930) and PEC (r ^{2} = 0.875), with no difference in slope coefficients (p > 0.05). Similarly, there were linear increases in MMG mean power frequency (MPF) for the ACC (r ^{2} = 0.957) and PEC (r ^{2} = 0.982), with no difference in slope coefficients (p > 0.05). Analysis of individual subject data revealed there were no significant differences in slope coefficients between sensors for MMG amplitude or MPF for any subject with the exception of a significant difference (p < 0.05) for MMG MPF for one subject. In addition, there were no significant (p > 0.05) mean differences between the ACC and PEC for normalized MMG amplitude or MPF.

Conclusion: These results indicated that the ACC and PEC provide comparable information regarding MMG amplitude and MPF vs. isometric torque relationships of the vastus medialis.