EMG power spectra frequencies associated with various motor unit recruitment strategies

The objective of this study is to validate the hypothesis described, establishing the relationships between the MF (median frequency) and orderly recruitment of motor units. It is shown that linear orderly recruitment results in linear increase in the MF. It is also clear that firing-rate (FR) increase does not have an impact on the MF during recruitment or by itself. It is therefore concluded that the MF is directly related to orderly recruitment of motor units via their CV properties. It is also suggested that the MF monitoring during voluntary, increasing force contraction can identify the muscle recruitment strategy but not its FR behavior