Mean Frequency and Noise from Patients with Pathologies in Lower Limbs

Raw electromyography (EMG) signals are useful for several purposes in the analysis of muscles in both clinical and engineering applications. For instance, muscles fatigue is, typically, assessed by the mean frequency (MNF) of the EMG signal. Previous research works have shown that there is a positive correlation between the signal to noise ratio (SNR) of the EMG signal and its MNF value. The aim of this work is to determine and compare MNF in subjects with impairments in the lower limbs. Measurements of the MNF and the SNR were performed in nine muscles of six pathologic subjects, which were compared with a similar database of subjects without apparent pathologies. The MNF value was estimated using the power spectral density. The SNR for pathologic patients database was higher (17.28 +/- 1.67 dB) with respect to the database of subjects without apparent pathologies (12.86 +/- 1.71 dB). Subjects with pathologies in the lower limbs presented a decrease in the average value of the MNF.