EMG power spectrum of elbow extensors: a reliability study

In order to be considered a potential tool for the characterization of muscle activity, the reliability of EMG power spectral analysis should be demonstrated. In this study, the reliability of the mean power frequency (MPF) and of the median frequency (MF) of power spectra (triceps brachii (TB), anconeus (AN)) obtained at different force levels from both ramp and stepwise isometric contractions was tested across three similar sessions performed on three different days (N = 9). Two-way ANOVAs for repeated measures did not disclose any significant differences (p > 0.05) in the value of either the MF or the MPF across the different sessions for either type of contraction. In contrast, significant changes (p < 0.05) in both the MF and the MPF were found across force levels. No significant interactions (p > 0.05) were found between the session and the force factors, for any of the analyses performed. The present results indicate that the MPF and the MF of the EMG power spectrum, taken at a specific force level, are reliable measures across sessions performed on different days. Consequently, this supports the possible use of power spectral analysis of EMG signals as an evaluation technique that could monitor changes in the neuromuscular system that can occur over a given period.