Although the analysis in the frequency domain of the Electromyographic Signal (EMG) has been used in the characterization of the localized muscular fatigue process, its application, specifically the Median Frequency (MF), is rarely explored in sports. The objective of this study was to verify the viability of the EMG signal application, through its frequency domain analysis, as a parameter for determination and differentiation of the behavior of localized muscle fatigue. Two groups of subjects, one characterized as athletes (n = 12) and the other as sedentary (n = 12), were submitted to analysis based on procedures from three different experimental situations, all involving isometric exercise modality: i) maximum test for determination of the Maximum Voluntary Isometric Contraction (MVIC); ii) fatigue test, 35 sec. sustained load of 80% of MVIC; iii) recovery test, 10 sec. sustained load of 80% of MVIC. In the latter, the MF behavior in the three first (Fmedi) and three last (Fmedf) seconds of the EMG signal of tibialis anterior muscle during the fatigue test have been monitored. During the 10 seconds of the recovery test, MF was calculated regarding the whole period (Fmedr); this parameter was used to calculate the Muscular Recovery Index (MRI). The results showed that Fmedf presented lower value in relation to Fmedi in both groups (p < 0.05). Additionally, the Fmedi and Fmedf values for the athlete group were higher in comparison to the sedentary group (p < 0.05). The MRI mean value and standard deviation for the athlete group were 62.1% ± 28.7 and for the sedentary group was 55.2% ± 27.8 (p > 0.05). Therefore, the results presented in this study allow inferring the viability in the application of the frequency domain parameters of the EMG signal for the determination and differentiation of localized muscle fatigue behavior.
biomechanics; electromyography; muscle fatigue; tibialis anterior muscle; digital signal processing; sports
