Bicoherence analysis of quadriceps electromyogram during isometric knee extension

Area of Science:

• Biomedical Engineering
• Neuroscience
• Sports Science

Background:

• Electromyogram (EMG) signals reflect muscle electrical activity.
• Bicoherence analysis is a technique to detect nonlinear interactions and phase coupling in time series data.
• Previous bicoherence analysis of EMG data is limited in the literature.

Purpose of the Study:

• To investigate the application of bicoherence analysis to vastus lateralis EMG during isometric knee extension.
• To identify nonlinear dynamics and phase coupling within EMG signals.
• To explore the potential of bicoherence analysis in sports rehabilitation and medicine.

Main Methods:

• Bicoherence analysis was performed on EMG data from 18 adult males performing isometric knee extension.
• Analysis focused on the vastus lateralis muscle.
• Validation tests included analysis of white noise data.

Main Results:

• Bicoherence spectra exhibited ridge-like features indicative of deterministic chaotic behavior, similar to EEG and ECG.
• No pronounced second-order phase coupling was found between specific EMG frequency bands.
• Subtle fluctuations in frequency histograms were attributed to the natural evolution of chaotic processes.

Conclusions:

• Bicoherence analysis of vastus lateralis EMG during isometric contraction suggests underlying chaotic dynamics but limited specific phase coupling.
• The findings do not preclude the utility of bicoherence analysis as a complementary technique for EMG frequency analysis.
• Further investigation is warranted to determine the full potential of EMG bicoherence in sports medicine and rehabilitation.