Surface EMG recorded by branched electrodes during sustained muscle activity

Area of Science:

• Biomedical Engineering
• Neuroscience
• Sports Science

Background:

• Muscle fatigue assessment is crucial for understanding performance limitations and injury prevention.
• Surface electromyography (sEMG) offers a non-invasive method for evaluating muscle activity.
• Traditional sEMG analysis methods may not fully capture the nuances of muscle fatigue during sustained contractions.

Purpose of the Study:

• To investigate the utility of surface interference EMG with level-trigger averaging for assessing muscle fatigue.
• To determine the most appropriate sEMG parameter for quantifying muscle fatigue during isometric contractions at various intensity levels.

Main Methods:

• Surface interference EMG was recorded using branched electrodes during sustained voluntary isometric contractions.
• Level-trigger averaging and turn/amplitude analysis were applied to the EMG signals.
• Conduction velocity (CV) was calculated from the time shift of averaged potentials (AvPs) between two electrodes.

Main Results:

• Conduction velocity (CV) consistently declined across all sustained contraction levels, indicating muscle fatigue.
• Changes in negative amplitude (NA), turns per second, and mean amplitude of turns varied with contraction intensity.
• CV decrease showed a strong correlation with torque reduction during maximal efforts.

Conclusions:

• Surface EMG with level-trigger averaging is a convenient and non-invasive technique for routine muscle fatigue assessment.
• Conduction velocity (CV) is the most reliable parameter for quantifying muscle fatigue during isometric contractions.
• This method provides valuable insights into neuromuscular responses during sustained muscle effort.