The electromyographic fatigue threshold is not a valid tool to assess muscle function.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Sports Science

Background:

• Muscle fatigue assessment is crucial for understanding neuromuscular function.
• Electromyography (EMG) is commonly used to evaluate muscle activity.
• The electromyographic fatigue threshold (EMG(FT)) aims to quantify fatigue onset.

Purpose of the Study:

• To determine the electromyographic fatigue threshold (EMG(FT)) using EMG activity level and frequency content.
• To assess the validity and reproducibility of EMG(FT) in the First Dorsal Interosseous muscle.

Main Methods:

• Thirty-seven healthy subjects performed isometric index abductions at varying percentages of maximal voluntary contraction (MVC).
• Surface EMG was recorded from the First Dorsal Interosseous using a linear electrode array.
• EMG(FT) was calculated from Root Mean Square (RMS) and Mean Power Frequency (MPF) if specific statistical criteria were met.

Main Results:

• EMG(FT) could not be determined in all subjects using either RMS (9/37) or MPF (27/37).
• Reproducibility of EMG(FT) determination from MPF was weak in subjects tested twice (ICC=-0.029).
• High variability and low success rates indicate challenges in establishing EMG(FT).

Conclusions:

• The EMG(FT) is not a valid or reproducible tool for assessing muscle function.
• Current methods for determining EMG(FT) require refinement for clinical or research application.
• Further research is needed to explore alternative or improved methods for fatigue assessment.