Variability in Normalization Methods of Surface Electromyography Signals in Eccentric Hamstring Contraction

Area of Science:

• Biomechanics
• Human Movement Analysis
• Sports Science

Background:

• Surface electromyography (sEMG) signal normalization is critical in human movement analysis.
• Parameter selection for sEMG normalization requires rigorous justification.
• Understanding sEMG variability in hamstring contractions is essential for accurate performance assessment.

Purpose of the Study:

• To determine the variability of sEMG signals during eccentric hamstring contractions.
• To compare different normalization parameters for sEMG analysis in hamstring exercises.
• To identify the most reliable normalization method for eccentric hamstring contractions.

Main Methods:

• Cross-sectional study design.
• Involved nine university rugby players with no history of hamstring injury.
• sEMG signals were normalized using maximum voluntary isometric contraction and task-related values (Nordic hamstring exercise).
• Intersubject and intrasubject variation coefficients were calculated to assess normalization method variability and signal reproducibility.

Main Results:

• Intrasubject variation coefficients indicated acceptable sEMG reproducibility (below 12%) across all normalization methods.
• Normalization procedures utilizing task-related values yielded lower intersubject variation coefficients.
• Task-related parameters demonstrated reduced variability in sEMG amplitude normalization.

Conclusions:

• Parameters derived from task execution, such as the Nordic hamstring exercise, offer reduced variability for sEMG amplitude normalization.
• This finding is particularly relevant for analyzing eccentric hamstring muscle contractions.
• The study highlights the importance of selecting appropriate normalization parameters for reliable sEMG analysis in sports and movement science.