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Reliability of Between-Session Motor Units Behavior: A Comparison of Analytical Approaches for Intervention Studies
Daniel Marcos-Frutos1, Kevin Méndez-Bouza2, David Colomer-Poveda3
1Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, 18071 Granada, Spain.
Objective:
To compare the between-session reliability of motor units (MUs) behavior derived from high-density surface electromyography (HD-sEMG) during isometric knee extension across three analytical approaches: all identified MUs averaged per participant, tracked MUs averaged per participant, and tracked MUs using individual MUs as the statistical unit.
Methods:
Seventeen resistance-trained volunteers completed one familiarization and two identical experimental sessions. HD-sEMG signals were assessed in vastus lateralis at 30%, 50%, and 70% of maximum voluntary torque (MVT). Plateau discharge rate, recruitment discharge rate, and recruitment threshold (expressed in %MVT and Nm) were calculated. Reliability was quantified with the Standard error of the measurement (SEM), Coefficient of variation (CV), and Intraclass correlation coefficient (ICC).
Results:
All identified MUs averaged per participant (CV = 11.7%, ICC = 0.73) yielded comparable reliability than tracked MUs averaged per participant (CV = 13.7%, ICC = 0.68). Using the individual MU as the statistical unit produced the lowest reliability (CV = 16.6%, ICC = 0.58).
Conclusions:
Averaging all identified MUs per participant achieved reliability comparable to tracking, without the associated sample loss or workload, supporting it as the preferable analytical approach for training interventions.
