Tracking motor units longitudinally across experimental sessions with high-density surface electromyography

Area of Science:

• Neuromuscular Physiology
• Biomedical Engineering
• Motor Control

Background:

• Traditional motor unit (MU) analysis methods limit tracking the same MUs across experimental sessions.
• This hinders understanding MU property adjustments due to training or neuromuscular disorders.

Purpose of the Study:

• To develop and validate a novel processing method for tracking individual MUs across multiple experimental sessions.
• To enable sensitive and reliable longitudinal monitoring of MU behavior and properties.

Main Methods:

• Utilized high-density surface electromyography (HD-sEMG) with a novel decomposition approach.
• Two experiments assessed reliability (tracking across 1-2 weeks) and sensitivity (detecting training-induced changes).
• Participants performed isometric knee extensions; Experiment II included 2 weeks of endurance training.

Main Results:

• Successfully tracked 38-40% of MUs across sessions separated by weeks.
• Tracked MUs demonstrated higher reliability (ICC 0.63-0.99) compared to all identified MUs (ICC 0.39-0.95).
• Detected significant training-induced changes in MU conduction velocity (effect size 2.1 for tracked MUs).

Conclusions:

• The proposed HD-sEMG method allows reliable tracking of individual MUs over extended periods.
• This facilitates sensitive monitoring of MU property changes related to interventions or disease progression.
• Opens new avenues for understanding neuromuscular adaptations and pathologies.