The reliability of surface EMG derived motor unit variables

Area of Science:

• Neuromuscular Physiology
• Biomedical Engineering
• Motor Control

Background:

• Surface electromyography (sEMG) decomposition enables motor unit (MU) analysis for studying neural control.
• Longer-term reliability of MU variables is crucial for intervention studies but remains under-investigated.

Purpose of the Study:

• To assess the three-month reliability of MU variables in the flexor carpi radialis (FCR) and tibialis anterior (TA) muscles.
• To determine the stability and consistency of MU parameters over an extended period.

Main Methods:

• Forty participants performed isometric wrist flexion (FCR) or dorsiflexion (TA) across four sessions spanning 13 weeks.
• Surface EMG decomposition was used to record MU activity during maximal voluntary contractions (MVC) and ramp contractions.
• Intraclass correlation coefficients (ICC) were calculated to quantify the reliability of MU variables.

Main Results:

• Maximal force demonstrated high reliability (ICC = 0.94-0.99).
• Most MU variables in both FCR (ICC = 0.49-0.92) and TA (ICC = 0.58-0.96) showed good to excellent reliability.
• Common drive analysis indicated no significant differences between FCR and TA muscles across sessions.

Conclusions:

• MU variables derived from sEMG decomposition exhibit good longer-term reliability in FCR and TA muscles.
• These findings support the use of MU variables for monitoring neuromuscular adaptations in longitudinal intervention studies.
• The stability of MU variables suggests their validity for tracking changes in neural control over time.