Test-retest reliability of trunk motor variability measured by large-array surface electromyography.

Area of Science:

• Biomechanics
• Neuroscience
• Human Movement Science

Background:

• Understanding trunk muscle activity patterns is crucial for diagnosing and managing neuromusculoskeletal conditions.
• Muscle fatigue significantly alters motor control strategies, impacting muscle activation distribution.
• Large-array surface electromyography (EMG) offers a detailed, non-invasive method to assess muscle activation patterns.

Purpose of the Study:

• To assess the test-retest reliability of trunk muscle activity distribution during induced muscle fatigue.
• To investigate how muscle fatigue affects the reliability of motor variability measures in asymptomatic individuals.
• To determine the consistency of trunk muscle activation patterns over time using large-array surface EMG.

Main Methods:

• Twenty-seven asymptomatic volunteers underwent two sessions of large-array surface EMG recordings.
• Trunk muscle activity distribution was assessed during a low back muscle fatigue task.
• Motor variability was quantified using centroid coordinates and a dispersion variable, with reliability analyzed via Pearson correlation coefficients.

Main Results:

• Muscle fatigue induced a shift in EMG amplitude distribution towards the lateral-caudal region of the lumbar erector spinae.
• High test-retest reliability (moderate to very strong correlations) was observed in later fatigue stages for both motor variability measures.
• Lower reliability (weak to moderate correlations) was found in the initial fatigue phases, particularly for the dispersion variable.

Conclusions:

• Trunk muscle activity patterns exhibit reduced reliability during the early phases of muscle fatigue in asymptomatic individuals.
• Later stages of muscle fatigue are characterized by more consistent and reliable patterns of EMG activity.
• These findings highlight the dynamic nature of muscle activation reliability under fatiguing conditions.