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Uneven spatial distribution of surface EMG: what does it mean?
Alessio Gallina1, Roberto Merletti, Marco Gazzoni
1Laboratory for Engineering of the Neuromuscular System, LISiN, Politecnico di Torino, Torino, Italy. alessio.gallina@delen.polito.it
European Journal of Applied Physiology
|September 25, 2012
Summary
High-density surface electromyography (sEMG) reveals changes in muscle activity during force contractions. Spatial distribution of motor unit recruitment in the trapezius muscle varies with force levels and task repetition.
Area of Science:
- Biomechanics
- Neuroscience
- Human Physiology
Background:
- Surface electromyography (sEMG) is crucial for assessing muscle activity.
- Understanding muscle activation patterns during dynamic contractions is complex.
- High-density sEMG offers detailed spatial information about muscle recruitment.
Purpose of the Study:
- To investigate changes in sEMG amplitude distribution during repetitive, non-constant force contractions.
- To analyze how force level, subject, electrode position, and task repetition affect sEMG spatial patterns.
- To interpret these changes in the context of motor unit recruitment within the trapezius muscle.
Main Methods:
- Twelve healthy males performed isometric shoulder elevations with a force ramp up to 25% of maximal voluntary contraction (MVC).
- A 64-electrode matrix recorded sEMG from the trapezius muscle.
- sEMG amplitude distribution was analyzed across different force levels (5-25% MVC) and repetitions.
Main Results:
- sEMG amplitude was significantly lower over muscle tendons.
- The center of the sEMG amplitude distribution (barycenter) was subject-specific.
- The barycenter shifted caudally with increasing force and cranially with task repetition (p < 0.01).
Conclusions:
- High-density sEMG provides valuable insights into muscle activity patterns.
- Variations in spatial distribution of motor unit recruitment may explain upper trapezius activation variability.
- This technique aids in studying muscle function during force-varying isometric contractions.
