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Arm EMG during abduction and adduction: hysteresis cycle
J C Politti1, C J Felice, M E Valentinuzzi
1Departamento de Biongeniería (DBI), Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), 327 Correo Central, 4000, Tucumán, Argentina. jpolitti@herrera.unt.edu.ar
Electromyography (EMG) of the deltoid muscle reveals a hysteresis cycle during arm movements, indicating different muscle activation patterns for abduction versus adduction. This reproducible finding highlights distinct muscle recruitment for arm lifting and lowering.
Area of Science:
- Biomechanics
- Neuroscience
- Human Movement Science
Background:
- Electromyography (EMG) is crucial for quantifying shoulder joint behavior.
- Shoulder movements involve complex muscle coordination.
- The deltoid muscle plays a key role in shoulder abduction and adduction.
Purpose of the Study:
- To investigate the electromyographic (EMG) activity of the deltoid muscle during static shoulder abduction and adduction.
- To determine if EMG patterns differ between the lifting and lowering phases of arm movement.
- To identify potential differences in muscle activation contributing to shoulder joint dynamics.
Main Methods:
- Electromyographic (EMG) data were collected from the deltoid medium muscle in 16 subjects.
- Subjects performed static, sequential abduction-adduction movements of the arm.
- EMG amplitude was plotted against lateral angular position, and statistical analysis (paired Student t-test) was performed.
Main Results:
- A hysteresis cycle was observed in the deltoid medium EMG amplitude during abduction-adduction.
- A highly significant difference (p<0.001) was found in mean EMG values between abduction and adduction at the same angle.
- This effect was reproducible across all subjects within 0-90 degrees in the scapular plane.
Conclusions:
- Quantifiable and significant differences exist in deltoid medium EMG activity when preparing for abduction versus adduction.
- These differences suggest the involvement of different collaborating muscles (e.g., anterior/posterior deltoids) in arm lifting versus lowering.
- The findings provide insights into the neuromuscular control of complex shoulder movements.
