Extracting extensor digitorum communis activation patterns using high-density surface electromyography

Area of Science:

• Biomechanics
• Neuroscience
• Human Motor Control

Background:

• The extensor digitorum communis (EDC) muscle is crucial for hand dexterity and object manipulation.
• It's hypothesized that separate motoneuron pools control distinct EDC compartments for individual digits.
• Previous studies lacked detailed tracking of EDC spatial activation patterns during individual finger extensions under varied conditions.

Purpose of the Study:

• To quantify the global spatial activation patterns of the EDC muscle.
• To investigate these patterns during individual finger extensions using high-density surface electromyography (EMG).
• To analyze activation patterns across different effort levels and finger constraint conditions.

Main Methods:

• Utilized a high-density (7 × 9) surface EMG grid to record muscle activity.
• Constructed muscle activation maps based on root mean square (RMS) of EMG signals.
• Subjects performed individual finger extensions (index, middle, ring, little) at the metacarpophalangeal joint under static and dynamic constraints and varying effort levels.

Main Results:

• Distinct spatial activation patterns were observed for individual finger extensions, particularly between the index and middle fingers.
• Strong covariance in activation was noted between the ring and little finger extensions.
• Activation patterns remained consistent across different contraction levels and finger constraint conditions.
• Distinctions in activation were more pronounced in the proximal-distal direction compared to the radial-ulnar direction.

Conclusions:

• Global spatial activation mapping of the EDC muscle using surface EMG can localize individual compartments during finger extensions.
• This technique offers potential for developing more selective control inputs for assistive devices.
• Findings provide a foundation for understanding hand impairments in individuals with neurological disorders.