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

Hu X, Suresh NL, Xue C, Rymer WZ - Front Physiol (2015)

Bottom Line: Our results revealed distinct activation patterns during individual finger extensions, especially between index and middle finger extensions, although the activation between ring and little finger extensions showed strong covariance.We also found that distinct activation patterns were more discernible in the proximal-distal direction than in the radial-ulnar direction.Such information can also provide a basis for understanding hand impairment in individuals with neural disorders.

View Article: PubMed Central - PubMed

Affiliation: Sensory Motor Performance Program, Single Motor Unit Lab, Rehabilitation Institute of Chicago Chicago, IL, USA.

ABSTRACT
The extensor digitorum communis muscle plays an important role in hand dexterity during object manipulations. This multi-tendinous muscle is believed to be controlled through separate motoneuron pools, thereby forming different compartments that control individual digits. However, due to the complex anatomical variations across individuals and the flexibility of neural control strategies, the spatial activation patterns of the extensor digitorum communis compartments during individual finger extension have not been fully tracked under different task conditions. The objective of this study was to quantify the global spatial activation patterns of the extensor digitorum communis using high-density (7 × 9) surface electromyogram (EMG) recordings. The muscle activation map (based on the root mean square of the EMG) was constructed when subjects performed individual four finger extensions at the metacarpophalangeal joint, at different effort levels and under different finger constraints (static and dynamic). Our results revealed distinct activation patterns during individual finger extensions, especially between index and middle finger extensions, although the activation between ring and little finger extensions showed strong covariance. The activation map was relatively consistent at different muscle contraction levels and for different finger constraint conditions. We also found that distinct activation patterns were more discernible in the proximal-distal direction than in the radial-ulnar direction. The global spatial activation map utilizing surface grid EMG of the extensor digitorum communis muscle provides information for localizing individual compartments of the extensor muscle during finger extensions. This is of potential value for identifying more selective control input for assistive devices. Such information can also provide a basis for understanding hand impairment in individuals with neural disorders.

No MeSH data available.


Related in: MedlinePlus

Electrode placement and EMG signals. (A) A 7 × 9 EMG electrode grid was placed over the skin of the forearm based on the anatomical landmarks of the forearm, and the absolute inter-electrode distance was not uniform. (B) The grid organization is presented in the relative forearm length and circumference dimensions. (C) The segments (150 ms) of EMG signals recorded from all electrodes during a four-finger extension task are shown.
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Figure 1: Electrode placement and EMG signals. (A) A 7 × 9 EMG electrode grid was placed over the skin of the forearm based on the anatomical landmarks of the forearm, and the absolute inter-electrode distance was not uniform. (B) The grid organization is presented in the relative forearm length and circumference dimensions. (C) The segments (150 ms) of EMG signals recorded from all electrodes during a four-finger extension task are shown.

Mentions: Participants were seated upright in a chair with their forearm pronated 90° resting on a table and wrist in 0° (radial or ulnar) deviation. Their palm rested on an aluminum 120° arc plate, resulting the wrist in 30° extension and fingers in 60° flexion about the metacarpophalangeal joint and 0° flexion or extension about the interphalangeal joints. During the experiment, subjects were asked to extend their individual metacarpophalangeal joints either freely (dynamic condition) or while their fingers were constrained by a plastic board (static condition). In both dynamic and static conditions, the increment of muscle contraction level was self-paced at a comfortable rate for individual subjects. In dynamic conditions, subjects either performed a full extension (~60°) termed high effort, or they extended their joint (~30°) until their digits were horizontal in parallel with the table surface, termed low effort. In static conditions, they extended their fingers against the plastic board using high or low efforts, and visual feedback of the EMG signals from all the channels were provided to guide their effort level. The subjects also extended all their four fingers simultaneously as a control (dynamic or static and high or low efforts) for each condition. The effort level was quantified using the average RMS of EMG signals recorded across all the channels. At each condition, subjects were instructed to extend their fingers and maintain the steady effort for 5 s, and they repeated the task three times with a 4 s of relaxation period between contractions (Figure 1). Prior to the main testing session, subjects were given practice trials to become familiarized with the task to ensure that they can perform the individual finger extension at different effort levels. The different conditions were randomized within and between subjects.


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

Hu X, Suresh NL, Xue C, Rymer WZ - Front Physiol (2015)

Electrode placement and EMG signals. (A) A 7 × 9 EMG electrode grid was placed over the skin of the forearm based on the anatomical landmarks of the forearm, and the absolute inter-electrode distance was not uniform. (B) The grid organization is presented in the relative forearm length and circumference dimensions. (C) The segments (150 ms) of EMG signals recorded from all electrodes during a four-finger extension task are shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593961&req=5

Figure 1: Electrode placement and EMG signals. (A) A 7 × 9 EMG electrode grid was placed over the skin of the forearm based on the anatomical landmarks of the forearm, and the absolute inter-electrode distance was not uniform. (B) The grid organization is presented in the relative forearm length and circumference dimensions. (C) The segments (150 ms) of EMG signals recorded from all electrodes during a four-finger extension task are shown.
Mentions: Participants were seated upright in a chair with their forearm pronated 90° resting on a table and wrist in 0° (radial or ulnar) deviation. Their palm rested on an aluminum 120° arc plate, resulting the wrist in 30° extension and fingers in 60° flexion about the metacarpophalangeal joint and 0° flexion or extension about the interphalangeal joints. During the experiment, subjects were asked to extend their individual metacarpophalangeal joints either freely (dynamic condition) or while their fingers were constrained by a plastic board (static condition). In both dynamic and static conditions, the increment of muscle contraction level was self-paced at a comfortable rate for individual subjects. In dynamic conditions, subjects either performed a full extension (~60°) termed high effort, or they extended their joint (~30°) until their digits were horizontal in parallel with the table surface, termed low effort. In static conditions, they extended their fingers against the plastic board using high or low efforts, and visual feedback of the EMG signals from all the channels were provided to guide their effort level. The subjects also extended all their four fingers simultaneously as a control (dynamic or static and high or low efforts) for each condition. The effort level was quantified using the average RMS of EMG signals recorded across all the channels. At each condition, subjects were instructed to extend their fingers and maintain the steady effort for 5 s, and they repeated the task three times with a 4 s of relaxation period between contractions (Figure 1). Prior to the main testing session, subjects were given practice trials to become familiarized with the task to ensure that they can perform the individual finger extension at different effort levels. The different conditions were randomized within and between subjects.

Bottom Line: Our results revealed distinct activation patterns during individual finger extensions, especially between index and middle finger extensions, although the activation between ring and little finger extensions showed strong covariance.We also found that distinct activation patterns were more discernible in the proximal-distal direction than in the radial-ulnar direction.Such information can also provide a basis for understanding hand impairment in individuals with neural disorders.

View Article: PubMed Central - PubMed

Affiliation: Sensory Motor Performance Program, Single Motor Unit Lab, Rehabilitation Institute of Chicago Chicago, IL, USA.

ABSTRACT
The extensor digitorum communis muscle plays an important role in hand dexterity during object manipulations. This multi-tendinous muscle is believed to be controlled through separate motoneuron pools, thereby forming different compartments that control individual digits. However, due to the complex anatomical variations across individuals and the flexibility of neural control strategies, the spatial activation patterns of the extensor digitorum communis compartments during individual finger extension have not been fully tracked under different task conditions. The objective of this study was to quantify the global spatial activation patterns of the extensor digitorum communis using high-density (7 × 9) surface electromyogram (EMG) recordings. The muscle activation map (based on the root mean square of the EMG) was constructed when subjects performed individual four finger extensions at the metacarpophalangeal joint, at different effort levels and under different finger constraints (static and dynamic). Our results revealed distinct activation patterns during individual finger extensions, especially between index and middle finger extensions, although the activation between ring and little finger extensions showed strong covariance. The activation map was relatively consistent at different muscle contraction levels and for different finger constraint conditions. We also found that distinct activation patterns were more discernible in the proximal-distal direction than in the radial-ulnar direction. The global spatial activation map utilizing surface grid EMG of the extensor digitorum communis muscle provides information for localizing individual compartments of the extensor muscle during finger extensions. This is of potential value for identifying more selective control input for assistive devices. Such information can also provide a basis for understanding hand impairment in individuals with neural disorders.

No MeSH data available.


Related in: MedlinePlus