title: Task-related variations in the surface EMG of the human first dorsal interosseous muscle.
abstract: Evidence from human and animal studies suggests that motor neuron pool organization is not uniform for all motor tasks. Groupings of motor units within a muscle may be recruited differentially for a given task based on principles beyond anatomical or architectural features of the muscle alone. This study aimed to determine whether: (1) there was differential activation across locations of the first dorsal interosseous (FDI) muscle during a given task, (2) the differential activation was related to directional requirements and/or end goal of the task, and (3) there was an anatomical pattern to the differential activation. Twenty-six healthy right-handed participants carried out isometric finger/hand contractions in sitting while surface EMG was collected from 4 bipolar sites on the FDI muscle simultaneously. The tasks included: abduction, flexion, diagonal, 30% abduction + 30% flexion, 30% flexion + 30% abduction, key pinch, and power grasp. Mean peak integrated EMG for each task was normalized to site and task specific mean M waves. Differential activation was evident across FDI sites based on movement direction, order of directional components within a combination condition, and end goal of the task. There was greatest activation in the distal ulnar site for all tasks. Additionally there was a trend toward an ordering effect in the amount of activation at each site: distal ulnar > distal radial > proximal radial > proximal ulnar.
authors.affiliation: National Rehabilitation Hospital, Neuroscience Research Center, 102 Irving Street NW, Washington, DC, 20010, USA. whitf026@umn.edu
authors.forename: Maureen
authors.initials: M
authors.lastname: Whitford
authors.forename: Carl G
authors.initials: CG
authors.lastname: Kukulka
mesh_terms: D000293:Adolescent; D000328:Adult; D004576:Electromyography / Q000379:methods*; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult