title: Associations between cervical and scapular posture and the spatial distribution of trapezius muscle activity.
abstract: The first aim of this investigation was to quantify the distribution of trapezius muscle activity with different scapular postures while seated. The second aim of this investigation was to examine the association between changes in cervical and scapular posture when attempting to recruit different subdivisions of the trapezius muscle. Cervical posture, scapular posture, and trapezius muscle activity were recorded from 20 healthy participants during three directed shoulder postures. Planar angles formed by reflective markers placed on the acromion process, C7, and tragus were used to quantify cervical and scapular posture. Distribution of trapezius muscle activity was recorded using two high-density surface electromyography (HDsEMG) electrodes positioned over the upper, middle, and lower trapezius. Results validated the assumption that directed scapular postures preferentially activate different subdivisions of the trapezius muscle. In particular, scapular depression was associated with a more inferior location of trapezius muscle activity (r=0.53). Scapular elevation was coupled with scapular abduction (r=0.52). Scapular adduction was coupled with cervical extension (r=0.35); all other changes in cervical posture were independent of changes in scapular posture. This investigation provides empirical support for reductions in static loading of the upper trapezius and improvements in neck posture through verbal cueing of scapular posture.
authors.affiliation: Department of Mechanical and Materials Engineering, University of Denver, United States.
authors.forename: Brecca M
authors.initials: BM
authors.lastname: Gaffney
authors.affiliation: Department of Physical Medicine and Rehabilitation, Physical Therapy and Rehabilitation Science Programs, University of Colorado Anschutz Medical Campus, United States.
authors.forename: Katrina S
authors.initials: KS
authors.lastname: Maluf
authors.affiliation: Division of Biostatistics and Bioinformatics, National Jewish Health, United States; Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, United States.
authors.forename: Douglas
authors.initials: D
authors.lastname: Curran-Everett
authors.affiliation: Department of Mechanical and Materials Engineering, University of Denver, United States. Electronic address: bradley.davidson@du.edu.
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Davidson
mesh_terms: D000328:Adult; D001415:Back / Q000502:physiology*; D004566:Electrodes; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*; D012540:Scapula / Q000502:physiology*; D012782:Shoulder; D012785:Shoulder Joint / Q000502:physiology; D064171:Superficial Back Muscles / Q000502:physiology*; D055815:Young Adult
keywords: Cervical posture; High-density EMG; Scapular posture; Trapezius muscle