title: Trapezius muscle activity in using ordinary and ergonomically designed dentistry chairs.
abstract: BACKGROUND
  Most dentists complain of musculoskeletal disorders which can be caused by prolonged static posture, lack of suitable rest and other physical and psychological problems.
  
  
  OBJECTIVE
  We evaluated a chair with a new ergonomic design which incorporated forward leaning chest and arm supports.
  
  
  METHODS
  The chair was evaluated in the laboratory during task simulation and EMG analysis on 12 students and subjectively assessed by 30 professional dentists using an 18-item questionnaire. EMG activity of right and left trapezius muscles for 12 male students with no musculoskeletal disorders was measured while simulating common tasks like working on the teeth of the lower jaw.
  
  
  RESULTS
  Normalized EMG data showed significant reduction (p<0.05) in all EMG recordings of the trapezius muscle. Dentists also unanimously preferred the ergonomically designed chair.
  
  
  CONCLUSIONS
  Such ergonomically designed chairs should be introduced as early as possible in student training before bad postural habits are acquired.
authors.affiliation: Department of Industrial Engineering, Sharif University of Technology, Tehran, Iran. omidhad@gmail.com
authors.forename: O
authors.initials: O
authors.lastname: Haddad
authors.forename: M A
authors.initials: MA
authors.lastname: Sanjari
authors.forename: A
authors.initials: A
authors.lastname: Amirfazli
authors.forename: R
authors.initials: R
authors.lastname: Narimani
authors.forename: M
authors.initials: M
authors.lastname: Parnianpour
mesh_terms: D000328:Adult; D001291:Attitude of Health Personnel; D001415:Back; D001696:Biomechanical Phenomena; D003813:Dentistry; D004576:Electromyography; D006804:Ergonomics; D006801:Humans; D007374:Interior Design and Furnishings; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009140:Musculoskeletal Diseases / Q000517:prevention & control; D011187:Posture; D012782:Shoulder; D011795:Surveys and Questionnaires; D055815:Young Adult