Upper Extremity Dynamics During Keying

Details

• Personal Author:
  Dennerlein J
• Description:
  Individuals spending a considerable amount of time working at a computer suffer high rates of upper extremity musculoskeletal disorders (MSDs). Recognizing that deleterious limb positions contribute to the development of MSDs, practitioners empirically recommend changes in workstation arrangements and keyboard design with the goal of reducing static postural loads. Research into these interventions has been limited and often neglects the dynamic task requirements and the interplay with observed static loading of the tissues. The proposed goal of this research was to determine which ergonomic interventions for computer workers reduce both the static and dynamic biomechanical load of the upper extremity, a critical step for testing their effectiveness. Through a series of musculoskeletal modeling and laboratory experimental procedures we improved current models of passive muscle characteristics of both the intrinsic and extrinsic muscles that articulate the hand. We then applied these models to dynamic tapping and demonstrated that negative tilt keyboards increase the load on the forearm muscles, an unexpected result that is contrary to most practice guidelines. Through inverse dynamic models of the hand, forearm, upper arm we calculated the dynamic torques, testing hypotheses that workstation and individual based interventions change these dynamic torques. Shoulder torques decrease with the use of forearm and palm supports; however, the effects are different for mousing compared to keyboarding. For keyboarding, palm supports also decrease shoulder torques; however, for mousing, palm supports did not reduce shoulder torques significantly. Finally, we found that typing style greatly effects upper extremity torque, specifically two-finger typists (hunt and peck) have large dynamic loading and increased variability in joint torques compared to touch typist who use all eight fingers. In addition to testing these specific hypotheses this work also expanded our capabilities in testing design aspects of mobile computing including developing specific measurement capabilities of the thumb during key activation typical of hand held computers. We successfully completed all aims of the study. [Description provided by NIOSH]
• Subjects:
  Biomechanical Phenomena Computers Ergonomics Musculoskeletal Diseases Musculoskeletal System Occupational Health Safety
• Keywords:
  Biomechanical Modeling Biomechanics Computer Equipment MSD Musculoskeletal Disorders Posture Upper Extremities
• Series:
  Grant Final Reports
• Publisher:
  National Institute for Occupational Safety and Health
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Final Grant Report
• Place as Subject:
  Massachusetts ; OSHA Region 1
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  OEP - Office of Extramural Programs
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  1-14
• NIOSHTIC Number:
  nn:20060525
• NTIS Accession Number:
  PB2021-100199
• Citation:
  Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, R01-OH-008373, 2012 Sep; :1-14
• Contact Point Address:
  PI: Jack Dennerlein, Ph.D., Department of Environmental Health, Harvard School of Public Health, Landmark Center, 404L, 401 Park Drive, Boston, MA 02215 USA
• Email:
  jax@hsph.harvard.edu
• Federal Fiscal Year:
  2012
• NORA Priority Area:
  Healthcare and Social Assistance ; Services ; Wholesale and Retail Trade
• Performing Organization:
  Harvard University School of Public Health
• Peer Reviewed:
  False
• Start Date:
  20070301
• Source Full Name:
  National Institute for Occupational Safety and Health
• End Date:
  20120228
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:6baa601c290564c6566fd1a36ce1cfc935ba7c196abe5ffe2893231a285933188eff0d570ee9b6764e8b1bf31665f8f1d692ef445c6db37ffa09613f75ef926c
• Download URL:
  https://stacks.cdc.gov/view/cdc/219002/cdc_219002_DS1.pdf
• File Type:
  [PDF - 902.37 KB ]