Keyswitch Orientation Can Reduce Finger Joint Torques During Tapping on a Computer Keyswitch

Details

• Personal Author:
  Balakrishnan AD ; Dennerlein, Jack T. ; Jindrich DL
• Description:
  Objective: To examine the effects of keyswitch orientation on joint torques. Background: The fingertip produces primarily vertical forces during single-finger tapping on a computer keyswitch. However, horizontal force components within the sagittal plane of the finger could reduce net joint torques. Method: Eleven participants tapped on a keyswitch oriented in three directions: vertical, tilted 30 degrees such that when pressed it moved away from the user (similar to a positive-tilt keyboard), and tilted 30 degrees such that when pressed it moved toward the user (similar to a negative-tilt keyboard). Participants also tapped on a prototype cantilever keyswitch design in which the key cap moves along the arc of a bending beam gradually away from the user. Miniature electro-optical goniometers measured the finger posture, and a two-axis force sensor measured fingertip forces. Results: Tapping on a keyswitch oriented such that it moves away from the user when pressed reduced net joint torques by 47% relative to tapping on a vertically orientated keyswitch and by 56% relative to tapping on a keyswitch oriented toward the user, whereas the cantilever design resulted in 14% decreases in net joint torque relative to the vertical orientation. Conclusion: Reductions of torques resulted from decreasing the moment arm of the fingertip force about the joints. Application: Keyboard design should incorporate keyswitch mechanism angles along with other postural and geometric constraints to reduce exposure of the finger joints and muscles to force during typing. [Description provided by NIOSH]
• Subjects:
  Computers Environmental Exposure Fatigue Men Musculoskeletal Diseases Musculoskeletal System Occupational Health Risk Assessment Risk Factors Safety Women

  More +
• Keywords:
  Computer Equipment Exposure Levels Extremities Force Humans Keyboards MSD Muscles Musculoskeletal System Musculoskeletal System Disorders Posture Risk Factors Statistical Analysis

  More +
• ISSN:
  0018-7208
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Massachusetts ; OSHA Region 1
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  121-129
• Volume:
  48
• Issue:
  1
• NIOSHTIC Number:
  nn:20054371
• Citation:
  Hum Factors 2006 Mar; 48(1):121-129
• Contact Point Address:
  Jack T. Dennerlein, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115
• Email:
  jax@hsph.harvard.edu
• Federal Fiscal Year:
  2006
• Performing Organization:
  Harvard School of Public Health
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Human Factors
• End Date:
  20280630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:433237247b567af864c1cd7d630fb3100d3836a8e4eb7e2b1211f988a3c03d9737f58546bb5901235f2f85ce12ca8ed0ecca865c9b1b9768ff09d68543c2ee33
• Download URL:
  https://stacks.cdc.gov/view/cdc/216956/cdc_216956_DS1.pdf
• File Type:
  [PDF - 245.46 KB ]