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
  More +
• Keywords:
  • Computer equipment
  • Keyboards
  • Musculoskeletal system disorders
  • MSD
  • Force
  • Posture
  • Statistical analysis
  • Muscles
  • Musculoskeletal system
  • Extremities
  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
• Download URL:
  https://stacks.cdc.gov/view/cdc/216956/cdc_216956_DS1.pdf
• File Type:
  [PDF - 245.46 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:433237247b567af864c1cd7d630fb3100d3836a8e4eb7e2b1211f988a3c03d9737f58546bb5901235f2f85ce12ca8ed0ecca865c9b1b9768ff09d68543c2ee33