Musculoskeletal disorder risk factors

• Repeated exertions
• Fingers & wrist due to keying
• Static exertions
• Trunk, neck & shoulders to:
• reach keyboard
• reach mouse
• see monitor
• hold phone
• Forceful exertions
• Excessive keying force
• Handling heavy documents
• Contact stresses
• Wrist & forearms from edge of keyboard and work surface
• Forearms and elbows from arm rests
• Stressful postures
• Neck flexion when monitor is too low
• Neck extension when using bi-focal corrective lens
• Neck deviation to hold phone
• Shoulder flexion to reach keyboard
• Forearm rotation to position hands over keyboard & mouse
• Wrist deviation when:
  • keying
  • using keys around perimeter of keyboard
  • mousing
• Wrist flexion and extension to position fingers over keys
• Prolonged work periods without breaks
• To meet deadlines
• To earn incentive pay

• What problems can you see and what problems can you anticipate in the jobs and work sites shown below?
• Based on your expert knowledge of ergonomics, how would you re-design the work station to prevent those possible "problems." Be specific!

a	b

Figure 1: Two workers share the same work stations, a and b. Worker 1 is 200cm tall and worker 2 is 151cm tall, c.

Small female (5%tile stature -- 151.1cm stature)

1c

Problem 2

Based on the following representative Figures, a and b, of a conventional keyboard explain where and when this operator might benefit from a so called "ergonomic" keyboard, c.

3a	3b
3c

Figure 3: Operator performing alphabetical, a, and numeric, b, data entry with conventional keyboard. Operator performing alpabetical data entry with "ergonomic" keyboard, c.

ANSI-HFS100 VDT Standard

• Chairs: �compressed seat height�
  • shall allow the user to place feet firmly on a support surface
  • shall be 40.6-52.0cm (16.0-20.5in)
  • use higher heights to control arm/wrist posture
  • use foot rest as needed
• Keyboard & display surface
  • shall permit a forearm angle with respect to the seatback between 70�+Y/2 and 90�+Y/2 where Y is the seat back angle from vertical
  • elbow angle: 70�-135�
  • vertical location: 58.5-71.0cm (23.0-28.0inches)
• Monitor
  • primary viewing angle: 0�-60� below horizontal range of adjustment: 12.7cm (5in)
  • shall be >30cm; depends on size of visual target and visual acuity

ANSI/HFS 100-1988: American National Standard for Human Factors Engineering of Visual Display Terminal Work Stations.