Question 4 of 4: Worker Injuries — Office Touch-Screen Use

Question 4: Worker Injuries — Office Touch-Screen Use (20 marks: a–6, b–8, c–6)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Part (a) — Two Work Injury Types

1. Upper-extremity musculoskeletal disorder (e.g. carpal tunnel syndrome / wrist-forearm tendinitis). Repeated finger tapping, dragging, pinch-zooming and scrolling on a touch screen – on top of keyboard and mouse use – involves highly repetitive, small-amplitude finger movements typically performed with the wrist held in extension (bent back) to reach a vertically or near-vertically mounted screen. The human factors concern is the combination of repetition, sustained non-neutral wrist posture and, for a touch screen specifically, the extra static shoulder/forearm loading needed to hold the arm up and reach the screen surface rather than resting on a desk the way keyboard/mouse use allows.

2. Neck and shoulder strain (cervicobrachial/postural overload). Constantly looking at two screens (one likely off to the side or at a different distance/height than the other) plus reaching forward/up to a touch screen produces sustained, static neck flexion/rotation and shoulder elevation held for long periods rather than brief, varying postures. The human factors concern is static muscle loading (isometric holding is more fatiguing per unit of force than dynamic movement) combined with poor screen geometry – height, distance and angle mismatched to a seated worker's neutral gaze and reach zone.

Part (b) — Affected Tasks and Touch-Screen Placement

Determining touch-screen placement. Placement should be derived from the same reach/posture principles used for any primary work display, verified against the touch-specific reach demand: (1) position the touch screen as the primary, most-frequently-used monitor directly in front of the worker (not as a secondary, off-axis screen), since it is described as the one used continuously for document management – this removes the sustained neck rotation identified above; (2) set screen height so the top of the screen is at or slightly below seated eye level, avoiding the neck extension that occurs when a touch target is mounted high enough to also serve as a comfortable visual reference; (3) set screen distance/tilt within the worker's functional (not maximal) reach envelope – close enough that touch gestures do not require full forearm/shoulder extension, and tilted back roughly 20–30° from vertical so tapping the surface does not force full wrist extension the way a vertical screen would; (4) mount on an adjustable arm rather than a fixed desk stand, since the correct height/distance/angle depends on the individual worker's seated anthropometry and chair height, and a one-size placement will not fit the full workforce.

Part (c) — Job Modifications per Affected Task

• Touch-screen tap/drag/pinch-zoom/scroll (wrist/forearm MSD): provide keyboard-shortcut or mouse-based alternatives for the same document actions (save, copy/paste, move) so touch is one option, not the only route, reducing total repetition on the wrist; where the specialised software allows, enable larger touch targets and gesture zones to reduce the precision (and therefore the sustained fine pinch-grip force) each action demands; schedule brief micro-breaks/task rotation away from continuous touch-screen use.
• Keyboard/mouse/stapler use (wrist/forearm MSD): supply an ergonomic keyboard/mouse and a document holder so paper handling does not add extra reach on top of typing; adjust desk/chair height so forearms are roughly horizontal during keyboard use, reducing wrist deviation independent of the touch-screen fix above.
• Dual-monitor viewing (neck/shoulder strain): per Part (b), make the touch screen (the primary-use screen) the direct-ahead monitor and relegate the secondary screen to occasional reference, or provide a monitor arm allowing both screens to be arranged in a shallow arc centred on the worker rather than side-by-side, reducing the rotation angle to either screen.
• Touch-screen reach/dwell (neck/shoulder strain): install the adjustable-arm mount from Part (b) so height/distance/tilt are set per-worker; pair with a sit-stand desk so the worker can periodically vary posture rather than holding one static reach position for the full task duration.