Question 4 of 4: Worker Injuries — Carpal Tunnel Syndrome (Part B, choose 1 of 2)

Question 4: Worker Injuries — Carpal Tunnel Syndrome (Part B, choose 1 of 2) (20 marks: a–5, b–10, c–5)

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) — What CTS is, and why it matters. Carpal tunnel syndrome is a compressive neuropathy of the median nerve as it passes through the carpal tunnel — a narrow passage on the palm side of the wrist bounded by the carpal bones and the transverse carpal ligament, through which the median nerve and nine finger flexor tendons all pass. Repetitive or forceful wrist flexion/extension, sustained awkward wrist postures, vibration and high-force pinch/grip gradually increase pressure inside the tunnel and/or cause tendon swelling, which compresses the median nerve and produces numbness, tingling and pain in the thumb, index, middle and part of the ring finger, weakened grip, and eventually muscle wasting at the base of the thumb if untreated. It is a central concern in human factors because it is one of the most common and costly work-related musculoskeletal disorders, it is directly and predictably driven by task design (posture, force, repetition, duration) rather than being an unavoidable consequence of manual work, and because it is largely preventable through ergonomic task and tool redesign — making it a textbook case for proactive human factors intervention rather than after-the-fact treatment.

Part (b) — Effect of each task on a CTS sufferer, and which is worst. (a) Rapid data entry with a keyboard: sustained, highly repetitive finger flexion with the wrist often held in extension (bent back) against the desk/keyboard edge — a classic CTS-aggravating combination of repetition and awkward wrist posture, though typically at low individual finger force. (b) Plucking a chicken: repetitive, forceful pinch-and-pull gripping with the wrist frequently deviated (bent sideways) to reach and pull at different angles — combines high force with repetition and ulnar/radial deviation, all independently implicated in CTS. (c) Playing a piano: repetitive finger movement but generally low force and a relatively neutral wrist posture for a trained player — the lowest-risk task of the five for CTS specifically (though it carries its own overuse-injury profile). (d) Kneading dough: sustained, high-force wrist flexion/extension and forearm pronation applied repeatedly against resistance — combines high force, repetition and sustained non-neutral wrist posture. (e) Painting a ceiling: sustained overhead arm elevation with the wrist often extended to control the brush/roller angle against gravity — static shoulder loading is the dominant concern here, with only moderate wrist repetition/force compared to the other tasks. Greatest impact: kneading dough has the greatest impact on CTS symptoms, because it uniquely combines all three primary CTS risk factors at once and at high intensity — high force (working stiff dough against resistance), high repetition (continuous folding/pressing cycles), and sustained non-neutral wrist posture (repeated flexion/extension with pronation) — whereas the other tasks are each missing or moderate on at least one of those three factors (data entry is low-force, piano is low-force with a fairly neutral wrist, painting a ceiling loads the shoulder more than the wrist, and plucking is forceful/repetitive but with less sustained flexion than kneading).

Part (c) — Job modifications for each task. (a) Data entry: provide a keyboard tray/wrist rest that keeps the wrist neutral (not extended), use a split or negative-tilt keyboard, and schedule micro-breaks/task rotation to interrupt sustained repetition. (b) Plucking a chicken: introduce mechanical/semi-automated plucking equipment to remove the repetitive forceful pinch from the worker, or rotate workers frequently between plucking and a dissimilar low-force task, and provide ergonomic-grip tools that reduce the pinch force needed. (c) Piano: already comparatively low-risk; recommend adjustable bench height/reach to keep the wrist neutral and normal practice-break scheduling to manage general overuse. (d) Kneading dough: mechanize kneading with a stand mixer/dough hook for high-volume production, or if hand-kneading must remain, limit continuous kneading duration, rotate the task frequently, and use forearm/whole-arm body weight technique rather than wrist-force alone to reduce isolated wrist loading. (e) Painting a ceiling: use extension poles to bring the work to a more neutral arm/wrist height instead of prolonged overhead reach, and schedule frequent rest breaks to relieve the sustained static shoulder/wrist loading. Across all five, the common modification theme is the same: remove or mechanize the forceful/repetitive/awkward-posture element rather than asking the worker to "push through" or simply work more carefully, since CTS in this population is generally an existing, worsening condition rather than a fresh, preventable one.