Objectives To quantify the relationship between workplace physical factors, particularly hand activity level (HAL) and forceful exertion and carpal tunnel syndrome (CTS), while taking into account individual factors. To compare quantitative exposure assessment measures with more practical ratings-based measures.

Methods In a group of healthcare and manufacturing workers, each study participant's job tasks were evaluated for HAL, forceful exertion and other physical stressors and videotaped for further analysis, including frequency and duration of exertion and postural deviation. Electrodiagnostic testing of median and ulnar nerves and questionnaires were administered to all participants. A CTS case required median mononeuropathy and symptoms on hand diagrams in fingers 1–3. Multiple logistic regression models were used to analyse associations between job and individual factors and CTS.

Results Of 477 workers studied, 57 (11.9%) were dominant hand CTS cases. Peak force ≥70% maximum voluntary contraction versus <20% maximum voluntary contraction resulted in an OR of 2.74 (1.32–5.68) for CTS. Among those with a body mass index ≥30, the OR for ≥15 exertions per minute was 3.35 (1.14–9.87). Peak worker ratings of perceived exertion increased the odds for CTS by 1.14 (1.01–1.29) for each unit increase on the 10-point scale. The odds for CTS increased by 1.38 (1.05–1.81) for each unit increase on the HAL 10-point scale among men, but not women. Combined force and HAL values above the ACGIH TLV for HAL resulted in an OR of 2.96 (1.51–5.80) for CTS.

Discussion/Conclusions Quantitative and ratings-based job exposure measures were each associated with CTS. Obesity increased the association between frequency of exertion and CTS.