A comparison of exposure to risk factors in *construction trades with high and low prevalence of carpal tunnel syndrome

Recent evidence suggests that carpal tunnel syndrome (CTS) has a high prevalence in construction workers, with the prevalence in heavy equipment operators approximately 7%, and in heavy equipment mechanics 27%. Little is known about construction worker's exposure to physical risk factors and the effect on CTS, since this work is non-cyclic and highly variable. Therefore, the purpose of this study was to assess the factors that may be related to CTS using direct and prolonged measurement methods, and to develop a novel method of directly measuring exposure to forceful exertions of the hand and wrist. It was hypothesized that mechanics are exposed to more forceful exertions than operators, and that operators work at lower levels of intensity of forceful exertions than mechanics.;The activity from the dominant finger flexors of 24 operators and 24 mechanics was sampled with surface electromyography (EMG), using a portable data logger, for approximately one hour of normal work. The EMG data was reduced with exposure variation analysis, and clustered exposure variation analysis (CEVA), a new method of describing work exposure. Six categories of CEVA were evaluated consisting of interactions between high, moderate and low intensity, and short and prolonged durations of forceful exertions.;The results indicated that mechanics spent 9% of their sampled work time performing high intensity-short duration contractions, contrasted to only 2% for operators (p < 0.001). Mechanics spent 19% of the time performing moderate intensity-short duration contractions, contrasted to 7% for operators (p < 0.001). Operators spent a disproportionate amount of work time with either low levels of forceful exertion or resting their flexor forearm.;The findings indicate that mechanics have much greater exposure to forceful exertions of the hand and wrist than operators, which may explain the greater prevalence of CTS in mechanics. This study is one of very few that has directly quantified exposure to physical risk factors in highly variable, non-cyclic work. The combination of CEVA and data logging is a precise and easily applied direct, field exposure assessment technique that is able to evaluate multiple dimensions of exposure, including temporal factors, during highly variable non-cyclic tasks.