Assessment of physical demands and comparison of multiple exposure definitions in a repetitive high risk sawmill occupation: Saw-filer

Abstract

Aims The aims of this study are to: (1) describe the physical exposures which have resulted in a high incidence of upper extremity musculoskeletal injuries by multiple posture, exertion and frequency variable definitions and (2) examine the comparability of those multiple variable definitions. Scope The physical exposures of 15 saw-filers in four sawmill facilities were recorded using surface electromyography and electrogoniometry. Results Sixty percent of subjects reported greater then moderate discomfort in the task dominant upper extremity. Peak joint excursions of 55°, 98° and 83° in the planes of wrist radial/ulnar deviation, flexion/extension and pronation/supination were required to perform the job. Total joint range of motion was significantly different ( p < . 01 ) dependent upon the definition of end range used. Performance of the primary job task (hammering saws) required an average of 10% MVC of the forearm musculature assessed and was performed an average of 32 times per minute. Percentage of maximum voluntary contraction was not associated with either Borg or visual analog scale measures of exertion. Average repetitions performed per day ranged from 3036 to 20,950 dependent upon facility. Conclusions Our findings indicate the definitions of posture and exertion examined here are not comparable. Calculation of ergonomic risk assessments based on quantified exposure information by multiple definitions is now necessary to examine the effect of variable definition on model output and predictive validity. Relevance to industry Collection of quantified physical exposure information allows many definitions of the exposure variable to be used. Understanding of the relationship between commonly used exposure variable definitions is necessary before applying ergonomic risk assessments to direct industrial prevention efforts.