Variability in muscle activity measurements among clinical ophthalmologists

Limited information is available describing ergonomics issues and physical risk factors for work-related musculoskeletal pain in the eye care clinical environment. The purpose of this thesis was to estimate the distribution of exposure to forceful muscular exertion of neck and shoulder muscles, and to estimate the relative contribution of important components of exposure variance to overall exposure variance. Surface electromyography (EMG) was used to continuously collect muscle activity measurements of the right and left upper trapezius muscles as well as the right and left anterior deltoid muscles throughout two full working days in clinical ophthalmology.

The study observed between-exam-within-day-within-subject to be the variance component with the greatest contribution to total exposure variance in most EMG summary measures. For example, 52.1% of the exposure variability could be attributed to the exam and only 18.7% attributable to the day for the mean RMS value of the right upper trapezius. Similar results were found in the left anterior deltoid muscle with 52.7% exposure variability attributable to the exam and 15.7% attributable to the day. For futures investigations, the large between-exam variance implies the need for longer measurement durations in order to obtain more exams and to explore deeper into the physical risk factors the exams.