Methods to assess physical load at work : With a focus on the neck and upper extremities

To prevent work-related musculoskeletal disorders (MSDs), useful, reliable and valid methods for assessing physical workload and risks for MSDs are needed. Ergonomists often assess work by short visual observations without a specific tool. A branch-specific tool was developed for assessing working technique during cash register work (BAsiK observation protocol). Inclinometers are an alternative for assessing upper arm postures - over several days. Ergonomists need guidelines explaining how to analyze and interpret such data. The aim was to examine and investigate methods for assessing physical load at work, with focus on the neck and upper extremities. In Paper: I, the reliability and criterion validity of the BAsIK observation protocol were assessed. II, the reliability of risk assessments of repetitive work, based on visual observations performed by 21 ergonomists without a specific tool, was assessed. III, whole-day inclinometer measurements of upper arm elevation were compared between work and leisure, across 13 different occupations – before and after arm elevations during sitting time was excluded. IV, the association between inclinometer-based upper arm elevation and neck/shoulder pain was assessed among 654 blue-collar workers. The intra-observer reliability of the BAsIK protocol was deemed acceptable, but only 3 of 10 questions in the protocol showed acceptable inter-observer reliability, and 3 showed acceptable criterion validity. Neither the inter- or intra-observer reliability of risk assessment without any specific method was acceptable for any upper body regions. None of the occupation groups, in paper III, had higher proportion of time with arm elevation during work than leisure. However, when arm elevation during sitting was excluded, 8 occupation groups had higher proportion of time with elevated arms during work than leisure. Whole-workday inclinometer-based upper arm elevation was not associated with neck/shoulder pain within the assessed population. The results indicate that, in most cases, a single visual observation of a work sequence is not a reliable means of assessing repetitive work. A large proportion of arm elevation may derive from sitting time. At low exposure levels, arm elevation per se may not be a risk factor for neck/shoulder pain. This must be taken into account when evaluating the risk for MSDs