¹Department of Epidemiology and Global Health, Umeå University, Umeå, Sweden
²Department of Clinical Science, Intervention and Technology - CLINTEC, Stockholm, Sweden
³IMM Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
⁴School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden

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Introduction: A large body of occupational epidemiologic findings shows associations between neck/shoulder disorders and biomechanic exposures (as awkward postures and repetitive movements) of the shoulders. Recommended limit values on the duration of working with elevated arms (>30° for 50% and >60° for 10% of the workday) and movement velocity (median velocity of 60°/s) has been suggested. Most of the evidence is based on subjective ratings of postures and has not focused on older workers. However, with today’s prolonged working life, older workers in manual jobs may constitute a risk group. The aim of this study was therefore to assess shoulder workload in older workers in four physically demanding occupational groups using technical measurements.

Methods: Right upper arm postures and movements were measured using inertial measurement units during three full workdays in construction workers (n=35), kitchen workers (n=37), cleaners (n=29) and assistant nurses (n=26) over the age of 50. Elevation angle and angular velocity were calculated. Mean values and variance components within and between subjects were estimated for the whole working day in one-way random effect models using restricted maximum likelihood algorithms. One-way ANOVA tests were conducted to compare the assessed exposure variables between the different groups.

Results: The median elevation angle was similar between the occupational groups (22°–23°), while the 90th percentile was significantly higher in construction workers compared to the other occupational groups (54° vs. 45–49°). Construction workers worked with their right arm elevated longer than the other occupational groups (>60° 8% vs. 4–6% and >90° 3% vs. 1%). In total, 15% of the measured days were spent elevated >60° above the recommended limits and none of measured days were above the recommend limit on median angular velocity. The mean median movement velocity of the right arm was 18, 25, 29, and 14°/s for construction workers, kitchen workers, cleaners and assistant nurses respectively. On average, kitchen workers and cleaners spent more time with fast movements (>90°/s) of the right arm (11% and 13% respectively) compared to construction workers (7%) and assistant nurses (9%), they also spent less time in rest (<20° and <5°/s, 12% and 13% vs. 18% and 23%). We found considerable variability both between subjects and within the subjects.

Discussion: The construction workers in our study spent slightly less time with elevated arms than older construction workers in a Danish study but more than hairdressers in a Swedish study. The time with elevated arms for the cleaners and assistant nurses was similar to other studies.

Conclusion: Construction workers spend more time with their arms elevated, while kitchen workers and cleaners have faster arm movements. There was also a substantial variation between individuals within each occupational group and between days. No occupational group reached the proposed action level for time with elevated arms on a group level, but single-measured days often exceeded this level.