Investigation of observational methods assessing workload of static working postures based on surface electromyography.
Tobias Hellig, Vera Rick, Alexander Mertens and 2 others
PMID 30829630WHAT IT FOUND
OWAS and EN 1005-4 posture ratings matched some muscles but not others in 24 young adults holding static postures.
OWAS did not track deltoid muscles; EN 1005-4 shoulder zones tracked erector spinae and lower trapezius.
Key findings
01In 24 volunteers, increasing trunk inclination and shoulder flexion raised muscle activity, and the two angles interacted.
02OWAS action categories correlated with muscle activity for all muscles except the anterior deltoid muscles.
03EN 1005-4 shoulder assessment correlated with muscle activity of erector spinae and lower trapezius, and negatively with right anterior deltoid.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study was done in a controlled laboratory, not at real workplaces. The work-rest cycle used here, one minute of static posture followed by one minute of rest, does not match typical work patterns. The study did not test dynamic movements, lifting, or external forces. The sample was small, with 24 volunteers, and they were aged 20 to 28, so it may not represent older or injured workers. Only postures in the sagittal plane were tested. The study compared posture ratings with surface EMG; it did not test whether these methods prevent or treat musculoskeletal disorders in patients.
Declared interests
The authors declared no conflicts of interest. The study was funded by the German Federal Ministry of Education and Research (grant 16SV6143).
The easy way to misread this
Do not conclude that OWAS or EN 1005-4 are validated for patient care or real workplace injury prevention. The study tested only 24 young adults holding static postures in a lab, and it compared posture ratings with muscle activity, not with symptoms, diagnosis, or patient outcomes.