Work-related musculoskeletal disorders (MSDs) remain the leading cause of occupational disability worldwide, yet traditional ergonomic risk assessments are often limited by subjectivity and inter-rater variability. This study evaluated the validity of Etiscope, a risk assessment system that uses wearable sensors and quantitative risk scoring methods derived from the Australian Model Code of Practice – Hazardous Manual Tasks 2016.

A panel of 25 professional ergonomists independently conducted 152 risk assessments across 76 workplace task videos spanning retail, postal, mining, and meat-processing industries. Risk assessments generated by the Etiscope system were compared against expert assessments using Kolmogorov–Smirnov distribution testing and inter-rater agreement analyses.

No significant difference was observed between the overall distribution of risk scores generated by Etiscope and those assigned by expert ergonomists, indicating comparable overall risk classification performance. However, substantial variability existed between individual ergonomists, highlighting the inherent subjectivity of the professional human standard of risk assessment. Detailed analysis of risk scoring categories identified systematic differences between ergonomists and the Etiscope system. Etiscope identified significantly higher risk scores associated with neck actions, whereas ergonomists assigned significantly higher risk scores for complex actions (several actions occurring concurrently).

To explain these findings, further analysis into ergonomist-to-ergonomist variability revealed strong disagreement when identifying risk associated with neck actions. This variability demonstrates the difficulty in determining the degree of flexion, extension and twisting in such a compact and complex anatomical location, using observational methods. In contrast, ergonomists strongly agreed when identifying more complex actions than the Etiscope system, erring on the side of caution while Etiscope was stricter in its risk identification.

This highlights in what respects the Etiscope system is best placed to aid ergonomists in assessing risk of work-related tasks, demonstrating how it assesses the distinct action classes compared to professionals.