Test-retest repeatability of the Strain Index.

Area of Science:

• Ergonomics and Occupational Health
• Industrial Hygiene
• Human Factors Engineering

Background:

• The Strain Index is a tool used to assess the risk of musculoskeletal injuries in occupational settings.
• Reliability of assessment tools is crucial for accurate risk evaluation and intervention planning.
• Previous assessments of the Strain Index's repeatability were limited.

Purpose of the Study:

• To evaluate the test-retest repeatability of the Strain Index's data collection and rating methods.
• To assess the reliability of Strain Index scores and hazard classifications.
• To compare the reliability of individual raters versus teams of raters.

Main Methods:

• Fifteen raters (individually and in teams of three) analyzed 61 job videos twice over 5 months.
• Raters collected data on hand forces, exertion duration, cycle time, and exertions per cycle.
• Strain Index task variables, Strain Index Score, and hazard classifications were determined.

Main Results:

• Intraclass correlation (ICC) coefficients for task variable ratings ranged from 0.66 to 0.95.
• Strain Index Score ICC(2,1) was 0.56 for individuals and 0.82 for teams.
• Intra-rater reliability for hazard classification was 0.81 (individuals) and 0.88 (teams).

Conclusions:

• The Strain Index exhibits good test-retest reliability for evaluating job tasks.
• Team-based ratings showed higher reliability for the Strain Index Score compared to individual ratings.
• The findings support the use of the Strain Index as a reliable tool in ergonomic assessments.