Test-retest repeatability of the Strain Index

Fifteen raters individually, and in five teams of three, evaluated the test-retest repeatability of published data collection and rating methods of the Strain Index by analyzing 61 job video files twice over a 5-month period. Raters estimated average and peak hand forces, measured Duration of Exertion, cycle time, and exertions per job cycle, calculated percent Duration of Exertion and Efforts per Minute, and assigned ratings for five of the six Strain Index task variables. Twelve additional jobs were analyzed to determine Strain Index Score and hazard classification. Intraclass correlation (ICC) coefficients for task variable ratings and accompanying data ranged from 0.66 to 0.95 for both individuals and teams. The Strain Index Score ICC(2,1) for individuals and teams were 0.56 and 0.82, respectively. Intra-rater reliability for the hazard classification was 0.81 for individuals and 0.88 for teams. The results indicate that the Strain Index has good test-retest reliability.