Abstract
Thirty jobs from two manufacturing facilities were analyzed using the Strain Index and a generic risk factor method to determine whether they exposed workers to an increased risk of developing distal upper extremity disorder (hazard classification). If either the right or left side received a Strain Index score of greater than 5 or if the presence of the generic risk factor was noted the job was classified as 'problem.' If both the left or right side had a Strain Index score less than 5 or if the presence of generic risk factors was not noted the job was classified as 'safe.' Morbidity data was collected from the different manufacturing facilities retrospectively over 5 years. Medical records and OSHA 200 logs were used as the main source of morbidity data. If there was recorded upper extremity disorder for a job, the job was classified as 'positive.' Likewise, if there was no recorded disorder the for the job the job was classified as 'safe.' The Strain Index and generic risk factor classifications ('problem' and 'safe') was compared to the morbidity classification ('positive' and 'negative') using a 2x2 table. Strain Index task variables were compared to the morbidity classification to determine which task variables were most significant. The jobs in this study primarily involved light intensities of exertions performed at a 'fair' speed of work for 4-8 hours a day. The task variable that was found to be the comparison of the Strain Index classification and the morbidity classification was highly significant (p <0.001). Using the Strain Index scores as a screening test to identify 'problem' jobs, the sensitivity was 100%, the specificity was 88%, the positive predictive value was 67%, and the negative predictive value was 100%. Generic risk factors were not found to be significant and had low measures of predictive validity. The results generated by this study suggest that the predictive validity of the Strain Index is good and the predictive validity of the generic poor. This indicates that the Strain Index is a valuable tool that can be used in the industrial setting.
Rucker, Nathan Paul (1999). Validation of the strain index in manufacturing facilities. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -R83.