Rapid Upper Limb Assessment (RULA) for Ergonomic Decision Making in Welding Postures

Abstract

Awkward welding postures were commonly associated with high ergonomic risk, but changes in Rapid Upper Limb Assessment (RULA) scores could also have reflected observer variability. This experimental study assessed whether RULA improvements after ergonomic intervention exceeded observed scoring variability. Sixteen welding conditions, including flat, horizontal, vertical, overhead, fixed-pipe, 45°-pipe, and site-constrained tasks, were evaluated before and after interventions involving work-height adjustment, workpiece rotation, arm support, ergonomic seating, and stable platforms. Observer variability was quantified from 40 RULA assessments of five reference postures. The mean RULA score decreased from 6.56 ± 1.03 to 3.88 ± 1.26, representing a 40.9% reduction. Ergonomic risk decreased in 15 of 16 conditions, and the number of maximum RULA scores of 7 decreased from 12 to zero. Exact observer agreement was 60.0%, with a mean absolute error of 0.575 and a 90th-percentile error of 2 points. These findings indicated that RULA provided stronger evidence of ergonomic improvement when score reductions exceeded observer-related variability.