Task-Based Measurement of Force in Automotive Assembly Using Worker Self-Assessment, Observational Analysis and Electromyography

Abstract

Worker self-assessments of force and observational assessments are convenient and efficient ways of assessing force demands. Past studies have criticized the accuracy and reliability of these methods of assessment. This study related worker perceptions of peak hand force, observational ratings of peak hand force and peak finger flexor and extensor EMG to understand the reliability and accuracy of these subjective methods when used at a subtask level. Worker and observer ratings of force had moderate correlation (R2 = 0.49). While the correlation of these subjective ratings to peak subtask EMG values was poor at an aggregate level, the percent agreement showed that workers and observers were within 1 point on a 10-point scale at least 61% of the time. This suggests that certain types of tasks were more suited to comparisons with the finger flexor and extensor EMG than others, and further investigation of these relationships is required.

Lean job design and musculoskeletal disorder risk: A two plant comparison

“…Benchmarks and visual cues such as fluidity of motion, use of body weight, facial expressions, unnatural postures, and bulging muscles (Latko, 1997;Marshall & Armstrong, 2004) were used to estimate the subjects' hand force. Force, HAL, and posture were rated by three observers working in pairs (Ebersole & Armstrong, 2002, 2004Ebersole, Lau, & Armstrong, 2005). Agreement between raters was a requirement; for example, if a score between two raters differed by more than 1 point, that risk factor was discussed and re-rated until consensus was reached.…”