Predicting subjective perceptions of powered tool torque reactions

• Published in: Applied ergonomics 2009, Vol.40 (1), p.47-55
• Main Authors: Lin, Jia-Hua, McGorry, Raymond W.
• Format: Article
• Language: English
• Subjects: Adult; Applied physiology; Biological and medical sciences; Biomechanical Phenomena; Cumulative Trauma Disorders - etiology; Cumulative Trauma Disorders - psychology; Equipment Design; Equipment Safety; Ergonomics; Ergonomics. Work place. Occupational physiology; Exposure assessment; Hand; Hand Strength - physiology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Male; Medical sciences; Models, Statistical; Models, Theoretical; Musculoskeletal diseases; Musculoskeletal Diseases - prevention & control; Musculoskeletal System; Occupational Diseases - etiology; Occupational Diseases - psychology; Occupational Exposure - adverse effects; Perception - physiology; Pilot Projects; Posture - physiology; Power tools; Predictive models; Risk Factors; Torque; Vibration - adverse effects
• ISSN: 0003-6870; 1872-9126
• DOI: 10.1016/j.apergo.2008.01.020

Powered hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders. In this study, subjective ratings of discomfort and acceptability of reaction forces were collected in an attempt to identify their associations with factors such as work location, and response covariates such as grip force and tool handle displacement. Three work configurations using pistol grip and right angle pneumatic nutrunners on horizontal and vertical surfaces were set up in the laboratory. Twenty healthy right-handed male participants operated four tools at nine locations and the corresponding subjective responses were collected. The results indicate that normalized grip force during the torque buildup period was a significant factor for both subjective ratings. For the unacceptable torque reactions across the three tool configurations, the ratio of hand moment impulse over tool torque impulse was significantly greater than for the acceptable reactions. For pistol grip tools used on the vertical surface, as the working height increased 30 cm, the odds of an unacceptable rating over an acceptable rating increased 1.6 times. Prediction models for subjective ratings of discomfort and acceptability provide insight regarding either workstation design or exposure control. These models can further be used to establish exposure limits based on handle displacement and grip force.