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Perceived exertion and discomfort associated with driving screws at various work locations and at different work frequencies.

Ulin-SS; Armstrong-TJ; Snook-SH; Keyserling-WM
Ergonomics 1993 Jul; 36(7):833-846
The perceived exertion and discomfort when driving screws at different work locations and at different work frequencies were investigated. Eighteen subjects (nine males) participated in the exercise which involved driving screws into perforated sheet metal at two horizontal (close and far), and three vertical work locations (elbow, shoulder, and knee), at three different frequencies (eight, ten, and 12 screws per minute (min)). A Borg ten point rating scale was used to assess the perceived exertion for each work location/frequency combination. Discomfort at seven body regions was also ranked for each work location. Results showed that for all three work paces combined, the Borg ratings were highest at knee level and lowest at elbow height, with a difference of 100%. At each work location, at work paces of ten and 12 screws/min, the rating increased 23% to 88%. Ratings during close work were 21% lower than those at the far location. When driving screws at knee height, the torso was identified as the most uncomfortable body part, and the ranking for the torso at knee height was significantly lower than those for the other two vertical locations. Upper leg, wrist, and hand were identified as uncomfortable when driving screws at knee height. At elbow height the most uncomfortable body regions were the wrist and hand. When driving screws at shoulder height the shoulder and upper arm were considered most uncomfortable. No significant difference in discomfort was found between the two horizontal work locations. Ratings at the slowest work pace were 18% to 30% lower than ratings for the other two paces. Borg ratings increased by 25% when work pace increased from 8 to 10 screws/min, and by 12% on increasing to 12 screws/min. Multiple regression analysis showed that both work location and work pace caused increases in the ratings of perceived exertion. The authors conclude that the results can be used as guidelines for workstation design, which would reduce risk of work related fatigue and discomfort.
NIOSH-Publication; NIOSH-Grant; Musculoskeletal-system-disorders; Training; Biomechanics; Ergonomics; Posture; Occupational-hazards; Risk-factors; Task-performance; Work-operations; Author Keywords: Hand tools; Ergonomic design guidelines; Psychophysical assessment
Industrial & Operations Engr University of Michigan 2254 G G Brown Laboratory Ann Arbor, Mich 48109
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University of Michigan at Ann Arbor, Ann Arbor, Michigan