Upper limb dynamic responses to impulsive forces for selected assembly workers

Mary E. Sesto, Robert G. Radwin, Walter F. Block, Thomas M. Best

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


This study evaluated the upper limb, dynamic, mechanical response parameters for 14 male assembly workers recruited from selected jobs based on power tool use. It was hypothesized that the type of power tool operation would affect stiffness, effective mass, and damping of the upper extremity; and workers with symptoms and positive physical examination findings would have different mechanical responses than asymptomatic workers without physical examination findings. Participants included operators who regularly used torque reaction power hand tools, such as nutrunners and screwdrivers, and nontorque reaction power hand tools, such as riveters. The mechanical parameters of the upper limb were characterized from the loading response of an apparatus having known dynamic properties while worker grasps an oscillating handle in free vibration. In addition, all workers underwent a physical examination, magnetic resonance imaging, and completed a symptom survey. Workers were categorized as controls or cases based on reported forearm symptoms and physical exam findings. A total of seven workers were categorized as cases and had less average mechanical stiffness (46%, p < 0.01), damping (74%, p < 0.01), and effective mass (59%, p < 0.05) than the seven workers categorized as controls. Magnetic resonance imaging (MRI) findings suggestive of muscle edema were observed for two workers classified as cases and who regularly used torque reaction power tools. No MRI enhancement was observed in the seven subjects who did not regularly use torque reaction power tools. The ergonomic consequences of less stiffness, effective mass, and damping in symptomatic workers may include reduced capacity to react against rapidly building torque reactionforces encountered when operating power hand tools.

Original languageEnglish (US)
Pages (from-to)72-79
Number of pages8
JournalJournal of Occupational and Environmental Hygiene
Issue number2
StatePublished - Feb 1 2006
Externally publishedYes


  • Forearm
  • Magnetic resonance imaging
  • Mechanical model
  • Power tool use
  • Stiffness
  • Work-related musculoskeletal disorders

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health


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