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Effects of shoulder, low back, or knee strength degradation on motion control strategies and injury risk during manual materials handling.

Zhang-X; Bartlett-D; Li-K; Riemer-R
Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, K01-OH-007838, 2008 Mar; :1-49
The objective of this research grant was to systematically investigate if and how dynamic (isokinetic) muscular strengths in three major body joints (the shoulder, low back, and knee) affect injury risk associated with manual materials-handling. Our long-term goal is to develop quantitative tools and guidelines that integrate the measurable strength and movement information for the recognition, prediction, and prevention of occupational musculoskeletal injuries. We first evaluated the dynamic (isokinetic) strengths of human subjects, and established a sizable dynamic strength databases with various stratification schemes; we designed and conducted a unique simulated manual materials-handling experiment to investigate subjects' batch-assorting strategy and lifting kinematics under various task conditions created by varying load-handled, body symmetry, and knowledge of strength. We identified a relationship between dynamic isokinetic strength and the batch-assorting strategy. This was done to initiate a manual materials-handling task and an effect of self-knowledge of the strength on that relationship. We also discovered that relative strength between the back and knees can differentiate and predict lifting biomechanics: persons with back strength greater than their total knee strength tended to use a back lift strategy, and vice versa. We did not find any significant difference in dynamic strength between asymptomatic individuals and self-claimed symptomatic individuals with select joint (shoulder, back, or knee) pain. The results of this study rendered important practical implications on the utility of isokinetic strength tests in worker selection or screening. It also indicated on how job training and design should be conducted to better prevent injuries incurred during manual materials-handling and on incorporation of strength factor in digital human modeling (DHM) technology for ergonomics and design.
Muscle-physiology; Musculoskeletal-system; Physical-capacity; Physical-stress; Physiological-factors; Ergonomics; Biomechanics; Back-injuries; Manual-materials-handling; Injury-prevention
Xudong Zhang, Orthopaedic Research Laboratory, University of Pittsburgh, 3820 South Water Street, Pittburgh, PA 13203
Publication Date
Document Type
Final Grant Report
Funding Type
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
NIOSH Division
Priority Area
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Source Name
Effects of Shoulder, Low Back, or Knee Strength Degradationon Motion Control Strategies and Injury Risk During Manual Materials Handling
Performing Organization
University of Illinois Urbana-Champaign