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The influence of lift frequency, lift duration and work experience on discomfort reporting.

Authors
Parakkat-J; Yang-G; Chany-AM; Burr-D; Marras-WS
Source
Ergonomics 2007 Mar; 50(3):396-409
NIOSHTIC No.
20032041
Abstract
Discomfort surveys are commonly used to assess risk in the workplace and prioritize jobs for interventions before an injury or illness occurs. However, discomfort is a subjective measure and the relationship of discomfort to work-related factors is poorly understood. The objective of this study was to understand how reports of discomfort relate to work-related risk factors for the low back. A total of 12 novice and 12 experienced manual materials handlers performed repetitive, asymmetric lifts at different load levels and at six different lift frequencies throughout an 8-h exposure period. Discomfort was recorded hourly throughout the day. Analyses were performed to determine which experimental factors influenced reporting of discomfort and if discomfort trends matched spine loading trends. Novice lifters reported significantly higher discomfort levels than experienced subjects. They also reported increases in discomfort as moment exposure increased and as the exposure time increased. Novices lifting at 8 Nm load moment level reported increased discomfort from 0.07 to 0.63 by the end of the day, at 36 Nm they reported an increase from 0.04 to 0.40 and at 85 Nm they reported an increase from 0.37 to 3.06. Experienced subjects, on the other hand, reported low levels of discomfort regardless of moment exposure, lift frequency or exposure duration. The reported discomforts were generally unrelated to the biomechanical loading on the spine. Discomfort reporting appears to be more a reflection of experience than of work risk factor exposure. Experienced subjects may have more efficient motor patterns, which reduce spinal load and thus discomfort. Novice subjects seemed to have a lower threshold of discomfort. Caution is needed when using discomfort reporting as a means to identify jobs in need of interventions, in that biomechanical loading may not be accurately represented. Discomfort should only be used as a supplement to objective measures, such as spinal loading, to assess the risk of low back disorders.
Keywords
Biomechanics; Manual-lifting; Manual-materials-handling; Materials-handling; Exposure-levels; Exposure-assessment; Ergonomics; Back-injuries; Risk-analysis; Risk-factors; Musculoskeletal-system-disorders; Skeletal-disorders; Skeletal-system; Skeletal-system-disorders
Contact
Biodynamics Laboratory, The Ohio State University, 1971 Neil Ave., Columbus, OH 43210
CODEN
ERGOAX
Publication Date
20070301
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2007
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003913
Issue of Publication
3
ISSN
0014-0139
Source Name
Ergonomics
State
OH
Performing Organization
Ohio State University, Columbus, Ohio
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