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Capability and recruitment patterns of trunk during isometric uniaxial and biaxial upright exertion.

Authors
Sheikhzadeh-A; Parnianpour-M; Nordin-M
Source
Clin Biomech 2008 Jun; 23(5):527-535
NIOSHTIC No.
20034584
Abstract
BACKGROUND: Work-related risk factors of low back disorders have been identified to be external moments, awkward postures, and asymmetrical dynamic lifting amongst others. The distinct role of asymmetry of load versus posture is hard to discern from the literature. Hence, the aim of this study is to measure isometric trunk exertions at upright standing posture at different exertion level and degree of asymmetry to further delineate the effects of exertion level and asymmetry on neuromuscular capability response. METHODS: Fifteen healthy volunteers randomly performed trunk exertions at three levels (30%, 60%, and 100% of maximum voluntary exertion and five different angles (0 degrees , 45 degrees , 90 degrees , 135 degrees , and 180 degrees ) of normalized resultant moments. During each trial, the normalized EMG activity of 10 selected trunk muscles was quantified. FINDINGS: The EMG activity of the 10 trunk muscles was significantly (P<0.001) affected by the level of exertion and angle of normalized resultant moment, and their interactions. The controllability of the torque generation was reduced in biaxial exertions. The capability to generate and control the required trunk moments is significantly lowered during biaxial trunk exertions, while all muscles present higher EMG activity. These results suggest that the trunk muscles will be taxed higher while performing biaxial exertion tasks, increasing muscle fatigue possibly leading to a higher probability of low back injury. INTERPRETATION: The prediction of biaxial trunk performance based on uniaxial data will result in an overestimation of capability and controllability of the trunk during physically demanding tasks. This study provides a better understanding of the potential mechanisms of injury during asymmetrical and biaxial trunk exertion during work-related tasks.
Keywords
Musculoskeletal-system-disorders; Ergonomics; Humans; Biomechanics; Posture; Mathematical-models; Back-injuries; Risk-analysis; Risk-factors
Contact
Ali Sheikhzadeh, The Occupational and Industrial Orthopaedic Center and Program of Ergonomics and Biomechanics, New York University, NYU Hospital for Joint Diseases, 63 Downing Street, New York, NY 10014
CODEN
CLBIEW
Publication Date
20080601
Document Type
Journal Article
Email Address
ali.sheikhzadeh@nyu.edu
Funding Amount
71800
Funding Type
Grant
Fiscal Year
2008
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R03-OH-03087
Issue of Publication
5
ISSN
0268-0033
Priority Area
Musculoskeletal-system-disorders
Source Name
Clinical Biomechanics
State
NY
Performing Organization
Hospital for Joint Diseases Ortho Inst, New York, New York
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