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Inertia artefacts and their effect on the parameterisation of keyboard reaction forces.

Authors
Asundi-K; Johnson-PW; Dennerlein-JT
Source
Ergonomics 2009 Oct; 52(10):1259-1264
NIOSHTIC No.
20035949
Abstract
Reaction force measurements collected during typing on keyboard trays contain inertia artefacts due to dynamic movements of the supporting work surface. To evaluate the effect of these artefacts, vertical forces and accelerations were measured while nine volunteers touch-typed on a rigid desk and a compliant keyboard tray. Two signal processing methods were evaluated: 1) low pass filtering with 20 Hz cut-off; 2) inertial force cancellation by subtracting the accelerometer signal. High frequency artefacts in the force signal, present on both surfaces, were eliminated by low pass filtering. Low frequency artefacts, present only when subjects typed on the keyboard tray, were attenuated by subtracting the accelerometer signal. Attenuation of these artefacts altered the descriptive statistics of the force signal by as much as 7%. For field measurements of typing force, reduction of low frequency artefacts should be considered for making more accurate comparisons across groups using work surfaces with different compliances. Direct measures of physical risk factors in the workplace can improve understanding of the aetiology of musculoskeletal disorders. Findings from this study characterise inertia artefacts in typing force measures and provide a method for eliminating them. These artefacts can add variability to measures, masking possible differences between subject groups.
Keywords
Biomechanics; Computer-equipment; Computers; Computer-software; Ergonomics; Keyboard-operators; Laboratory-testing; Measurement-equipment; Muscles; Musculoskeletal-system; Occupational-exposure; Posture; Standards; Statistical-analysis; Work-areas; Workplace-studies; Work-practices; Author Keywords: exposure assessment tools; physical risk factors; work-related musculoskeletal disorders
Contact
Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115
CODEN
ERGOAX
Publication Date
20091001
Document Type
Journal Article
Funding Amount
121350
Funding Type
Grant
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003997
Issue of Publication
10
ISSN
0014-0139
Source Name
Ergonomics
State
MA
Performing Organization
Harvard University, Boston, Massachusetts
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