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Wrist posture affects hand and forearm muscle stress during tapping.

Authors
Qin-J; Chen-H; Dennerlein-JT
Source
Appl Ergon 2013 Nov; 44(6):969-976
NIOSHTIC No.
20044285
Abstract
Non-neutral wrist posture is a risk factor of the musculoskeletal disorders among computer users. This study aimed to assess internal loads on hand and forearm musculature while tapping in different wrist postures. Ten healthy subjects tapped on a key switch using their index finger in four wrist postures: straight, ulnar deviated, flexed and extended. Torque at the finger and wrist joints were calculated from measured joint postures and fingertip force. Muscle stresses of the six finger muscles and four wrist muscles that balanced the calculated joint torques were estimated using a musculoskeletal model and optimization algorithm minimizing the squared sum of muscle stress. Non-neutral wrist postures resulted in greater muscle stresses than the neutral (straight) wrist posture, and the stress in the extensor muscles were greater than the flexors in all conditions. Wrist extensors stress remained higher than 4.5 N/cm² and wrist flexor stress remained below 0.5 N/cm² during tapping. The sustained high motor unit recruitment of extensors suggests a greater risk than other muscles especially in flexed wrist posture. This study demonstrated from the perspective of internal tissue loading the importance of maintaining neutral wrist posture during keying activities.
Keywords
Biomechanics; Muscle-function; Musculoskeletal-system; Hand-injuries; Posture; Risk-factors; Force; Biomechanical-modeling; Models; Musculoskeletal-system-disorders; Keyboard-operators; Computer-equipment; Arm-injuries; Overloading; Muscle-stress; Muscle-tissue; Humans; Physiological-measurements; Physiological-testing; Author Keywords: Biomechanical model; Muscle stress; Optimization; Tapping
Contact
Jack T. Dennerlein, Harvard School of Public Health, Department of Environmental Health, 401 Park Drive, Room 404L, Boston, MA 02215
CODEN
AERGBW
Publication Date
20131101
Document Type
Journal Article
Email Address
jax@hsph.harvard.edu
Funding Type
Grant
Fiscal Year
2014
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-008373; Grant-Number-T42-OH-008416
Issue of Publication
6
ISSN
0003-6870
Source Name
Applied Ergonomics
State
MA
Performing Organization
Harvard University School of Public Health
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