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Trunk kinematics and trunk muscle activity during a rapidly applied load.

Authors
Thomas-JS; Lavender-SA; Corcos-DM; Andersson-GB
Source
J Electromyogr Kinesiol 1998 Aug; 8(4):215-225
NIOSHTIC No.
20030587
Abstract
This study investigated the trunk kinematics and electromyographic (EMG) activity of eight trunk muscles when "expected" and "unexpected" loads were applied directly to the torso. Twenty individuals (mean age: 25.1 yr; range 20-33 yr) participated in this mixed model study in which gender was the between-subjects factor, and expectancy and symmetry of the applied load were within-subject factors. The sudden load was delivered to the subject via a cable attached to a thoracic harness and motion was restricted to the lumbar spine by strapping the pelvis to a rigid fixation apparatus. Surface EMG was recorded bilaterally from the longissimus thoracis (LGT), erector spinae (ERS), rectus abdominis (RAB) and the external obliques (EXO). Trunk kinematics were measured with a Lumbar Motion Monitor. During expected loading conditions, the peak muscle activity was reduced for the RAB and EXO bilaterally, and for the ERS(R) (p < 0.01) relative to the unexpected conditions. Conversely, the normalized area of EMG activity prior to the onset of load was increased for the ERS and EXO bilaterally, and for the RAB(R) (p < 0.05) during an expected loading event. Trunk motion in the sagittal and frontal planes was reduced during expected loading. Activation of the trunk muscles just prior to a rapid loading event increases trunk stiffness, decreasing trunk displacement and peak muscle activity.
Keywords
Muscles; Models; Age-factors; Age-groups; Demographic-characteristics; Sex-factors; Biomechanics
CODEN
JEKIE3
Publication Date
19980801
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
1998
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R03-OH-000333
Issue of Publication
4
ISSN
1050-6411
Source Name
Journal of Electromyography and Kinesiology
State
IL
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