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Effect of trunk flexion on cervical muscle EMG to rear impacts
Author(s) -
Kumar Shrawan,
Ferrari Robert,
Narayan Yogesh
Publication year - 2005
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1016/j.orthres.2005.04.002
Subject(s) - trunk , whiplash , electromyography , physical medicine and rehabilitation , medicine , anatomy , muscle contraction , motor unit recruitment , physical therapy , poison control , biology , ecology , environmental health
Objective: To determine the effect of occupant positioning on the response of the cervical muscles to whiplash‐type posterolateral impacts. Methods: Twenty healthy volunteers underwent left posterolateral whiplash‐type impacts with the volunteers seated “out‐of position”. Electromyograms of the cervical muscles were recorded. Results: Whether having the trunk flexed to the left or right at the time of impact, the muscle responses were low in magnitude, showing a trend to increasing EMG responses with increasing acceleration ( P > 0.05). The time to onset and time to peak electromyogram for most muscles showed a trend to progressively decrease with increasing levels of acceleration. With the subject flexed to the left, all muscles generated 31% or less of the maximal voluntary contraction electromyogram. With the subject flexed to the right, all muscles generated 27% or less of their maximal electromyogram. In both positions, the trapezii were the most active ( P < 0.05). Thus, having the trunk flexed out of neutral posture at the time of impact produces a very low magnitude cervical muscle response compared to impacts with the trunk in neutral posture. Conclusions: In the absence of bodily impact, the flexed trunk posture appears to produce a biomechanical response that would probably decrease the likelihood of cervical muscle injury in low velocity posterolateral impacts. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.