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Electromyography of Superficial and Deep Neck Muscles During Isometric, Voluntary, and Reflex Contractions
MEA Forensic Engineers and Scientists, Richmond, Canada.
School of Human Kinetics, University of British Columbia, Vancouver.
MEA Forensic Engineers and Scientists, Lake Forest, United States.
KTH, School of Technology and Health (STH), Neuronic Engineering.
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2007 (English)In: Journal of Biomechanical Engineering, ISSN 0148-0731, Vol. 129, no 1, 66-77 p.Article in journal (Refereed) Published
Abstract [en]

Increasingly complex models of the neck neuromusculature need detailed muscle and kinematic data for proper validation. The goal of this study was to measure the electromyographic activity of superficial and deep neck muscles during tasks involving isometric, voluntary, and reflexively evoked contractions of the neck muscles. Three male subjects (28-41 years) had electromyographic (EMG) fine wires inserted into the left sternocleidomastoid, levator scapulae, trapezius, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles. Surface electrodes were placed over the left sternohyoid muscle. Subjects then performed: (i) maximal voluntary contractions (MVCs) in the eight directions (45 deg intervals) front the neutral posture; (ii) 50 N isometric contractions with a slow sweep of the force direction through 720 deg; (in) voluntary oscillatory head movements in flexion and extension; and (iv) initially relaxed reflex muscle activations to a forward acceleration while seated on a sled. Isometric contractions were performed against an overhead load cell and movement dynamics were measured using six-axis accelerometry, on the head and torso. In all three subjects, the two anterior neck muscles had similar preferred activation directions and acted synergistically in both dynamic tasks. With the exception of splenius capitis, the posterior and posterolateral neck muscles also showed consistent activation directions and acted synergistically during the voluntary motions, but not during the sled perturbations. These findings suggest that the common numerical-modeling assumption that all anterior muscles act synergistically as flexors is reasonable, but that the related assumption that all posterior muscles act synergistically as extensors is not. Despite the small number of subjects, the data presented here can be used to inform and validate a neck model at three levels of increasing neuromuscular-kinematic complexity: muscles generating forces with no movement, muscles generating forces and causing movement, and muscles generating,forces in response to induced movement. These increasingly complex data sets will allow researchers to incrementally tune their neck models' muscle geometry, physiology, and feedforward/feedback neuromechanics.

Place, publisher, year, edition, pages
ASME , 2007. Vol. 129, no 1, 66-77 p.
Keyword [en]
muscle activity; kinematics; numerical model validation
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-9497DOI: 10.1115/1.2401185ISI: 000243778300009ScopusID: 2-s2.0-34248163533OAI: diva2:114233
QC 20100809Available from: 2008-11-10 Created: 2008-11-10 Last updated: 2010-08-09Bibliographically approved
In thesis
1. 3D Finite Element Modeling of Cervical Musculature and its Effect on Neck Injury Prevention
Open this publication in new window or tab >>3D Finite Element Modeling of Cervical Musculature and its Effect on Neck Injury Prevention
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Injuries to the head and neck are potentially the most severe injuries in humans, since they may damage the nervous system. In accidents, the cervical musculature stabilizes the neck in order to prevent injury to the spinal column and is also a potential site for acute muscle strain, resulting in neck pain. The musculature is consequently an important factor in the understanding of neck injuries. There is however a lack of data on muscle response and little is known about the dynamics of the individual muscles. In this thesis the numerical method of Finite Elements (FE) is used to examine the importance of musculature in accidental injuries. In order to study the influence of a continuum musculature, a 3D solid element muscle model with continuum mechanical material properties was developed. It was hypothesized that a 3D musculature model would improve the biofidelity of a numerical neck model by accounting for the passive compressive stiffness, mass inertia, and contact interfaces between muscles. A solid element representation would also enable the study of muscle tissue strain injuries.

A solid element muscle model representing a 50th percentile male was created, based on the geometry from MRI, and incorporated into an existing FE model of the spine. The passive material response was modeled with nonlinear-elastic and viscoelastic properties derived from experimental tensile tests. The active forces were modeled with discrete Hill elements. In the first version of the model the passive solid element muscles were used together with separate active spring elements. In the second version the active elements were integrated in the solid mesh with coincident nodes. This combined element, called the Super-positioned Muscle Finite Element (SMFE), was evaluated for a single muscle model before it was incorporated in the more complex neck muscle model. The main limitation of the SMFE was that the serial connected Hill-type elements are unstable due to their individual force-length relationship. The instabilities in the SMFE were minimized by the addition of passive compressive stiffness from the solid element and by the decreased gradient of the force-length relation curve.

 The solid element musculature stabilized the vertebral column and reduced the predicted ligament strains during simulated impacts. The solid element compressive stiffness added to the passive stiffness of the cervical model. This decreased the need for additional active forces to reproduce the kinematic response of volunteers during impact. The active response of the SMFE improved model biofidelity and reduced buckling of muscles in compression. The solid element model predicted forces, strains, and energies for individual muscles and showed that the muscle response is dependent on impact direction and severity. For each impact direction, the model identified a few muscles as main load carriers that corresponded to muscles generating high EMG signals in volunteers. The single largest contributing factor to neck injury prediction was the muscle active forces. Muscle activation reduced the risk of injury in ligaments in high-energy impacts. The most urgent improvements of the solid element muscle model concerns: the stability of the SMFE; the boundary conditions from surrounding tissues; and more detailed representations of the myotendinous junctions. The model should also be more extensively validated for the kinematical response and for the muscle load predictions.

It was concluded that a solid muscle model with continuum mechanical material properties improves the kinematical response and injury prediction of a FE neck model compared to a spring muscle model. The solid muscle model can predict muscle loads and provide insight to how muscle dynamics affect spinal stability as well as muscle acute strain injuries.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. vii, 60 p.
Trita-STH : report, ISSN 1653-3836 ; 2008:6
Finite Element, Cervical Musculature, Neck injury prediction, Continuum Mechanics, Solid Elements
National Category
Engineering and Technology
urn:nbn:se:kth:diva-9503 (URN)978-91-7415-180-0 (ISBN)
Public defence
2008-12-05, 3-221, Alfred Nobels Allé 10, Huddinge, 13:00 (English)
QC 20100809Available from: 2008-11-17 Created: 2008-11-10 Last updated: 2010-08-09Bibliographically approved

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