Electromyography of Superficial and Deep Neck Muscles During Isometric, Voluntary, and Reflex Contractions

[+] Author and Article Information
Gunter P. Siegmund

 MEA Forensic Engineers & Scientists, Richmond, BC, V7A 4S5 Canada; School of Human Kinetics, University of British Columbia, Vancouver, BC, V6T 1Z1, Canadagunter.siegmund@meaforensic.com

Jean-Sébastien Blouin

School of Human Kinetics, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada

John R. Brault

 MEA Forensic Engineers & Scientists, Lake Forest, CA 92630

Sofia Hedenstierna

Division of Neuronic Engineering, Royal Institute of Technology, 141 57 Huddinge, Sweden

J. Timothy Inglis

School of Human Kinetics, University of British Columbia, Vancouver, BC, Canada; International Collaboration on Repair Discovery, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada

J Biomech Eng 129(1), 66-77 (Jul 06, 2006) (12 pages) doi:10.1115/1.2401185 History: Received October 26, 2005; Revised July 06, 2006

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 (2841years) 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 (45deg intervals) from the neutral posture; (ii) 50N isometric contractions with a slow sweep of the force direction through 720deg; (iii) 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.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 9

Normalized rms EMG and kinematics of the head, T1 and head with respect to T1 for forward sled tests experienced by subjects 1 (left), 2 (middle), and 3 (right). Dashed vertical lines aligned with peak horizontal acceleration (ax) of the head with respect to T1. Muscle scale bars indicate 100% of maximal voluntary contractions (MVCs).

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Figure 1

Axial MR images at the C4 level of the three subjects. Shown are: (a) a fast field echo (FFE) scan of Subject 1; (b) a proton density (PD) scan of Subject 2; and (c) a T1-weighted scan of Subject 3. All three types of scans were acquired from each subject and all scans were acquired in the supine position.

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Figure 2

Location of wire insertions into the neck muscles. Insertions shown on right side for clarity only; all wires inserted only on left side.

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Figure 3

Schematic showing: (a) the head clamp and force plate used for the isometric contractions; (b) the transducers and reference frames used for the voluntary movements and sled tests; and (c) the sled configuration.

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Figure 4

Superposition of the sled acceleration pulses for the three subjects (solid lines) and a vehicle-to-vehicle collision pulse (dashed line) with a speed change of 8km∕h recorded during earlier experiments (48).

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Figure 5

Horizontal force (top row) and directional muscle tuning curves (bottom four rows) for each subject (left three columns), and the mean response of all subjects (right column). Scale and direction shown at top left. All muscle activation levels normalized to the maximum value (100%) for that particular subject’s muscle.

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Figure 6

Horizontal force (top row) and tuning curves (bottom four rows) for sternohyoid (STH), sternocleidomastoid (SCM), levator scapulae (Lev Scap), and trapezius (Trap) during the 50N isometric force sweeps. The dashed circle in the force plots (top row) indicates 50N. Clockwise (+z) sweeps shown with a thick line and counterclockwise (−z) sweeps shown with a thin line.

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Figure 7

Tuning curves for splenius (SPL), semispinalis capitis (SsCap), semispinalis cervicis (SsCerv), and multifidus at the C4 (MultC4) and C6 (MultC6) levels during the 50N isometric sweeps (continuation of Fig. 6). Clockwise (+z) sweeps shown with a thick line, and counterclockwise (−z) sweeps shown with a thin line.

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Figure 8

Normalized rms electromyographic recordings (scale bar=100% MVC) and kinematics of the head with respect to T1 for voluntary head flexion/extension movements executed by subjects 1 (left), 2 (middle), and 3 (right). Sync refers to an acoustic signal heard by the subjects. The head is extended and being accelerated in the flexion direction during time interval AB between the left two dashed vertical lines, and the head is flexed and being accelerated in the extension direction during time interval BC (* increase in baseline noise for SsCap in Subject 1 after sled test but before flexion/extension movement suggests the normalization may be invalid). Use only relative amplitude and timing from this trace): (a) linear acceleration: (α) angular acceleration; (θ) angle.




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