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Designing for Head and Neck Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Lateral flexion, or side-bending of the head and neck toward the shoulder, occurs in a coronal (frontal) plane (Figure 3.16, lower). The C2-3 to C7-T1 segments again provide much of the motion, about 40 degrees. Motion at the sub-occipital (skull-C1, C1-C2) segment adds about 8 degrees. The specific contours of the lower cervical vertebrae always add a degree of rotation to lateral flexion of the neck (Palastanga et al., 2002, p. 521). Although different authors credit different combinations of muscles with this movement, the sternocleidomastoid, splenius capitis, and trapezius muscles all likely supply major forces for this motion (Figure 3.16, upper), as well as for the return to an upright head and neck position (Kendall, McCreary, Provance, Rodgers, & Romani, 2005, pp. 148–149, Palastanga et al., 2002, p. 489). The R sternocleidomastoid and upper trapezius contract together, as agonists, in a shortening contraction, along with the R splenius capitis, to tip the R ear toward the R shoulder. The same muscles, on the L, control the motion with lengthening contractions and act as antagonists. The splenius capitis lends an element of neck extension when it laterally flexes the head on the neck (Teton Data Systems, & Primal Pictures Ltd., 2014, Head & Neck). To return the head to upright, the muscle actions reverse.
Repeatability of electromyography normalization of the neck and shoulder muscles in symptomatic office workers
Published in International Journal of Occupational Safety and Ergonomics, 2018
Montakarn Chaikumarn, Nuttika Nakphet, Prawit Janwantanakul
In this study, we used SEMG because it was practical to obtain the signal during VDU work. However, SEMG has limitations in the assessment of superficial muscles [43]. There were differences in the biomechanical models corresponding to the muscle and electrode sites [21,27]. Sommerich et al. [24] indicated that a surface electrode located at the C4/5 level could access the semispinalis capitis, splenius capitis and trapezius. However, they reported that the trapezius did not contribute to head or neck motion or stabilization at that site (C4/5). Therefore, in this study we chose to place the surface electrodes at the C4/5 level for the cervical erector spinae under the assumption that the same neck muscle group could perform a similar function to neck extension. Further study is needed to address this issue and could replicate this study in other deep muscles via an invasive technique.
Cervical spine joint loading with neck flexion
Published in Ergonomics, 2020
Jeff Matthew Barrett, Colin McKinnon, Jack P. Callaghan
Surface electromyography (EMG) electrodes were used to collect the level of muscular activation from 10 muscles (5 bilaterally): splenius capitis, sternocleidomastoid, levator scapulae, the cervical erectors, and the upper trapezius. A 16-channel Noraxon Telemyo 2400 T G2 Telemetry EMG system (Noraxon USA Inc., Scottsdale, AZ) was used to amplify the EMG signal, which was then collected at 1500 Hz using a 16-bit analog-to-digital card. The resulting raw EMG signal was detrended, full-wave rectified and low-passed filtered with a single-pass critically damped filter with cut-off frequencies chosen to mimic the electromechanical delay of each specified muscle. Each channel of EMG was normalised to the maximum of the maximal voluntary exertion trials.
Evaluation of vertical and multi-axial suspension seats for reducing vertical-dominant and multi-axial whole body vibration and associated neck and low back joint torque and muscle activity
Published in Ergonomics, 2022
Kiana Kia, Harold T. Bae, Peter W. Johnson, Jack T. Dennerlein, Jeong Ho Kim
Muscle activity was bilaterally collected at 1,000 Hz from splenius capitis (SPL—neck muscle), sternocleidomastoid (SCM—neck muscle), trapezius (TRAP—neck/shoulder muscle), and erector spinae (ES—low back muscle) using 8-channel electromyography (EMG) data logger with a hardware pre-amplifier bandpass filter of 15–500 Hz (ME6000; Mega Electronics; Kuopio, Finland) and Ag/AgCl surface electrodes (N-00-S/25; Ambu; Ballerup, Denmark). Skin preparation, muscle identification, and electrode placement were conducted in accordance with the European recommendation for surface electromyography (Hermens et al. 1999). The electrode sites were marked with permanent markers for the consistent electrode placements across the experimental sessions.