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- Fice, Jason, 1985, et al.
(författare)
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Neck Muscle and Head/Neck Kinematic Responses While Bracing Against the Steering Wheel During Front and Rear Impacts
- 2021
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Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 49:3, s. 1069-1082
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Tidskriftsartikel (refereegranskat)abstract
- Drivers often react to an impending collision by bracing against the steering wheel. The goal of the present study was to quantify the effect of bracing on neck muscle activity and head/torso kinematics during low-speed front and rear impacts. Eleven seated subjects (3F, 8 M) experienced multiple sled impacts (Delta v = 0.77 m/s; a(peak) = 19.9 m/s(2), Delta t = 65.5 ms) with their hands on the steering wheel in two conditions: relaxed and braced against the steering wheel. Electromyographic activity in eight neck muscles (sternohyoid, sternocleidomastoid, splenius capitis, semispinalis capitis, semispinalis cervicis, multifidus, levator scapulae, and trapezius) was recorded unilaterally with indwelling electrodes and normalized by maximum voluntary contraction (MVC) levels. Head and torso kinematics (linear acceleration, angular velocity, angular rotation, and retraction) were measured with sensors and motion tracking. Muscle and kinematic variables were compared between the relaxed and braced conditions using linear mixed models. We found that pre-impact bracing generated only small increases in the pre-impact muscle activity (< 5% MVC) when compared to the relaxed condition. Pre-impact bracing did not increase peak neck muscle responses during the impacts; instead it reduced peak trapezius and multifidus muscle activity by about half during front impacts. Bracing led to widespread changes in the peak amplitude and timing of the torso and head kinematics that were not consistent with a simple stiffening of the head/neck/torso system. Instead pre-impact bracing served to couple the torso more rigidly to the seat while not necessarily coupling the head more rigidly to the torso.
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- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
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Cervical Muscle Responses to Multi-Directional Perturbations
- 2014
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Ingår i: 7th World Congress of Biomechanics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Numerical human models are widely used in the design process and evaluation of passive and active vehicle safety systems in pre-crash and crash situations. Development and validation of human models that simulate neuromuscular control requires information on muscle activation patterns and contraction levels for different loading directions. Due to the lack of experimental data on cervical muscle recruitment strategies, the aim of this study was to provide activation patterns for superficial and deep cervical muscles during multidirectional perturbations.Eight volunteers received three perturbations (apeak=1.5g, ∆v=0.5m/s) in each of eight different directions while seated unrestrained on a sled-mounted car seat without a head restraint. Volunteers received no warning of perturbation onset. Electromyographic (EMG) activity was measured with wire electrodes inserted into the left sternocleidomastoid (SCM), trapezius (Trap), levator scapulae (LS), splenius capitis (SPL), semispinalis capitis (SCap), semispinalis cervicis (SCerv), and multifidus (Multi) muscles, and with surface electrodes over the sternohyoid (STH) muscle. All EMG signals were normalized with maximum voluntary isometric contraction activity.All median muscle activities were below 5%MVC before perturbation onset. During perturbation, most muscles showed distinctive activation patterns consistent with their anatomical location and function. Anterior muscles (SCM, STH) activated to counteract head extension and posterior muscles, except SPL, activated to counteract flexion (Figure). Although with different levels of contraction, SCap, SCerv, and Multi activated synergistically with the highest activity (89%, 50%, and 36%MVC respectively, 110ms after perturbation onset) during rearward and ipsilateral rearward oblique perturbations. Activation levels were generally five times lower in other directions. Despite its posterior location, SPL had activities between 19%MVC and 27%MVC during forward, forward oblique and lateral perturbations, but
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- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
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Dynamic Spatial Tuning of Cervical Muscle Reflexes to Multidirectional Seated Perturbations
- 2015
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 40:4, s. E211-E219
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Tidskriftsartikel (refereegranskat)abstract
- Study Design. Human volunteers were exposed experimentally to multidirectional seated perturbations.Objective. To determine the activation patterns, spatial distribution and preferred directions of reflexively activated cervical muscles for human model development and validation.Summary of Background Data. Models of the human head and neck are used to predict occupant kinematics and injuries in motor vehicle collisions. Because of a dearth of relevant experimental data, few models use activation schemes based on in vivo recordings of muscle activation and instead assume uniform activation levels for all muscles within presumed agonist or antagonist groups. Data recorded from individual cervical muscles are needed to validate or refute this assumption.Methods. Eight subjects (6 males, 2 females) were exposed to seated perturbations in 8 directions. Electromyography was measured with wire electrodes inserted into the sternocleidomastoid, trapezius, levator scapulae, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles. Surface electrodes were used to measure sternohyoid activity. Muscle activity evoked by the perturbations was normalized with recordings from maximum voluntary contractions.Results. The multidirectional perturbations produced activation patterns that varied with direction within and between muscles. Sternocleidomastoid and sternohyoid activated similarly in forward and forward oblique directions. The semispinalis capitis, semispinalis cervicis, and multifidus exhibited similar spatial patterns and preferred directions, but varied in activation levels. Levator scapulae and trapezius activity generally remained low, and splenius capitis activity varied widely between subjects.Conclusion. All muscles showed muscle- and direction-specific contraction levels. Models should implement muscle- and direction-specific activation schemes during simulations of the head and neck responses to omnidirectional horizontal perturbations where muscle forces influence kinematics, such as during emergency maneuvers and low-severity crashes.Level of Evidence: N/A
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- Olafsdottir, Jóna Marin, 1985, et al.
(författare)
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Trunk muscle recruitment patterns in simulated precrash events
- 2018
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Ingår i: Traffic Injury Prevention. - : Informa UK Limited. - 1538-957X .- 1538-9588. ; 19, s. S186-S188
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To quantify trunk muscle activation levels during whole body accelerations that simulate precrash events in multiple directions and to identify recruitment patterns for the development of active human body models. Methods: Four subjects (1 female, 3 males) were accelerated at 0.55 g (net Δv = 4.0 m/s) in 8 directions while seated on a sled-mounted car seat to simulate a precrash pulse. Electromyographic (EMG) activity in 4 trunk muscles was measured using wire electrodes inserted into the left rectus abdominis, internal oblique, iliocostalis, and multifidus muscles at the L2–L3 level. Muscle activity evoked by the perturbations was normalized by each muscle's isometric maximum voluntary contraction (MVC) activity. Spatial tuning curves were plotted at 150, 300, and 600 ms after acceleration onset. Results: EMG activity remained below 40% MVC for the three time points for most directions. At the 150- and 300 ms time points, the highest EMG amplitudes were observed during perturbations to the left (–90°) and left rearward (–135°). EMG activity diminished by 600 ms for the anterior muscles, but not for the posterior muscles. Conclusions: These preliminary results suggest that trunk muscle activity may be directionally tuned at the acceleration level tested here. Although data from more subjects are needed, these preliminary data support the development of modeled trunk muscle recruitment strategies in active human body models that predict occupant responses in precrash scenarios.
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- Siegmund, Gunter, et al.
(författare)
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Electromyography of Superficial and Deep Neck Muscles During Isometric, Voluntary, and Reflex Contractions
- 2007
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Ingår i: Journal of Biomechanical Engineering. - : ASME. - 0148-0731 .- 1528-8951. ; 129:1, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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