Universität Stuttgart

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Institute: search.filters.UBSInstitut.Institut für Technische InformatikAuthor: search.filters.author.Siebert, Tobias

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    A muscle model for injury simulation
    (2023) Millard, Matthew; Kempter, Fabian; Fehr, Jörg; Stutzig, Norman; Siebert, Tobias
    Car accidents frequently cause neck injuries that are painful, expensive, and difficult to simulate. The movements that lead to neck injury include phases in which the neck muscles are actively lengthened. Actively lengthened muscle can develop large forces that greatly exceed the maximum isometric force. Although Hill-type models are often used to simulate human movement, this model has no mechanism to develop large tensions during active lengthening. When used to simulate neck injury, a Hill model will underestimate the risk of injury to the muscles but may overestimate the risk of injury to the structures that the muscles protect. We have developed a musculotendon model that includes the viscoelasticity of attached crossbridges and has an active titin element. In this work we evaluate the proposed model to a Hill model by simulating the experiments of Leonard et al. [1] that feature extreme active lengthening.
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    Cervical muscle reflexes during lateral accelerations
    (2023) Millard, Matthew; Hunger, Susanne; Broß, Lisa; Fehr, Jörg; Holzapfel, Christian; Stutzig, Norman; Siebert, Tobias
    Autonomous vehicles will allow a variety of seating orientations that may change the risk of neck injury during an accident. Having a rotated head at the time of a rear-end collision in a conventional vehicle is associated with a higher risk of acute and chronic whiplash. The change in posture affects both the movement of the head and the response of the muscles. We are studying the reflexes of the muscles of the neck so that we can validate the responses of digital human body models that are used in crash simulations. The neck movements and muscle activity of 21 participants (11 female) were recorded at the Stuttgart FKFS mechanical driving simulator. During the maneuver we recorded the acceleration of the seat and electromyographic (EMG) signals from the sternocleidomastoid (STR) muscles using a Biopac MP 160 system (USA). As intuition would suggest, the reflexes of the muscles of the neck are sensitive to posture and the direction of the acceleration.
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    Whiplash simulation: how muscle modelling and movement interact
    (2022) Millard, Matthew; Siebert, Tobias; Stutzig, Norman; Fehr, Jörg
    Whiplash injury and associated disorders are costly to society and individuals. Accurate simulations of neck movement during car accidents are needed to assess the risk of whiplash injury. Existing simulations indicate that Hill-type muscle models are too compliant, and as a result, predict more neck movement than is observed during in-vivo experiments. Simulating head and neck movement is challenging because many of the neck muscles operate on the descending limb of the force-length curve, a region that Hill-type models inaccurately capture. Hill-type muscle models have negative stiffness on the descending limb of the force-length curve and so develop less force the more they are lengthened. Biological muscle, in contrast, can develop large transient forces during active lengthening and sustain large forces when aggressively lengthened. Recently, a muscle model has been developed that mimics the active impedance of muscle in the short range and can capture the large forces generated during extreme lengthening. In this work, we will compare the accuracy of simulated neck movements, using both a Hill-type model and the model of Millard et al., to the in-vivo neck movement. If successful, the improved accuracy of our simulations will make it possible to predict and help prevent neck injury.