Institute For Biomedical Engineering (IBE)

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Browsing Institute For Biomedical Engineering (IBE) by Author "Bergh, Oloff Charles Wessel"

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    The Influence of neck muscle characteristics on head kinematics during lateral impacts : a simulation based analysis
    (2023-03) Bergh, Oloff Charles Wessel; Van der Merwe, Johan; De Jongh, Cornel; Derman, Wayne; Stellenbosch University. Faculty of Engineering. Institute of Biomedical Engineering.
    ENGLISH SUMMARY: The skull contains the most critical component of the human body, the brain. Large changes in the velocity and acceleration of the skull, specifically in an angular manner, have been associated with an increased risk of concussion or mild traumatic brain injuries. Modifiable risk factors can be defined as intrinsic characteristics that can be altered to decrease the risk of head injury. Previous studies have investigated neck muscle strength as a potential modifiable risk factor in sports research. However, literature appears to be divided regarding the influence of neck muscle strength on head kinematics and injury risk. Additionally, research associated with individuals who demonstrate a decline in neck muscle strength compared to control subjects appears to be scarce, potentially due to ethical concerns. This project aims to contribute to current literature and evaluate the influence of neck muscle characteristics, such as the maximum isometric and eccentric strength, on the kinematics of the skull during laterally induced head collisions through a simulation-based approach. Multibody dynamic computer models were used to determine the influence of neck muscle characteristics on head kinematics and subsequent head injury risks. The models were based on the original Hyoid model in OpenSim by Mortensen, Vasavada and Merryweather (2018), which has been verified and validated against experimental responses with similar total neck muscle strength values. The Normal model in this project demonstrated the same muscle characteristics as the original Hyoid model. The two stronger models, referred to as the Intermediate and Max models, have increases in maximum isometric and eccentric muscle strength compared to the Normal model. The Intermediate model has realistic achievable neck muscle characteristics of an individual who has undergone specific neck training, while the Max model represents a highly trained athlete with significantly strengthened neck musculature. The Decreased model has lower total neck muscle strength compared to the Normal model and is based on the reductions in muscle characteristics of elderly individuals. The static optimization tool within the OpenSim environment was used to determine the optimal muscular activations of the different models. These activations were subsequently used in the forward dynamic tool to determine the influence of the neck muscle characteristics on head kinematics during increasing lateral impacts. The head kinematics were then used to calculate the head injury criterion (HIC15), a commonly used metric to determine the extent of head injuries based on empirical data. The stronger models consistently showed lower head kinematic and HIC15 values compared to the Normal model, while the Decreased model always demonstrated higher kinematics with a greater risk of injury. At a low external force there was a considerable influence of the neck muscle characteristics on head kinematics and injury risk. However, a non-linear trend indicated that the influence of the neck muscles declined as the external force increased. This could indicate that the influence of the neck muscle characteristics might be overshadowed by large external forces, but could still play a role in reducing head kinematics and injury-risk at lower forces.