Journal of biomechanics
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Journal of biomechanics · Apr 2016
Stumbling reactions during perturbed walking: Neuromuscular reflex activity and 3-D kinematics of the trunk - A pilot study.
Reflex activity of the lower leg muscles involved when compensating for falls has already been thoroughly investigated. However, the trunk׳s role in this compensation strategy remains unclear. The purpose of this study, therefore, was to analyze the kinematics and muscle activity of the trunk during perturbed walking. ⋯ EMG activity of the trunk was increased during stumbling (abdominal: 665 ± 283%; back: 501 ± 215%), without significant differences between muscles. Provoked stumbling leads to a measurable effect on the trunk, quantifiable by an increase in ROM and EMG activity, compared to normal walking. Greater abdominal muscle activity and ROM of lateral flexion may indicate a specific compensation pattern occurring during stumbling.
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Journal of biomechanics · Apr 2016
The poro-elastic behaviour of the intervertebral disc: A new perspective on diurnal fluid flow.
Diurnal disc height changes, due to fluid in- and outflow, are in equilibrium while daytime spinal loading is twice as long as night time rest. A direction-dependent permeability of the endplates, favouring inflow over outflow, reportedly explains this; however, fluid flow through the annulus fibrosus should be considered. This study investigates the fluid flow of entire intervertebral discs. ⋯ When comparing in- and outflow phases, there was no difference in creep, and time-constants were similar indicating no direction-dependent resistance to fluid flow in the entire intervertebral disc. Results provoked a new hypothesis for diurnal fluid flow: in vitro time-constants for loading are shorter than for unloading and in vivo daytime loading is twice as long as night time unloading, i.e. in diurnal loading the intervertebral disc is closer to loading equilibrium than to unloading equilibrium. Per definition, fluid flow is slower close to equilibrium than far from equilibrium; therefore, as diurnal loading occurs closer to loading equilibrium, fluid inflow during night time unloading can balance fluid outflow during daytime loading, despite a longer time-constant.
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Journal of biomechanics · Feb 2016
Biomechanical properties of lumbar endplates and their correlation with MRI findings of lumbar degeneration.
How stiffness and strength of the human lumbar endplate vary with location, spinal level, and its correlation with MRI findings of lumbar degeneration, has not been reported in detail. 27 lumbar spines (16 male, 11 female, 31-49yrs) were harvested from cadavers without history of lumbar lesion or trauma. Disc and endplate degeneration was evaluated from MRI. Micro-CT was used to evaluate endplate microstructure. ⋯ We conclude that endplate properties reflect compressive stresses within adjacent intervertebral discs. Weaker and softer endplates may indicate reduced mechanical loading in decompressed discs that are stress-shielded by the neural arch. Preoperative MRI evaluation of endplate integrity could reduce the risk of implant subsidence following inter-body fusion.
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Journal of biomechanics · Jan 2016
Mechanical testing and non-linear viscoelastic modelling of the human placenta in normal and growth restricted pregnancies.
Intrauterine Growth Restriction (IUGR) is a disease where the placenta is unable to transfer enough nutrients to the fetus, limiting its growth, and resulting in high mortality and life-long morbidities. Current detection rates of IUGR are poor, resulting in limited disease management. Elastography is a promising non-invasive tool for the detection of IUGR, and works by detecting changes in the mechanical properties of the placenta. To date, however, it is not known whether IUGR placentas have different mechanical properties from normal ones, and thus investigating this is the first focus of the current study. The second focus is to evaluate and model the viscoelastic properties of the normal and IUGR placenta, so that it may be possible to improve elastography in the future by incorporating viscoelasticity. ⋯ Our results demonstrate that IUGR placentae have different mechanical properties from normal placentae, and a five parameter bi-exponential NVS model can effectively describe the mechanical properties of the placenta in health and disease.
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Journal of biomechanics · Dec 2015
A machine learning approach to estimate Minimum Toe Clearance using Inertial Measurement Units.
Falls are the primary cause of accidental injuries (52%) and one of the leading causes of death in individuals aged 65 and above. More than 50% of falls in healthy older adults are due to tripping while walking. Minimum toe clearance (i.e., minimum height of the toe above the ground during the mid-swing phase - MTC) has been investigated as an indicator of tripping risk. ⋯ The GRNN based MTC height predictions demonstrated root-mean-square-error (RMSE) of 6.6mm with 9 optimum features for young adults and 7.1mm RMSE with 5 features for the older adults during treadmill walking. The GRNN based MTC height estimation method devised in this project represents approximately 68% less RMSE than other estimation techniques. The research findings show a strong potential for gait monitoring outside the laboratory to provide real-time MTC height information during everyday locomotion.