Journal of biomechanics
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Journal of biomechanics · Jun 2018
Spatiotemporal and kinematic changes in gait while carrying an energy harvesting assault pack system.
Soldiers are fielded with a variety of equipment including battery powered electronic devices. An energy harvesting assault pack (EHAP) was developed to provide a power source to recharge batteries and reduce the quantity and load of extra batteries carried into the field. Little is known about the biomechanical implications of carrying a suspended-load energy harvesting system compared to the military standard assault pack (AP). ⋯ When carrying the EHAP, strides (decline: p = 0.007) and double support stance time (incline: p = 0.006) was longer, the knee was more flexed at heel strike (level: p = 0.014; incline: p < 0.001) and there was a smaller change in knee flexion during weight acceptance (decline: p = 0.0013; level: p = 0.007; incline: p = 0.0014). Carrying the EHAP elicits changes to gait biomechanics compared to carrying the standard AP. Understanding how load-suspension systems influence loaded gait biomechanics are warranted before transitioning these systems into military or recreational environments.
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Journal of biomechanics · Apr 2018
Flow instability detected in ruptured versus unruptured cerebral aneurysms at the internal carotid artery.
Flow instability has emerged as a new hemodynamic metric hypothesized to have potential value in assessing the rupture risk of cerebral aneurysms. However, diverse findings have been reported in the literature. In the present study, high-resolution hemodynamic simulations were performed retrospectively on 35 aneurysms (10 ruptured & 25 unruptured) located at the internal carotid artery (ICA). ⋯ In contrast, low wall shear stress area (LSA) and pressure loss coefficient (PLC) exhibited significant correlations with the status of aneurysm rupture. In conclusion, the present study suggests that the presence of flow instability may not correlate closely with the status of aneurysm rupture, at least for ICA aneurysms. On the other hand, the retrospective nature of the study and the small sample size may have to some extent compromised the reliability of the conclusion, and therefore large-scale prospective studies would be needed to further address the issue.
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Journal of biomechanics · Apr 2018
Structural modeling reveals microstructure-strength relationship for human ascending thoracic aorta.
High lethality of aortic dissection necessitates accurate predictive metrics for dissection risk assessment. The not infrequent incidence of dissection at aortic diameters <5.5 cm, the current threshold guideline for surgical intervention (Nishimura et al., 2014), indicates an unmet need for improved evidence-based risk stratification metrics. Meeting this need requires a fundamental understanding of the structural mechanisms responsible for dissection evolution within the vessel wall. ⋯ Multiphoton imaging derived collagen fiber organization for each patient cohort was explicitly incorporated in our model. Model parameters were calibrated using experimentally-measured uniaxial tensile strength data in the circumferential direction for each cohort, while the model was validated by contrasting simulated tissue strength against experimentally-measured strength in the longitudinal direction. Orientation distribution, controlling the fraction of loaded collagen fibers at a given stretch, was identified as a key feature governing anisotropic tissue strength for all patient cohorts.
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Journal of biomechanics · Apr 2018
Trunk and lower limb coordination during lifting in people with and without chronic low back pain.
Differences in synchronous movement between the trunk and lower limb during lifting have been reported in chronic low back pain (CLBP) patients compared to healthy people. However, the relationship between movement coordination and disability in CLBP patients has not been investigated. A cross-sectional study was conducted to compare regional lumbar and lower limb coordination between CLBP (n = 43) and control (n = 29) groups. ⋯ There were no significant differences in lumbar-hip and hip-knee MARP and DP between the lower-disability CLBP and control groups. Lumbar-hip MARP was positively associated with ODI (R2 = 0.092, β = 0.30, p = 0.048). High-disability CLBP patients demonstrated decreased lumbar-hip movement coordination and stiffer hip-knee movement during lifting than low-disability CLBP patients and healthy controls.
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Journal of biomechanics · Apr 2018
Kinematics of lower limbs during walking are emulated by springy walking model with a compliantly connected, off-centered curvy foot.
The dynamics of the center of mass (CoM) during walking and running at various gait conditions are well described by the mechanics of a simple passive spring loaded inverted pendulum (SLIP). Due to its simplicity, however, the current form of the SLIP model is limited at providing any further information about multi-segmental lower limbs that generate oscillatory CoM behaviors and their corresponding ground reaction forces. Considering that the dynamics of the CoM are simply achieved by mass-spring mechanics, we wondered whether any of the multi-joint motions could be demonstrated by simple mechanics. ⋯ From the mechanically simulated trajectories of the ankle joint and CoM, the motion of lower-limb segments, such as thigh and shank angles, could be estimated from inverse kinematics. The estimation of lower limb kinematics showed a qualitative match with empirical data of walking at various speeds. The representability of passive compliant mechanics for the kinetics of the CoM and ankle joint and lower limb joint kinematics implies that the coordination of multi-joint lower limbs during gait can be understood with a mechanical framework.