Mechanical Engineering - Research Publications

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    Effects of Prophylactic Knee Bracing on Lower Limb Kinematics, Kinetics, and Energetics During Double-Leg Drop Landing at 2 Heights
    Ewing, KA ; Begg, RK ; Galea, MP ; Lee, PVS (SAGE PUBLICATIONS INC, 2016-07)
    BACKGROUND: Anterior cruciate ligament (ACL) injuries commonly occur during landing maneuvers. Prophylactic knee braces were introduced to reduce the risk of ACL injuries, but their effectiveness is debated. HYPOTHESES: We hypothesized that bracing would improve biomechanical factors previously related to the risk of ACL injuries, such as increased hip and knee flexion angles at initial contact and at peak vertical ground-reaction force (GRF), increased ankle plantar flexion angles at initial contact, decreased peak GRFs, and decreased peak knee extension moment. We also hypothesized that bracing would increase the negative power and work of the hip joint and would decrease the negative power and work of the knee and ankle joints. STUDY DESIGN: Controlled laboratory study. METHODS: Three-dimensional motion and force plate data were collected from 8 female and 7 male recreational athletes performing double-leg drop landings from 0.30 m and 0.60 m with and without a prophylactic knee brace. GRFs, joint angles, moments, power, and work were calculated for each athlete with and without a knee brace. RESULTS: Prophylactic knee bracing increased the hip flexion angle at peak GRF by 5.56° (P < .001), knee flexion angle at peak GRF by 4.75° (P = .001), and peak hip extension moment by 0.44 N·m/kg (P < .001). Bracing also increased the peak hip negative power by 4.89 W/kg (P = .002) and hip negative work by 0.14 J/kg (P = .001) but did not result in significant differences in the energetics of the knee and ankle. No differences in peak GRFs and peak knee extension moment were observed with bracing. CONCLUSION: The application of a prophylactic knee brace resulted in improvements in important biomechanical factors associated with the risk of ACL injuries. CLINICAL RELEVANCE: Prophylactic knee braces may help reduce the risk of noncontact knee injuries in recreational and professional athletes while playing sports. Further studies should investigate different types of prophylactic knee braces in conjunction with existing training interventions so that the sports medicine community can better assess the effectiveness of prophylactic knee bracing.
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    Prophylactic knee bracing alters lower-limb muscle forces during a double-leg drop landing
    Ewing, KA ; Fernandez, JW ; Begg, RK ; Galea, MP ; Lee, PVS (ELSEVIER SCI LTD, 2016-10-03)
    Anterior cruciate ligament (ACL) injury can be a painful, debilitating and costly consequence of participating in sporting activities. Prophylactic knee bracing aims to reduce the number and severity of ACL injury, which commonly occurs during landing maneuvers and is more prevalent in female athletes, but a consensus on the effectiveness of prophylactic knee braces has not been established. The lower-limb muscles are believed to play an important role in stabilizing the knee joint. The purpose of this study was to investigate the changes in lower-limb muscle function with prophylactic knee bracing in male and female athletes during landing. Fifteen recreational athletes performed double-leg drop landing tasks from 0.30m and 0.60m with and without a prophylactic knee brace. Motion analysis data were used to create subject-specific musculoskeletal models in OpenSim. Static optimization was performed to calculate the lower-limb muscle forces. A linear mixed model determined that the hamstrings and vasti muscles produced significantly greater flexion and extension torques, respectively, and greater peak muscle forces with bracing. No differences in the timings of peak muscle forces were observed. These findings suggest that prophylactic knee bracing may help to provide stability to the knee joint by increasing the active stiffness of the hamstrings and vasti muscles later in the landing phase rather than by altering the timing of muscle forces. Further studies are necessary to quantify whether prophylactic knee bracing can reduce the load placed on the ACL during intense dynamic movements.
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    Modelling apical columnar epithelium mechanics from circumferential contractile fibres
    Boyd, ARB ; Moore, S ; Sader, JE ; Lee, PVS (SPRINGER HEIDELBERG, 2017-10)
    Simple columnar epithelia are formed by individual epithelial cells connecting together to form single cell high sheets. They are a main component of many important body tissues and are heavily involved in both normal and cancerous cell activities. Prior experimental observations have identified a series of contractile fibres around the circumference of a cross section located in the upper (apical) region of each cell. While other potential mechanisms have been identified in both the experimental and theoretical literature, these circumferential fibres are considered to be the most likely mechanism controlling movement of this cross section. Here, we investigated the impact of circumferential contractile fibres on movement of the cross section by creating an alternate model where movement is driven from circumferential contractile fibres, without any other potential mechanisms. In this model, we utilised a circumferential contractile fibre representation based on investigations into the movement of contractile fibres as an individual system, treated circumferential fibres as a series of units, and matched our model simulation to experimental geometries. By testing against laser ablation datasets sourced from existing literature, we found that circumferential fibres can reproduce the majority of cross-sectional movements. We also investigated model predictions related to various aspects of cross-sectional movement, providing insights into epithelium mechanics and demonstrating the usefulness of our modelling approach.
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    Three-dimensional modelling of auxetic sandwich panels for localised impact resistance
    Imbalzano, G ; Tran, P ; Ngo, TD ; Lee, PVS (Sage Publications, 2017)
    Sandwich panels with auxetic lattice cores confined between metallic facets are proposed for localised impact resistance applications. Their performance under localised impact is numerically studied, considering the rate-dependent effects. The behaviour of the composite structure material at high strain rates is modelled with the Johnson-Cook model. Parametric analyses are conducted to assess the performance of different designs of the hybrid composite structures. The results are compared with monolithic panels of equivalent areal mass and material in terms of deformations and plastic energy dissipation. Design parameters considered for the parametric analyses include the auxetic unit cell effective Poisson’s ratio, thickness of the facet, material properties and radius of the unit cell’s struts. Significant reduction in computational time is achieved by modelling a quarter of the panel, with shell elements for facets and beam elements for the auxetic core. With projectile impacts up to 200 m/s, the auxetic composite panels are found to be able to absorb a similar amount of energy through plastic deformation, while the maximum back facet displacements are reduced up to 56% due to localised densification and plastic deformation of the auxetic core.
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    Cellular Biomechanics in Drug Screening and Evaluation: Mechanopharmacology
    Krishnan, R ; Park, J-A ; Seow, CY ; Lee, PV-S ; Stewart, AG (ELSEVIER SCIENCE LONDON, 2016-02)
    The study of mechanobiology is now widespread. The impact of cell and tissue mechanics on cellular responses is well appreciated. However, knowledge of the impact of cell and tissue mechanics on pharmacological responsiveness, and its application to drug screening and mechanistic investigations, have been very limited in scope. We emphasize the need for a heightened awareness of the important bidirectional influence of drugs and biomechanics in all living systems. We propose that the term 'mechanopharmacology' be applied to approaches that employ in vitro systems, biomechanically appropriate to the relevant (patho)physiology, to identify new drugs and drug targets. This article describes the models and techniques that are being developed to transform drug screening and evaluation, ranging from a 2D environment to the dynamic 3D environment of the target expressed in the disease of interest.
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    Muscle coordination during single-leg landing: Implications for ACL injuries
    Mokhtarzadeh, H ; Correa, T ; Hua Yeow, C ; Cho Hong Goh, J ; Oetomo, D ; Lee, P (Orthopaedic Research Society, 2012)