Papers by Keyword: Biomechanics

Abstract: The purposes of this study were to explore the biomechanical variations of vertical jump performance in well-trained young group before and after passive static stretching (PSS) of knee flexors muscles and to further discuss how the passive static stretching (PSS) influences vertical jump performance in order to provide a more effective warm-up routine and theoretical basis for physical education (PE) teachers and coaches. 15 male middle school students without any injury histories on lower limbs in the past 3 months were included in this study. Subjects with markers on the lower limbs performed vertical jump performance before and immediately after PSS of knee flexors muscles, respectively. A Vicon motion capture system was used to collect the kinematic data of lower limb and Kistler force platform simultaneously recorded the ground reaction force (GRF) during vertical jump. Significant differences were also found in the kinematics part. In sagittal plane, the hip, knee and ankle highest flexion angles were greater after PSS when take-off (hip: p< 0.05; knee: p< 0.01; ankle: p< 0.05); while the hip and knee highest flexion angles were greater before PSS when landing (hip: p< 0.01; knee: p< 0.05). These results showed that the increased range of motion (ROM) of hip, knee, and ankle because of PSS could boost the explosive extension of lower limb during take-off, which can potentially improve vertical jump performance, although the peak value of GRF after PSS was lower. Therefore, the PSS applied only on knee flexors muscles may have an acute effect on enhancing the vertical jump performance for well-trained young group and should be added to warm-up exercises in middle school sports class and sports training.

Abstract: In this paper an experimental research was performed in case of a human complex motion. The research aim was to evaluate the joint trajectories and angular variations of a human upper limb. Thus an experimental motion analysis was performed, by using a modern equipment called VICON Equipment and the interest joints are: shoulder, elbow and wrist. The experimental activity was developed on a human subject when perform a complex motion from baseball sport. The obtained results will be useful for the temporal recovery of the athletes’ complex motions after a severe injury or to reshape the upper arm behavior when strikes the ball in case of baseball athletes.

Abstract: Manufacturing of medical implants constitutes always a challenge, regarding the constraints involved for these applications, e.g. need for suitable materials or appropriate dimensional tolerances. The aforementioned pose also challenges for the machining process itself, regarding the appropriate machining conditions and machine tool setup and so it is considered as a subject of interest. In the present work, the manufacturing process for knee implants, especially for the femoral component of this type of implants, is discussed, encompassing all the stages from design and planning of each step of the process up to actual machining of the implant component. Finally, the surface quality of the implant after finishing process is assessed for each of the three different finishing processes applied, in order to determine the suitable machining parameters required.

Abstract: This paper presents results of the investigation of two biological role models, the shield bug (Graphosoma italicum) and the carnivorous Waterwheel plant (Aldrovanda vesiculosa). The aim was to identify biological construction and movement principles as inspiration for technical, deployable systems. The subsequent processes of abstraction and simulation of the movement and the design principles are summarized, followed by results on the mechanical investigations on various combinations of fibers and matrices with regard to taking advantage of the anisotropy of fiber-reinforced plastics (FRPs). With the results gained, it was possible to implement defined flexible bending zones in stiff composite components using one composite material, and thereby to mimic the biological role models. First small-scale demonstrators for adaptive façade shading systems – Flectofold and Flexagon – are proving the functionality.

Abstract: There are a few years, it has become the use of artificial discs and effectively to compensate for damaged discs in humans due to the eccentric load applied on the spine. As we know very well that the success of a disc implantation depends strongly on the initial stability of the implant and the integration of the bone tissue of the vertebrae with these discs in the long term. Due to the optimal distribution of mechanical stresses in the surrounding bone. It is for this reason that the search for reasonable solutions to compensate the damaged disk and reduce the stresses in the cortical bone and spongy has become a very important research axis. Several alternatives have been studied, including implant design, prosthesis geometry, prosthetic components and biomaterials used. In this regard, we have proposed two new models for some innovative artificial disks by some of the biomechanics researchers and we have installed these discs between the two vertebrae L5 and S1 of the spine, to ensure spinal stability and avoid slipping, we installed a posterior attachment system (6 screws plus 2 rods) at the pedicular levels of the lumbar vertebra (S1-L5, L5-L4).It is for this technique that we have used finite elements in three dimensions and using the software ANSYS to know the extent of the realization of these discs under the influence of the load applied to them. The numerical results show that these disks played a very important role in the absorption of the stresses and to minimize, On the other hand, the lumbar inter-somatic cage (Model II) filled with cancellous bone is too great a role in reducing the stress compared to another synthetic (Model I) disc. In general, the new model of the inter-somatic cage filled with cancellous bone and reinforced by a posterior fixation system has given a lower level of stress in the cortical bone and the spongy bone of the lumbar vertebra (L5) compared to the healthy disk (D1).

Abstract: Stable osseointegration between implant threads and the surrounding marginal bone provides the mechanical base of an implant for daily chewing activity. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. In this work we numerically analyze by the finite element method the distribution of the equivalent stress and their level in the bone the most fragile element of the dental prosthesis. Each set of the model contained a crown, framework, abutment, implant and bone, subjected to variable dynamic loading according to time.

Abstract: The purpose of this study was to explore the balance of different condition of grounds through changing the inclines, and investigate the influence of lower extremities in different inclines. 20 healthy young males were taken as experimental participants. The Six-degree-of-freedom Motion Platform was taken to change the inclines to: -5°,0°,5°,10°. The Vicon three-dimension motion analysis system was utilized to capture the spatiotemporal parameters and the three-dimensional coordinates of lower extremities. On uphill, incline had no significant impact on balance. But tortuosity of hip and knee could significantly increase with the incline. On downhill, balance was significantly less than flat. Tortuosity of knee joint was significant larger than it on the flat ground. The mobility of hip and knee joint was large on uphill; the mobility of knee is large on downhill, but the balance was reduced. These could provide useful biomechanics information on clinical evaluation with dynamic balance. The result might have great significance to the lower extremities rehabilitation.

Abstract: We analyzed histological data statistically describing the distribution of orientations of vascular smooth muscle cells (VSMC) within porcine aorta. The data were correlated with the fractions of actin, desmin, vimentin, elastin and collagen within the same samples. In samples with more contractile VSMC and less elastin, the symmetrical helices of VSMC were arranged closely to each other and they were more concentrated than in samples with fewer actin-and desmin-positive VSMC and more elastin. The findings are suitable for microstructurally-motivated biomechanical modeling of porcine aorta under normal conditions.

Abstract: Investigation of biomechanical properties of the rabbit bone tissue from a corner of the lower jaw was done. Experimental osteoporosis was induced by ovariectomy and following injections of methylprednisolone. The defects in the greater trochanter region was created and filled with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or HAP/TCP 30/70 together with 5% strontium ranelate. After 3 month animals were euthanased, squared samples have been cut out from a corner of the lower jaw and tested on a bend. Results of research show, that the corner of a lower jaw in rabbit becomes more rigid after filling of defects in the greater trochanter region with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or granules together with strontium ranelate. The ultimate strain for the bone tissue in the 2^nd and 3^rd group is less, than for control group. Thus, local uses calcium – phosphatic bioceramic material around the greater trochanter region improves biomechanical parameters of a bone tissue in the lower jaw of animals.

Abstract: The precision in localization of the UBISENSE Real Time Location System was assessed for evaluating the possibility of using the system in the detection of movements and position of athletes on the field during sport performance. The system was implemented in an indoor lab space measuring 11 by 7 meters. Four sensors were installed on the roof at a height of 3 meters above floor. Various sampling rates were used with a single location tag. UBISENSE is using UWB localization technology based on the triangulation of time of arrivals of UWB pulses at the different antenna sensors. Precision varied in position and speed determination being position resolution in the range of 15 to 50 cm while speed precision was in the figure of 6% at slow actual speed of 0.18 m/s up to 20% at fast speed of 1 m/s. This was mainly due to sampling frequency in the location system. In conclusion, as long as speed of the athlete is not at stake, the position can be measured with quite good resolution and sampling frequency so to permit the evaluation of sport performances of the athlete during the exercise or activity. A very attractive feature of the system is that the athlete must be tagged with a very low-weight and quite comfortable active tag which, on the contrary to video tracking systems, doesn’t need to remain in the field of view.