Letteratura scientifica selezionata sul tema "Moments de flexion des vagues"
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Articoli di riviste sul tema "Moments de flexion des vagues"
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Pollard, Jonisha P., William L. Porter e Mark S. Redfern. "Forces and Moments on the Knee During Kneeling and Squatting". Journal of Applied Biomechanics 27, n. 3 (agosto 2011): 233–41. http://dx.doi.org/10.1123/jab.27.3.233.
Testo completoAbstract (sommario):
Euler angle decomposition and inverse dynamics were used to determine the knee angles and net forces and moments applied to the tibia during kneeling and squatting with and without kneepads for 10 subjects in four postures: squatting (Squat), kneeling on the right knee (One Knee), bilateral kneeling near full flexion (Near Full) and bilateral kneeling near 90° flexion (Near 90). Kneepads affected the knee flexion (p= .002), medial forces (p= .035), and internal rotation moments (p= .006). Squat created loading conditions that had higher varus (p< .001) and resultant moments (p= .027) than kneeling. One Knee resulted in the highest force magnitudes and net moments (p< .001) of the kneeling postures. Thigh-calf and heel-gluteus contact forces decreased the flexion moment on average by 48% during Squat and Near Full.
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Gál, J. M. "Mammalian spinal biomechanics. I. Static and dynamic mechanical properties of intact intervertebral joints." Journal of Experimental Biology 174, n. 1 (1 gennaio 1993): 247–80. http://dx.doi.org/10.1242/jeb.174.1.247.
Testo completoAbstract (sommario):
Four-point bending was used to apply pure extension and flexion moments to the ligamentous lumbosacral spine and pelvic girdle of monkey (Macaca fascicularis), rabbit (domestic and wild, Oryctolagus cuniculus), badger (Meles meles), wallaby (Wallabia rufogrisea frutica), sheep (Ovis aries), seal (Phoca vitulina) and tiger (Panthera tigris). The absolute ranges of angular change in lumbar-lumbar joints (from X-radiographs) were considerable and similar in monkey and wallaby (greater in flexion) and in rabbit and badger (symmetrical in extension and flexion). Mass-specific bending comparisons showed that monkey and seal joints were the most and least resistant, respectively, to these moments. The patterns of mobility showed no clear scaling effects. Subsequently, additional ligamentous joint complexes (three vertebrae and two intervertebral discs) of monkey, wallaby, tiger, jaguar (Panthera onca) and seal (Halichoerus grypus) were subjected to cyclic extension and flexion moments. Changes in intervertebral angle (y, from X-radiographs) were modelled as functions of applied specific bending moments (x):y=A(1-e-Bx). A and B values represented bending capacities and joint compliances respectively. Homologous monkey and wallaby joints had considerable flexion capacities, with low compliances. Homologous jaguar and tiger joints had limited flexion capacities, but greater compliances. The data suggest that flexion resistance may be controlled by different mechanisms in different species.
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Dall, P. M., B. Müller, I. Stallard, J. Edwards e M. H. Granat. "The functional use of the reciprocal hip mechanism during gait for paraplegic patients walking in the Louisiana State University reciprocating gait orthosis". Prosthetics and Orthotics International 23, n. 2 (agosto 1999): 152–62. http://dx.doi.org/10.3109/03093649909071627.
Testo completoAbstract (sommario):
Reciprocally linked orthoses used for paraplegic walking have some form of linkage between the two hip joints. It has been assumed that flexion of the swinging leg is driven by extension of the stance leg. The aims of this study were to investigate the moments generated around the hip joint by the two cables in a Louisiana State University Reciprocating Gait Orthosis (LSU-RGO). Six (6) subjects were recruited from the Regional Spinal Injuries Centre at Southport, who were experienced RGO users. The cables were fitted with strain gauged transducers to measure cable tension. Foot switches were used to divide the gait into swing and stance phases. A minimum of 20 steps were analysed for each subject. Moments about the hip joint for each phase of gait were calculated. There were no moments generated by the front cable in 4 of the subjects. In only 2 subjects did the cable generate a moment that could assist hip flexion during the swing phase. These moments were very low and at best could only have made a small contribution to limb flexion. The back cable generated moments that clearly prevented bilateral flexion. It was concluded that the front cable, as used by these experienced RGO users, did not aid flexion of the swinging limb.
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Gillette, Jason C., Catherine A. Stevermer, Stacey A. Meardon, Timothy R. Derrick e Charles V. Schwab. "Upper Extremity and Lower Back Moments during Carrying Tasks in Farm Children". Journal of Applied Biomechanics 25, n. 2 (maggio 2009): 149–55. http://dx.doi.org/10.1123/jab.25.2.149.
Testo completoAbstract (sommario):
Farm youth commonly perform animal care tasks such as feeding and watering. The purpose of this study was to determine the effects of age, bucket size, loading symmetry, and amount of load on upper body moments during carrying tasks. Fifty-four male and female participants in four age groups (8–10 years, 12–14 years, 15–17 years, and adults, 20–26 years) participated in the study. Conditions included combinations of large or small bucket sizes, unilateral or bilateral loading, and load levels of 10% or 20% of body weight (BW). During bucket carrying, elbow flexion, shoulder flexion, shoulder abduction, shoulder external rotation, L5/S1 extension, L5/S1 lateral bending, and L5/S1 axial rotation moments were estimated using video data. The 8–10 year-old group did not display higher proportional joint moments as compared with adults. Decreasing the load from 20% BW to 10% BW significantly decreased maximum normalized elbow flexion, shoulder flexion, shoulder abduction, shoulder external rotation, L5/S1 lateral bending, and L5/S1 axial rotation moments. Carrying the load bilaterally instead of unilaterally also significantly reduced these six maximum normalized joint moments. In addition, modifying the carrying task by using smaller one-gallon buckets produced significant reductions in maximum L5/S1 lateral bending moments.
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Kaur, Mandeep, Daniel Cury Ribeiro, Kate E. Webster e Gisela Sole. "Association Between Knee Moments During Stair Navigation and Participant-Related Factors in Individuals With Anterior Cruciate Ligament Reconstruction: A Cross-Sectional Study". Journal of Sport Rehabilitation 31, n. 2 (1 febbraio 2022): 174–80. http://dx.doi.org/10.1123/jsr.2021-0104.
Testo completoAbstract (sommario):
Context: Altered knee joint mechanics may be related to quadriceps muscle strength, time since surgery, and sex following anterior cruciate ligament reconstruction (ACLR). The aim of this study was to investigate the association between knee moments, with participant-related factors during stair navigation post-ACLR. Design: Cross-sectional study. Methods: A total of 30 participants (14 women) with ACLR, on average 7.0 (SD 4.4) years postsurgery were tested during stair ascent and descent in a gait laboratory. Motion capture was conducted using a floor-embedded force plate and 11 infrared cameras. Quadriceps concentric and eccentric muscle strength was measured with an isokinetic dynamometer at 60°/s, and peak torques recorded. Multiple regression analyses were performed between external knee flexion and adduction moments, respectively, and quadriceps peak torque, sex, and time since ACLR. Results: Higher concentric quadriceps strength and female sex accounted for 55.7% of the total variance for peak knee flexion moment during stair ascent (P < .001). None of the independent variables accounted for variance in knee adduction moment (P = .698). No significant associations were found for knee flexion and adduction moments during for stair descent. Conclusion: Higher quadriceps concentric strength and sex explains major variance in knee flexion moments during stair ascent. The strong association between muscle strength and external knee flexion moments during stair ascent indicate rehabilitation tailored for quadriceps may optimize knee mechanics, particularly for women.
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Andrysek, Jan, Susan Klejman e John Kooy. "Examination of Knee Joint Moments on the Function of Knee-Ankle-Foot Orthoses During Walking". Journal of Applied Biomechanics 29, n. 4 (agosto 2013): 474–80. http://dx.doi.org/10.1123/jab.29.4.474.
Testo completoAbstract (sommario):
The goal of this study was to investigate clinically relevant biomechanical conditions relating to the setup and alignment of knee-ankle-foot orthoses and the influence of these conditions on knee extension moments and orthotic stance control during gait. Knee moments were collected using an instrumented gait laboratory and concurrently a load transducer embedded at the knee-ankle-foot orthosis knee joint of four individuals with poliomyelitis. We found that knee extension moments were not typically produced in late stance-phase of gait. Adding a dorsiflexion stop at the orthotic ankle significantly decreased the knee flexion moments in late stance-phase, while slightly flexing the knee in stance-phase had a variable effect. The findings suggest that where users of orthoses have problems initiating swing-phase flexion with stance control orthoses, an ankle dorsiflexion stop may be used to enhance function. Furthermore, the use of stance control knee joints that lock while under flexion may contribute to more inconsistent unlocking of the stance control orthosis during gait.
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Weir, Gillian, Jacqueline Alderson, Natalie Smailes, Bruce Elliott e Cyril Donnelly. "A Reliable Video-based ACL Injury Screening Tool for Female Team Sport Athletes". International Journal of Sports Medicine 40, n. 03 (10 gennaio 2019): 191–99. http://dx.doi.org/10.1055/a-0756-9659.
Testo completoAbstract (sommario):
AbstractThis study aimed to develop a 2-dimensional (2D) video screening tool capable of predicting an athlete’s peak 3-dimensional (3D) knee moments during unplanned sidestepping. 2D video-based kinematic measures were simultaneously captured with 3D peak knee moments for 30 female field hockey players (15 junior, 15 senior). Intra- and intertester repeatability of 2D kinematic measures was performed. Then, linear regression models were used to model 3D knee moments from 2D kinematic variables utilizing 80% of the sample (n=24). Regression equations were then validated on the remaining 20% of the sample (n=6). Angular 2D measures had good-excellent intra- (ICC=0.936–0.998) and intertester (ICC=0.662–0.949) reliability. Displacement measures had poor-excellent intra- (ICC=0.377–0.539) and inter-tester (ICC=0.219–0.869) reliability. Significant independent predictors of peak knee moments were dynamic knee valgus, knee flexion angle at foot strike, trunk flexion range of motion (ROM), trunk lateral flexion, hip abduction and knee flexion ROM (P<0.05). Regression equations generated from these models effectively predicted peak knee extension, valgus and internal rotation moments (i. e., were not different from measured values P>0.05, ES<0.4) in the 20% subsample. 2D video-based measurements of an athlete's full body kinematics during unplanned sidestepping provide a reliable, specific, sensitive and cost-effective means for screening female team sport athletes.
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Hoy, M. G., R. F. Zernicke e J. L. Smith. "Contrasting roles of inertial and muscle moments at knee and ankle during paw-shake response". Journal of Neurophysiology 54, n. 5 (1 novembre 1985): 1282–94. http://dx.doi.org/10.1152/jn.1985.54.5.1282.
Testo completoAbstract (sommario):
Intralimb kinetics of the paw-shake response (PSR) were studied in four spinal, adult cats. Using rigid body equations of motion to determine the dynamic interactions between limb segments, knee and ankle joint kinetics were calculated for the steady-state cycles as defined in the preceding paper. Hindlimb motion was filmed (200 frames/s) to obtain knee and ankle kinematics. Responses of flexors and extensors at both joints were recorded synchronously with cinefilm. Ankle and knee joint kinematics were determined from 51 steady-state cycles of 16 PSRs. Average maximum displacements, velocities, and accelerations were substantially greater for the ankle than for the knee joint. Knee and ankle motions were out of phase in the first part of the cycle; knee extension occurred simultaneously with ankle flexion. In the second part of the cycle, motions at the two joints were sequential; rapid knee flexion, accompanied by negligible ankle displacement, preceded rapid ankle extension with minimal knee displacement. At the ankle joint, peak net moments tending to cause flexion and extension were similar in magnitude and determined primarily by muscle moments. Moments due to leg angular acceleration contributed significantly to an extensor peak in the net moment near the end of the cycle. Other inertial and gravitational moments were small. At the knee joint, net moments tending to cause flexion and extension were also similar, but smaller than those at the ankle. The knee muscle moments, however, were large and counteracted large inertial moments due to paw angular acceleration. Also, moments due to leg angular acceleration and knee linear acceleration were substantial and opposite in effect. Other inertial and the gravitational moments were negligible. Muscle moments slowed and reversed joint motions, and active muscle force components of muscle moments were derived from lengthening of active musculotendinous units. Segmental interactions, in which proximal segment motion augmented distal segment velocity, increased the effectiveness of PSR steady-state cycles by facilitating the generation of extremely large paw linear accelerations. Limb oscillations during PSR steady-state result from interactions between muscle synergies and motion-dependent limb dynamics. At the ankle, muscle activity functioned to control paw acceleration, whereas at the knee, muscle activity functioned to control leg and paw inertial interactions.(ABSTRACT TRUNCATED AT 400 WORDS)
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Sørensen, Henrik, Dennis B. Nielsen, Julie S. Jacobsen, Kjeld Søballe e Inger Mechlenburg. "Isokinetic dynamometry and gait analysis reveal different hip joint status in patients with hip dysplasia". HIP International 29, n. 2 (9 maggio 2018): 215–21. http://dx.doi.org/10.1177/1120700018773401.
Testo completoAbstract (sommario):
Background: Objective assessment of hip dysplasia patients’ functional hip joint status routinely involves gait analysis or isokinetic dynamometry. However, these methods have shown equivocal results and have not been employed in the same groups of patients and controls. Purpose: To assess hip flexor and abductor moments by isokinetic dynamometry in the dysplasia patient and controls, for which we previously reported smaller flexor and slightly larger abductor moments during gait in patients compared to controls. Methods: The study was designed as a prospective cohort study (Level of Evidence II) and conducted in a biomechanics laboratory at Aarhus University, Denmark, during 2011. Participants comprised 32 dysplasia patients and 32 age and gender matched controls. Outcome measures were static peak hip flexion moment at 15, 45 and 75° hip flexion; dynamic eccentric and concentric peak hip flexion moment at 60° and 120°/second; dynamic eccentric and concentric hip abductor moment at 30° and 60°/second. Results: Hip dysplasia patients had smaller eccentric peak flexion moments and smaller eccentric and concentric peak abduction moments at all tested velocities. Conclusion: Although dysplasia patients have weaker hip flexion and abductor muscles than controls, their abductor muscles are sufficiently strong to ensure normal function during gait. Hence, gait analysis alone might not reveal the true, subnormal hip joint status in dysplasia patients. We suggest that comprehensive assessment of hip joint function in dysplasia patients should include more strenuous activities than gait, particularly in young(er) patients who are likely to prefer a more active lifestyle.
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Lyle, Mark A., Jake C. Jensen, Jennifer L. Hunnicutt, Jonathan J. Brown, Cynthia P. Chambliss, Michael A. Newsome, John W. Xerogeanes e Liang-Ching Tsai. "Identification of strength and spatiotemporal gait parameters associated with knee loading during gait in persons after anterior cruciate ligament reconstruction". Journal of Athletic Training 2021, preprint (30 luglio 2021): 0000. http://dx.doi.org/10.4085/1062-6050-0186.21.
Testo completoAbstract (sommario):
ABSTRACT Context: Altered knee moments are common during gait in patients following anterior cruciate ligament reconstruction (ACLR). Modifiable factors that influence knee moments and are feasible to record in clinical settings such as strength and spatiotemporal parameters (e.g. step length, step width) have not been identified in persons after ACLR. Objective: The objective was to identify strength and spatiotemporal gait parameters that can predict knee moments in persons after ACLR. Design: Cross-Sectional Study Setting: Laboratory Patients: Twenty-three participants with ACLR (14.4 ± 17.2 months post-ACLR) participated. Main Outcome Measures: Peak knee flexion and adduction moments were measured while walking at self-selected speeds. Spatiotemporal gait parameters were recorded with a pressure walkway, and peak isokinetic knee extensor strength (60°/s) was recorded on a dynamometer. Pearson coefficients were used to examine the association of peak knee moments with strength and gait parameters. Variables correlated with peak knee flexion and adduction moments were entered into a stepwise regression model. Results: Step width and knee extensor strength were the strongest predictors of knee flexion moment accounting for 44% of data variance, whereas stance phase time and step width were the strongest predictors of knee adduction moment explaining 62% of data variance. Conclusions: The spatiotemporal variables that were identified could be clinically feasible targets for biofeedback to improve gait after ACLR.
Tesi sul tema "Moments de flexion des vagues"
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Kim, Shinwoong. "Experimental study on wave bending moments of a zero-speed rigid containership model in regular, irregular, and equivalent design waves". Electronic Thesis or Diss., Ecole centrale de Nantes, 2023. http://www.theses.fr/2023ECDN0001.
Testo completoAbstract (sommario):
La thèse vise à étudier les mouvements et les chargements internes d’un modèle de porte-conteneur rigide formé de 9 segments dans des vagues extrêmes. L’étude est principalement expérimentale et est réalisée avec une maquette sans vitesse d’avance dans une houle de face et une houle oblique (-120 degrés). L’étude aboutit à des résultats soulignant l’importance de la prendre en compte les aspects non linéaires des vagues et des réponses structurelles correspondantes.Dans des conditions de mer de face, trois types de vagues sont testés. Des vagues régulières sont utilisées pour s’assurer que le modèle se comporte de manière similaire à la campagne précédente effectuée avec la même maquette. Une approche de type Monte Carlo avec un certain nombre de réalisations de 2 heures 30 de vagues irrégulières est ensuite utilisée pour construire des données de référence. Enfin, des vagues equivalentes de design (EDW) sont générées pour vérifier, en particulier, la faisabilité d’une approche EDW irrégulière appelée First Order Reliability Method (FORM). Un algorithme numérique FORM couplé avec le solveur HOSNWT est développé et validé par rapport aux résultats Monte Carlo. Les caractéristiques géométriques des signaux EDW et VBM ainsi que leurs statistiques sont étudiées. L’étude vise peut-être deux quantités. Le premier est la hauteur de crête de la vague dans un scénario de vague seule, et le second est le VBM du modèle segmenté. L’utilisation du solveur de génération d’onde non linéaire HOS-NWT, permet une validation croisée avec la mesure expérimentale car les vagues générées sont comparables. Dans la condition de vagues obliques, l’étude est limitée aux vagues régulières avec différentes cambrure de vagues afin de fournir des données de référence pour les futures études. L’effet de non-linéarité des vagues sur les moments de flexion horizontaux et verticaux des vagues avec une cambrure variable est démontréThe present thesis aims to study the motions and the internal loads of a 9-segmented rigid containership model in extreme waves. The study is mainly experimental and is carried out on a zero-speed model in a 180-degree head sea and a -120 degree oblique sea. The study leads to results highlighting the importance of the consideration of nonlinear wave descriptions and corresponding nonlinear structural responses.In head sea conditions, three wave approaches are considered. Regular waves are used to ensure that the model behaves similar to the earlier campaign. A Monte Carlo approach with a number of full scale 2h30 irregular wave realizations is used to have reference data. Finally, irregular equivalent design waves (EDW) are studied to check, in particular, the feasibility of one irregular EDW approach called First Order Reliability Method.A numerical algorithm coupling with the HOS-NWT for the FORM EDW is developed and the validation compared to the Monte Carlo results is performed in terms of geometrical characteristics of the EDW and IW signals along with their statistics. The study targets mainly two quantities. The first is the wave crest in a wave-only scenario, and the second is the VBM of the segmented model. The use of the HOSNWT, a nonlinear wave generation solver, enables cross-validation with experimental measurement.In the oblique wave condition, the study is limited to regular waves with various wave steepness with the intent to provide reference data for future benchmark studies. The wave nonlinearity effect on the horizontal and vertical wave bending moments with varying steepness is shown
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Ndoumbe, Samuel. "Étude de la zone d'apparition des vagues à l'interface du film annulaire tombant". Vandoeuvre-les-Nancy, INPL, 2001. http://www.theses.fr/2001INPL582N.
Testo completoAbstract (sommario):
Cette thèse porte sur l'étude de l'écoulement d'un film liquide mince visqueux tombant sous l'effet de la gravité à l'intérieur d'une conduite cylindrique verticale. L'objectif principal de ce travail est la caractérisation à la fois théorique et expérimentale de la surface du film. Celle-ci se fait sur le plan théorique par le développement d'un modèle 3D à grand nombre de Reynolds et à grande longueur d'onde, dont les principales inconnues sont l'épaisseur instantanée et les débits axial et azimutal. Sur le plan expérimental, on mesure l'épaisseur instantanée avec des sondes conductimétriques affleurantes en 8 positions de la conduite. A partir de l'analyse statistique et dynamique de cette épaisseur, l'étude de la stabilité linéaire et faiblement non linéaire du modèle a été validée via la détermination de la célérité des vagues, la fonction de transfert, les fréquences prépondérantes. Nous avons montré que la structure de l'interface est à la fois dépendante du nombre de Reynolds et de la distance au point d'injection du liquide.
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Khairi, Refzul. "Modélisation de la diffusion électromagnétique par les vagues côtières déferlantes". Phd thesis, Université de Bretagne occidentale - Brest, 2013. http://tel.archives-ouvertes.fr/tel-00839745.
Testo completoAbstract (sommario):
L'objectif de ce travail de thèse est d'étudier l'interaction des ondes électromagnétiques en bande L avec les vagues côtières déferlantes, en particulier pour un observateur situé à proximité de la surface. Le travail s'attache à effectuer une modélisation électromagnétique précise en lien étroit avec le modèle hydrodynamique. Pour modéliser et calculer les champs électromagnétiques diffusés par les vagues déferlantes, nous utilisons une approche numérique par intégrale de frontière, notamment la Méthode des Moments (MdM). Dans ce cadre, nous focalisons le travail sur la problématique de la fiabilité et la convergence du calcul numérique pour des géométries de forte courbure comme peuvent l'être des surfaces de vagues déferlantes. Après une analyse approfondie de la problématique, nous montrons qu'une solution fondée sur la Méthode des Moments d'Ordre Supérieur (MdM-OS) combinée avec la technique de maillage Non Uniform Rational Basis Splines (NURBS) permet d'améliorer les performances de la méthode MdM-Classique. En parallèle du travail de modélisation électromagnétique, nous nous attachons à introduire un modèle hydrodynamique capable de simuler le plus fidèlement possible le mouvement et la déformation des vagues à proximité de la côte. Nous retenons une modélisation hydrodynamique basée sur la Méthode Désingularisée. Cette approche méthodologique nous permet d'étudier l'évolution des vagues en fonction de la pente du fond, de la hauteur relative et de la cambrure des vagues. La combinaison des résultats issus de la modélisation numérique électromagnétique et de la description hydrodynamique permettent ainsi d'évaluer l'évolution des champs électromagnétiques diffusés par les vagues côtières déferlantes en fonction du temps pour trois types de déferlement standard : glissant, plongeant et gonflant.
Libri sul tema "Moments de flexion des vagues"
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Carnet Diabetique V2 V8 Editions. Carnet de Diab�te: Carnet Diabetique Avec Suivi de Glyc�mie Sur 53 Semaines - 111 Pages, 15,24 X 22,86cm - Broch� - Avant Apr�s, 5 Moments de la Journ�e - Photo Oc�an Bleu Turquoise Vagues. Independently Published, 2019.
Cerca il testo completoCapitoli di libri sul tema "Moments de flexion des vagues"
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Alt, Tobias, Kevin Nolte, Dennis Horn, Dominik Modenbach, Axel Johannes Knicker e Thomas Jaitner. "Effects of Test Modality and Hip Flexion on Resultant Knee Flexor Moments". In 13th World Congress of Performance Analysis of Sport and 13th International Symposium on Computer Science in Sport, 31–34. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-31772-9_7.
Testo completo
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Braune, Wilhelm, e Otto Fischer. "Example of Application of the Moments of Inertia Thus Found: Determination of the Period of Oscillation of the Leg at Different Degrees of Flexion". In Determination of the Moments of Inertia of the Human Body and Its Limbs, 75–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-662-11236-6_5.
Testo completoAtti di convegni sul tema "Moments de flexion des vagues"
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Umale, Sagar, John R. Humm e Narayan Yoganandan. "Effects of Personal Protective Equipment on Spinal Column Loads From Underbody Blast Loading". In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73664.
Testo completoAbstract (sommario):
Abstract Combat-related spine injuries from improvised explosive devices are attributed to vertical loading transmitted from the seat to the pelvis to the torso and head-neck regions. The presence of personal protective equipment (PPE) adds to the weight of the torso, influencing the load transmission within the vertebral column. In this study, a detailed mid-size male finite element model from the Global Human Body Models Consortium was used to investigate the effect of PPE on spine kinematics, forces, and moments along the vertebral column. The model was positioned on a rigid seat, such that the posture represented an upright seated soldier. Once positioned, the model was updated with PPE. The models, with and without PPE were simulated under two high acceleration vertical loading pulses and the spine accelerations, forces and moments were investigated. The PPE increased the spinal loads, with reduced time to peak. The presence of PPE increased forces in the cervical and thoracic spines up to 14% and 9%, while it decreased the lumbar spine forces up to 7%. PPE increased cervical spine extension moment up to 104%, thoracic spine flexion moment up to 14%, and decreased the lumbar spine flexion moment up to 11%. The increase in thoracic spine compressive forces and flexion moments due to PPE suggest increased risk of injury in compression-flexion, such as anterior or burst fractures of the thoracic vertebrae with or without the distraction of posterior elements/ligaments. Whereas, the PPE may be effective in reducing the injury in lumbar spine, with reduced forces and moments. The pulse variation showed that the seat velocity along with the acceleration influence the spine kinematics and further parametric studies are needed to understand the effectiveness of PPE for varying seat velocities/accelerations. Spinal accelerations peaked earlier with PPE; however, their peak and morphologies were unchanged. This study delineates the kinetics of the spine injury during underbody blast loading and the role of PPE on potential injuries and injury mechanisms based on forces and moments.
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Mesfar, Wissal, e Kodjo Moglo. "Effect of Head Weight on the Biomechanics of a Cervical Spine Under Extension and Flexion Moments". In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-38767.
Testo completoAbstract (sommario):
The determination of head and neck biomechanics is one of the keys for deep understanding of impairments in neck function and cervical spine pathologies. Finite element models are a valuable tool to perform parametric studies. In this study, we aim to investigate the effect of a 40N head weight on the biomechanics of the head and neck complex under flexion-extension moments. The loading is applied to the centre of mass of the head and the first thoracic vertebra is fixed. Our predictions show that the kinematics and the load distribution at the facet joints were altered significantly with considering of the head weight under the flexion and extension movements. Our investigations indicate the substantial role of the head weight on the biomechanical behavior of the cervical spine and suggest its consideration in comparing the models predictions with the measurements.
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Kiapour, A., M. Parnianpour e A. Shirazi-Adl. "Control of Different FEM Based Musculoskeletal Models of Human Lumbar Spine Under Different Loading Conditions Using Optimization Method". In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95224.
Testo completoAbstract (sommario):
In this study the effects of using different musculoskeletal models on load-displacement behavior of FE models of the human lumbar spine under external loads and moments have been analyzed in terms of equilibrium and clinical stability. A simplified and a complex architecture of muscles have been integrated to FE based models of lumbar spine and were loaded to simulate the load carrying behavior of human lumbar spine in flexion, extension and lateral bending. The displacement values as well as muscle forces have been computed and compared in both cases using optimization methods with different cost functions. The models showed similar kinematics in pure flexion but the simplified model showed instability in flexion-lateral bending and pure lateral bending conditions. The complex model was loaded and analyzed with different cost function and it was observed that displacements in the model are lower while the angle between the load vector and spine curvature at each level is minimized. It was shown that the model is less stable in case an asymmetric loading condition is applied.
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Nessler, Jeff A., Winsean Lin e Yasin Dhaher. "Synergistic Moments at the Hip and Knee Joints Are Altered in Post-Stroke Hemiplegic Gait". In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-175864.
Testo completoAbstract (sommario):
Following stroke, many patients are unable to adequately bend their knee during the swing phase of gait [1,2]. This loss of functional control may be related to an abnormal muscle synergy or torque couple in the lower limb, similar to those reported for the upper extremity [3–5]. For example, several investigators have described a flexor synergy that couples shoulder abduction torque and elbow flexion torque under static, isometric conditions [3–4]. This couple is typically altered following stroke [3–4]. In the lower extremity, hip kinetics in the frontal plane appear to be coupled with knee kinetics in the sagittal plane for static, isometric conditions [6]. It is unknown, however, whether the same relationship holds for hip and knee kinetics under dynamic conditions, such as during the swing phase of gait.
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Huang, Changhua, Nianfeng Yang, Rencheng Wang, Changhong Zhu e Dewen Jin. "Redundant Muscular Force Analysis of Lower Extremity During Swing Phase". In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0497.
Testo completoAbstract (sommario):
Abstract Swing phase of the human gait is defined as the time period during the bottom of foot is off the ground. At the beginning of swing phase there is a flexion of knee joint, which is important to form the clearance between the ground and the toe. In 1992 Winter referred to that the average clearance is about 1.29cm in a normal swing phase and mainly dominated by the flexion of the knee joint. If there doesn’t have enough flexion of knee, the tiptoe will collide with the ground during the swing phase. Otherwise, in this case, there must be an additional trunk movement to raise the coxa joint or to abduct the thigh. Actually this is not a normal gait and looks very clumsy as you can imagine a patient’s gait. However, regarding how to obtain the enough flexion of knee, people have different views on that whether the muscles of lower limb are actively involved and how much contribution they make. Mochaon and McMahon (1980) stated that at a certain extent of initial angular velocity, the clearance can be obtained without muscles’ involving. Mena (1981) also referred to that an approximated normal swing phase could be simulated without applying moments on the coxa joint and/or knee joint. But later, researchers got different results. Yamaguchi (1990) found that there should be muscular forces in swing phase through a simulation analysis of 8-DOF musculoskeletal model with dynamic programming method. With limiting solution method. Collins (1995) got the similar conclusion. In 1996. Piazza and Delp presented a 3-DOF musculoskletetal model to study the effects of muscular forces on knee flexion, they decreased or increased the strength of the neural innervation signals of some muscles and made a thorough observation on the movement of lower limbs. In their discussions the importance of rectus femoris (RF) in knee flexion was emphasized.
6
Shirazi-Adl, A., e M. Parnianpour. "Response of the Lumbar Spine in Large Compression Loads: Stability Demands in Neutral Postures". In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-1234.
Testo completoAbstract (sommario):
Abstract In neutral standing and sitting postures, the human lumbar spine is known to be subjected to both compression force and flexion/lateral moments. For the whole trunk, the centre of mass has been reported to be about 2.0 cm anterior to the L1-L2 vertebral centroid [1]. Due to the asymmetry of the upper body about the sagittal plane, lateral moments likely exist as well. The magnitude of these moments is affected by the location of the line of gravity relative to the vertebrae, and therefore, by the spinal posture (ie, pelvic rotation and lumbar lordosis). Changes in the sagittal curvature of the human lumbar spine (ie, lordosis) has been recorded under external loads and in microgravity [2–4]. Smaller lordosis has been observed in standing radiographs of low-back pain population compared with those of normal volunteers [5]. The preservation of lordosis and its biomechanical consequences during daily activities and heavy lifting tasks remain still as a controversial issue.
7
DeVries, Nicole A., Anup A. Gandhi, Douglas C. Fredericks, Joseph D. Smucker e Nicole M. Grosland. "In Vitro Study of the C2-C7 Sheep Cervical Spine". In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53167.
Testo completoAbstract (sommario):
Due to the limited availability of human cadaveric specimens, animal models are often utilized for in vitro studies of various spinal disorders and surgical techniques. Sheep spines have similar geometry, disc space, and lordosis as compared to humans [1,2]. Several studies have identified the geometrical similarities between the sheep and human spine; however these studies have been limited to quantifying the anatomic dimensions as opposed to the biomechanical responses [2–3]. Although anatomical similarities are important, biomechanical correspondence is imperative to understand the effects of disorders, surgical techniques, and implant designs. Some studies [3–5] have focused on experimental biomechanics of the sheep cervical functional spinal units (FSUs). Szotek and colleagues [1] studied the biomechanics of compression and impure flexion-extension for the C2-C7 intact sheep spine. However, to date, there is no comparison of the sheep spine using pure flexion-extension, lateral bending, or axial rotation moments for multilevel specimen. Therefore, the purpose of this study was to conduct in vitro testing of the intact C2-C7 sheep cervical spine.
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Schimoler, Patrick J., Jeffrey S. Vipperman, Laurel Kuxhaus, Angela M. Flamm, Daniel D. Budny, Mark E. Baratz e Mark Carl Miller. "Control System for an Elbow Joint Motion Simulator". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42806.
Testo completoAbstract (sommario):
The many muscles crossing the elbow joint allow for its motions to be created from different combinations of muscular activations. Muscles are strictly contractile elements and the joints they surround rely on varying loads from opposing antagonists for stability and movement. In designing a control system to actuate an elbow in a realistic manner, unidirectional, tendon-like actuation and muscle co-activation must be considered in order to successfully control the elbow’s two degrees of freedom. Also important is the multifunctionality of certain muscles, such as the biceps brachii, which create moments impacting both degrees of freedom: flexion / extension and pronation / supination. This paper seeks to develop and implement control algorithms on an elbow joint motion simulator that actuates cadaveric elbow specimens via four major muscles that cross the elbow joint. The algorithms were validated using an anatomically-realistic mechanical elbow. Clinically-meaningful results, such as the evaluation of radial head implants, can only be obtained under repeatable, realistic conditions; therefore, physiologic motions must be created by the application of appropriate loads. This is achieved by including load control on the muscles’ actuators as well as displacement control on both flexion / extension and supination / pronation.
9
Meghdari, Ali, e Amir H. Bahrami. "Mathematical Modeling of Normal, Degenerated, and Fused Cervical Spines Using IAR’S Concept". In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23038.
Testo completoAbstract (sommario):
Abstract During flexion/extension, of the head-neck system, cervical spine undergoes a stepwise motion from the upper to lower regions with a specific time lag. Motion of each vertebrae is composed of a translation and a rotation with respect to lower vertebrae, which may be considered as an absolute rotation about an axis called Instantaneous Axis of Rotation (IAR). Location of this axis is different between normal, and degenerated spines. In this research intersegmental force-moments are evaluated and compared in normal, degenerated, and fused subjects employing a biomechanical model of head-neck system based on IAR’s concept and the results are presented.
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Li, Siping, Anita N. Vasavada e Scott L. Delp. "Effect of Cervical Spine Position on Moment-Generating Potentials of Neck Muscles". In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0311.
Testo completoAbstract (sommario):
Abstract The stability of the head/neck system is achieved through the interplay of the passive ligamentous cervical spine and active neck musculature under neural control (Panjabi, 1992). Neck muscles provide forces and moments to generate movements of head/neck and maintain their stability. Many previous analyses have used muscle geometry at the neutral head position to calculate the forces and moments produced by the muscles. These studies, in general, have not examined how changes of muscle moment arms and muscle lengths affect their force and moment-generating capacities. It is yet not clear how the moment-generating capacities of individual neck muscles vary and how their relative contributions to total strength change with head/neck posture. Quantification of the moment-generating potentials of individual neck muscles at different positions of the cervical spine will provide insight into the contributions of the neck muscles to head movement and spine stabilization. The objective of this study was to quantify the variation of maximal isometric moment-generating potentials of neck muscles with flexion-extension, lateral bending, and axial rotation.