Articles de revues : « Biomechanical variable »

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Ardestani, Marzieh M., Christopher E. Henderson, Gordhan Mahtani, Mark Connolly et T. George Hornby. « Locomotor Kinematics and Kinetics Following High-Intensity Stepping Training in Variable Contexts Poststroke ». Neurorehabilitation and Neural Repair 34, n^o 7 (6 juin 2020) : 652–60. http://dx.doi.org/10.1177/1545968320929675.

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Background and Purpose. Previous studies suggest that individuals poststroke can achieve substantial gains in walking function following high-intensity locomotor training (LT). Recent findings also indicate practice of variable stepping tasks targeting locomotor deficits can mitigate selected impairments underlying reduced walking speeds. The goal of this study was to investigate alterations in locomotor biomechanics following 3 different LT paradigms. Methods. This secondary analysis of a randomized trial recruited individuals 18 to 85 years old and >6 months poststroke. We compared changes in spatiotemporal, joint kinematics, and kinetics following up to 30 sessions of high-intensity (>70% heart rate reserve [HRR]) LT of variable tasks targeting paretic limb and balance impairments (high-variable, HV), high-intensity LT focused only on forward walking (high-forward, HF), or low-intensity LT (<40% HRR) of variable tasks (low-variable, LV). Sagittal spatiotemporal and joint kinematics, and concentric joint powers were compared between groups. Regressions and principal component analyses were conducted to evaluate relative contributions or importance of biomechanical changes to between and within groups. Results. Biomechanical data were available on 50 participants who could walk ≥0.1 m/s on a motorized treadmill. Significant differences in spatiotemporal parameters, kinematic consistency, and kinetics were observed between HV and HF versus LV. Resultant principal component analyses were characterized by paretic powers and kinematic consistency following HV, while HF and LV were characterized by nonparetic powers. Conclusion. High-intensity LT results in greater changes in kinematics and kinetics as compared with lower-intensity interventions. The results may suggest greater paretic-limb contributions with high-intensity variable stepping training that targets specific biomechanical deficits. Clinical Trial Registration. https://clinicaltrials.gov/ Unique Identifier: NCT02507466

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Post, Andrew, T. Blaine Hoshizaki, Michael D. Gilchrist, David Koncan, Lauren Dawson, Wesley Chen, Andrée-Anne Ledoux, Roger Zemek et _. _. « A comparison in a youth population between those with and without a history of concussion using biomechanical reconstruction ». Journal of Neurosurgery : Pediatrics 19, n^o 4 (avril 2017) : 502–10. http://dx.doi.org/10.3171/2016.10.peds16449.

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OBJECTIVE Concussion is a common topic of research as a result of the short- and long-term effects it can have on the affected individual. Of particular interest is whether previous concussions can lead to a biomechanical susceptibility, or vulnerability, to incurring further head injuries, particularly for youth populations. The purpose of this research was to compare the impact biomechanics of a concussive event in terms of acceleration and brain strains of 2 groups of youths: those who had incurred a previous concussion and those who had not. It was hypothesized that the youths with a history of concussion would have lower-magnitude biomechanical impact measures than those who had never suffered a previous concussion. METHODS Youths who had suffered a concussion were recruited from emergency departments across Canada. This pool of patients was then separated into 2 categories based on their history of concussion: those who had incurred 1 or more previous concussions, and those who had never suffered a concussion. The impact event that resulted in the brain injury was reconstructed biomechanically using computational, physical, and finite element modeling techniques. The output of the events was measured in biomechanical parameters such as energy, force, acceleration, and brain tissue strain to determine if those patients who had a previous concussion sustained a brain injury at lower magnitudes than those who had no previously reported concussion. RESULTS The results demonstrated that there was no biomechanical variable that could distinguish between the concussion groups with a history of concussion versus no history of concussion. CONCLUSIONS The results suggest that there is no measureable biomechanical vulnerability to head impact related to a history of concussions in this youth population. This may be a reflection of the long time between the previous concussion and the one reconstructed in the laboratory, where such a long period has been associated with recovery from injury.

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Lacarbonara, Mariano, Ettore Accivile, Maria R. Abed, Maria Teresa Dinoi, Annalisa Monaco, Giuseppe Marzo et Mario Capogreco. « Variable Torque Prescription : State of Art. » Open Dentistry Journal 9, n^o 1 (30 janvier 2015) : 60–64. http://dx.doi.org/10.2174/1874210601509010060.

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The variable prescription is widely described under the clinical aspect: the clinics is the result of the evolution of the state-of-the-art, aspect that is less considered in the daily literature. The state-of-the-art is the key to understand not only how we reach where we are but also to learn how to manage propely the torque, focusing on the technical and biomechanical purpos-es that led to the change of the torque values over time. The aim of this study is to update the clinicians on the aspects that affect the torque under the biomechanical sight, helping them to understand how to managing it, following the “timeline changes” in the different techniques so that the Variable Prescription Orthodontic (VPO) would be a suitable tool in every clinical case.

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Tidwell, John E., Evan P. Roush, Cassandra L. Ondeck, Allen R. Kunselman, J. Spence Reid et Gregory S. Lewis. « The biomechanical cost of variable angle locking screws ». Injury 47, n^o 8 (août 2016) : 1624–30. http://dx.doi.org/10.1016/j.injury.2016.06.001.

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Post, Andrew, Eyesha Hashim, Windsor Kwan-Chun Ting, T. Blaine Hoshizaki, Michael D. Gilchrist et Michael D. Cusimano. « A preliminary analysis of biomechanics and saccadic responses for concussion ». Trauma 22, n^o 3 (19 juillet 2019) : 182–92. http://dx.doi.org/10.1177/1460408619861026.

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Background Concussion is an injury that occurs in non-sporting and sporting environments. To determine improved clinical methods for identifying this injury, it is important to develop and understand how the impact event results in quantifiable differences in brain functioning—functioning that has been quantified in the past using saccadic measures. The purpose of this research was to examine the relationships between oculomotor deficits, specifically antisaccade responses, and the biomechanics of impact for a concussion. Methods Participants underwent a diffusion tensor imaging protocol as well as saccadic testing to determine differences in brain functioning in comparison to controls. The injury event was then reconstructed in laboratory using physical and finite element models to determine the biomechanics of the impact and brain tissue strain. Relationships between the biomechanical variables and antisaccade responses were then examined. Results The diffusion tensor imaging analyses found that there was a decrease in radial diffusivity and axial diffusivity found in the cerebral peduncle (p < 0.05) and cingulum hippocampus (p < 0.05), respectively. There was an increase in the axial diffusivity for the corona radiata (p < 0.05). The saccadic testing found an increase in mean latency for the concussed group (p < 0.05). The results indicated no significant relationship between mean latency, duration, amplitude and peak velocity antisaccade measures and the biomechanical variables. This may have been influenced not only by a lack of sensitivity in biomechanical variable to antisaccade responses, but also to these responses being affected by factors other than injury such as attentiveness and wakefulness. Conclusion While the sample of this research was small, this research suggests that to improve the understanding of the relationship between impact biomechanics and concussion, methods that can quantify the damage to brain structures through imaging, such as diffusion tensor imaging, may be more appropriate.

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Schutte, Jaco F., Byung-Il Koh, Jeffrey A. Reinbolt, Raphael T. Haftka, Alan D. George et Benjamin J. Fregly. « Evaluation of a Particle Swarm Algorithm For Biomechanical Optimization ». Journal of Biomechanical Engineering 127, n^o 3 (31 janvier 2005) : 465–74. http://dx.doi.org/10.1115/1.1894388.

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Optimization is frequently employed in biomechanics research to solve system identification problems, predict human movement, or estimate muscle or other internal forces that cannot be measured directly. Unfortunately, biomechanical optimization problems often possess multiple local minima, making it difficult to find the best solution. Furthermore, convergence in gradient-based algorithms can be affected by scaling to account for design variables with different length scales or units. In this study we evaluate a recently- developed version of the particle swarm optimization (PSO) algorithm to address these problems. The algorithm’s global search capabilities were investigated using a suite of difficult analytical test problems, while its scale-independent nature was proven mathematically and verified using a biomechanical test problem. For comparison, all test problems were also solved with three off-the-shelf optimization algorithms—a global genetic algorithm (GA) and multistart gradient-based sequential quadratic programming (SQP) and quasi-Newton (BFGS) algorithms. For the analytical test problems, only the PSO algorithm was successful on the majority of the problems. When compared to previously published results for the same problems, PSO was more robust than a global simulated annealing algorithm but less robust than a different, more complex genetic algorithm. For the biomechanical test problem, only the PSO algorithm was insensitive to design variable scaling, with the GA algorithm being mildly sensitive and the SQP and BFGS algorithms being highly sensitive. The proposed PSO algorithm provides a new off-the-shelf global optimization option for difficult biomechanical problems, especially those utilizing design variables with different length scales or units.

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Martens, Géraldine, Dorian Deflandre, Cédric Schwartz, Nadia Dardenne et Thierry Bury. « Reproducibility of the Evolution of Stride Biomechanics During Exhaustive Runs ». Journal of Human Kinetics 64, n^o 1 (15 octobre 2018) : 57–69. http://dx.doi.org/10.1515/hukin-2017-0184.

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Abstract Running biomechanics and its evolution that occurs over intensive trials are widely studied, but few studies have focused on the reproducibility of stride evolution in these runs. The purpose of this investigation was to assess the reproducibility of changes in eight biomechanical variables during exhaustive runs, using three-dimensional analysis. Ten male athletes (age: 23 ± 4 years; maximal oxygen uptake: 57.5 ± 4.4 ml02·min-1·kg-1; maximal aerobic speed: 19.3 ± 0.8 km·h-1) performed a maximal treadmill test. Between 3 to 10 days later, they started a series of three time-to-exhaustion trials at 90% of the individual maximal aerobic speed, seven days apart. During these trials eight biomechanical variables were recorded over a 20-s period every 4 min until exhaustion. The evolution of a variable over a trial was represented as the slope of the linear regression of these variables over time. Reproducibility was assessed with intraclass correlation coefficients and variability was quantified as standard error of measurement. Changes in five variables (swing duration, stride frequency, step length, centre of gravity vertical and lateral amplitude) showed moderate to good reproducibility (0.48 ≤ ICC ≤ 0.72), while changes in stance duration, reactivity and foot orientation showed poor reproducibility (-0.71 ≤ ICC ≤ 0.04). Fatigue-induced changes in stride biomechanics do not follow a reproducible course across the board; however, several variables do show satisfactory stability: swing duration, stride frequency, step length and centre of gravity shift.

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Palma, Felipe H., Sebastián Cisternas Rodríguez, Francisco Vargas Buton, Marcela Olmos Nieva, Günther Redenz et Rodrigo Guzmán-Venegas. « Correlation between clinical tests for gait and stability using biomechanical variables in the gait of institutionalized elderly subjects ». Biomedical Human Kinetics 13, n^o 1 (1 janvier 2021) : 49–55. http://dx.doi.org/10.2478/bhk-2021-0007.

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Abstract Study aim: This study aims to identify biomechanical gait variables explaining clinical test results in institutionalized elderly people. Material and methods: Twenty-nine elderly (82.0 ± 6.3 years) residents in a nursing home were assessed. They were able to walk 10 meters without walking aids. First, the spontaneous gait was assessed using inertial measurement units in a 10-meter long corridor. Fifteen biomechanical gait variables were analyzed. Then, three clinical tests usually used in elderly subjects were applied: the Timed Up and Go (TUG) test, the Tinetti Scale and the Sit to Stand (STS) test. A correlation matrix using Pearson’s correlation coefficient between clinical and biomechanical variables was performed, obtaining a total of 45 potential correlations. A stepwise multiple linear regression analysis was then performed to determine the influence of each variable. Results: TUG, Tinetti and STS were significantly correlated with similar biomechanical variables, including temporal, temporo-spatial and kinematic variables. Adults over 80 years old and women showed stronger correlations. Single support and ankle angle at takeoff were the two most important variables in stepwise regression analysis. Conclusions: In institutionalized elderly subjects, clinical variables for gait and postural stability are correlated with the biomechanical gait variables, especially in women and adults aged over 80 years.

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Gerhardt, Michael B., Benjamin S. Assenmacher et Jorge Chahla. « Proximal Hamstring Repair : A Biomechanical Analysis of Variable Suture Anchor Constructs ». Orthopaedic Journal of Sports Medicine 7, n^o 2 (1 février 2019) : 232596711882414. http://dx.doi.org/10.1177/2325967118824149.

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Background: Despite an abundance of literature regarding construct strength for a myriad of anchors and anchor configurations in the shoulder, there remains a paucity of biomechanical studies detailing the efficacy of these implants for proximal hamstring repair. Purpose: To biomechanically evaluate the ultimate failure load and failure mechanism of knotless and knotted anchor configurations for hamstring repair. Study Design: Controlled laboratory study. Methods: A total of 17 cadaveric specimens divided into 3 groups composed of intact hamstring tendons as well as 2 different anchor configurations (all-knotted and all-knotless) underwent first cyclic loading and subsequent maximal loading to failure. This protocol entailed a 10-N preload, followed by 100 cycles incrementally applied from 20 to 200 N at a frequency of 0.5 Hz, and ultimately followed by a load to failure with a loading rate of 33 mm/s. The ultimate failure load and mechanism of failure were recorded for each specimen, as was the maximal displacement of each bone-tendon interface subsequent to maximal loading. Analysis of variance was employed to calculate differences in the maximal load to failure as well as the maximal displacement between the 3 study groups. Holm-Sidak post hoc analysis was applied when necessary. Results: The all-knotless suture anchor construct failed at the highest maximal load of the 3 groups (767.18 ± 93.50 N), including that for the intact tendon group (750.58 ± 172.22 N). There was no statistically significant difference between the all-knotless and intact tendon groups; however, there was a statistically significant difference in load to failure when the all-knotless construct was compared with the all-knotted technique (549.56 ± 20.74 N) ( P = .024). The most common mode of failure in both repair groups was at the suture-tendon interface, whereas the intact tendon group most frequently failed via avulsion of the tendon from its insertion site. Conclusion: Under biomechanical laboratory testing conditions, proximal hamstring repair using all-knotless suture anchors outperformed the all-knotted suture anchor configuration with regard to elongation during cyclic loading and maximal load to failure. Failure in the all-knotted repair group was at the suture-tendon interface in most cases, whereas the all-knotless construct failed most frequently at the musculotendinous junction. Clinical Relevance: No biomechanical studies have clearly identified the optimal anchor configuration to avert proximal hamstring repair failure. Delineating this ideal suture anchor construct and its strength compared with an intact hamstring tendon may alter the current standards for postoperative rehabilitation, which remain extremely conservative and onerous for these patients.

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Hamandi, Farah, Gerard Simon, Richard Laughlin et Tarun Goswami. « Biomechanical Behavior of a Variable Angle Locked Tibiotalocalcaneal Construct ». Bioengineering 7, n^o 1 (14 mars 2020) : 27. http://dx.doi.org/10.3390/bioengineering7010027.

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This paper examines the mechanics of the tibiotalocalcaneal construct made with a PHILOS plating system. A failed device consisting of the LCP plate and cortical, locking, and cannulated screws was used to perform the analysis. Visual, microstructure, and fractographic examinations were carried out to characterize the fracture surface topology. These examinations revealed the presence of surface scratching, inclusions, discoloration, corrosion pits, beach marks, and cleavage and striations on the fracture surface. Further examination of the material crystallography and texture revealed an interaction of S, Ni, and Mo-based inclusions that may have raised pitting susceptibility of the device made with Stainless Steel 316L. These features suggest that the device underwent damage by pitting the corrosion-fatigue mechanism and overloading towards the end to fail the plate and screws in two or more components. The screws failed via conjoint bending and torsion fatigue mechanisms. Computer simulations of variable angle locking screws were performed in this paper. The material of construction of the device was governed by ASTM F138-8 or its ISO equivalent 5832 and exhibited inconsistencies in chemistry and hardness requirements. The failure conditions were matched in finite element modeling and those boundary conditions discussed in this paper.

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Friedel, Roland, Yong Huang, Rut Tejero, Chrystian Junqueira Alves, Concetta Brusco, Theodore Hannah, Vivian Lee, Guohao Dai et Hongyan Zou. « TAMI-60. MODULATION OF CELL BIOMECHANICS THROUGH GUIDANCE RECEPTOR PLEXIN-B2 FACILITATES GLIOBLASTOMA INFILTRATION ». Neuro-Oncology 23, Supplement_6 (2 novembre 2021) : vi210—vi211. http://dx.doi.org/10.1093/neuonc/noab196.842.

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Abstract Infiltrative growth is a major cause of the high lethality of malignant brain tumors such as glioblastoma (GBM). The study of the contribution of biomechanical processes to GBM invasion is an emerging field. We show here that GBM cells upregulate the guidance receptor Plexin-B2 to gain invasiveness by modulating their biomechanical properties. Deletion of Plexin-B2 in GBM stem cells limited tumor spread and shifted invasion paths from axon fiber tracts to perivascular routes. On a cellular level, Plexin-B2 adjusts cell adhesiveness, migratory responses to different matrix stiffness, and actomyosin dynamics, thus empowering GBM cells to leave stiff tumor bulk and infiltrate softer brain parenchyma. Correspondingly, gene signatures affected by Plexin-B2 were associated with locomotor regulation, matrix interactions, and cellular biomechanics. On a molecular level, the intracellular Ras-GAP domain contributed to Plexin-B2 function, while the signaling relationship with downstream effectors Rap1/2 appeared variable between GBM stem cell lines, reflecting intertumoral heterogeneity. Our studies have established Plexin-B2 as a modulator of cell biomechanics that is usurped by GBM cells to gain invasiveness. Ongoing investigations focus on the regulation of the biomechanical properties of cell membrane and cell actomyosin cortex through plexins that provide GBM cells with the mechanical dynamics to penetrate to restricted space.

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Pérez-Rueda, Antonio, Diana Jiménez-Rodríguez et Gracia Castro-Luna. « Diagnosis of Subclinical Keratoconus with a Combined Model of Biomechanical and Topographic Parameters ». Journal of Clinical Medicine 10, n^o 13 (22 juin 2021) : 2746. http://dx.doi.org/10.3390/jcm10132746.

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This study sought to develop a diagnostic model with aberrometry and biomechanical variables for subclinical keratoconus. The design was a cross-sectional study. The topographic data were obtained with a rotating Scheimpflug camera (Pentacam HR), and biomechanical data were obtained with Corvis ST. The study included 81 eyes distributed in 61 healthy corneas and 20 subclinical keratoconus (SCKC), defined as eyes with suspicious topographic findings, normal slit-lamp examination, and a manifestation of keratoconus. Analyses of the topographic and biomechanical data were performed, and a classifying model of SCKC was elaborated. The model for the diagnosis of SCKC includes posterior coma to 90°, Ambrósio’s Relational Thickness in the horizontal profile (ARTh), and velocity when the air pulse is off (A2 velocity). The sensitivity was 89.5%, specificity 96.7%, accuracy 94.9%, and precision 89.5%. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve for the model was 0.951. Diagnosis of subclinical keratoconus depends on the aberrometry variable posterior coma to 90° and the biomechanical variables A2 velocity and ARTh.

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Williams, K. R., et P. R. Cavanagh. « Relationship between distance running mechanics, running economy, and performance ». Journal of Applied Physiology 63, n^o 3 (1 septembre 1987) : 1236–45. http://dx.doi.org/10.1152/jappl.1987.63.3.1236.

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The relationships between biocmechanical aspects of distance running, running economy (VO2 submax), and performance were investigated. A variety of biomechanical measures for 31 subjects running at 3.6 m/s was obtained, including three-dimensional angular and translational kinematics, ground reaction forces and center of pressure patterns, mechanical power, and anthropometric measures. Physiological measures obtained included maximal and submaximal O2 consumption, muscle fiber composition, and measures of the ability to store and return elastic energy during knee bends. A subset of 16 runners was also evaluated in relation to performance in a 10-km run. Biomechanical variables were identified which showed significant differences or consistent trends between groups separated on the basis of VO2 submax, establishing the importance of biomechanical influences on running economy. It appears that no single variable or small subset of variables can explain differences in economy between individuals but rather that economy is related to a weighted sum of the influences of many variables.

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Gamit, Amit K. « The Relationship of Selected Anthropometric and Biomechanical Variable with the Performance of Volleyball Player ». Indian Journal of Applied Research 3, n^o 3 (1 octobre 2011) : 315–16. http://dx.doi.org/10.15373/2249555x/mar2013/105.

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King, Enda, Chris Richter, Andy Franklyn-Miller, Ross Wadey, Ray Moran et Siobhan Strike. « Back to Normal Symmetry ? Biomechanical Variables Remain More Asymmetrical Than Normal During Jump and Change-of-Direction Testing 9 Months After Anterior Cruciate Ligament Reconstruction ». American Journal of Sports Medicine 47, n^o 5 (avril 2019) : 1175–85. http://dx.doi.org/10.1177/0363546519830656.

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Background: After anterior cruciate ligament reconstruction (ACLR), athletes have demonstrated performance asymmetries as compared with healthy cohorts, but little research has investigated if biomechanical asymmetries are also different during jump and change-of-direction (CoD) tasks between groups. Purpose: To identify if differences in magnitude of asymmetry of biomechanical and performance variables exist between these groups. Study Design: Controlled laboratory study. Methods: Analysis was conducted between 156 male patients 9 months after surgery and 62 healthy participants. Three-dimensional motion capture and analysis were carried out on a double-legged drop jump, a single-legged drop jump, a single-legged hop for distance, and planned and unplanned CoD. Asymmetry between limbs was calculated for each variable with root mean square difference between limbs. Statistical parametric mapping was used to identify the between-group differences in magnitude of asymmetry of performance and biomechanical variables. Results: There were differences in asymmetry of biomechanical variables across all jump and CoD tests, with greater asymmetries in the ACLR group. The majority of differences between groups were in the sagittal and frontal planes, with more differences found in the jump than CoD tests. The single-legged drop jump demonstrated large differences in performance asymmetry (effect size, 0.94) with small differences for both CoD tests (0.4) and none for the single-legged hop for distance. Conclusion: This study demonstrated greater asymmetry of biomechanical variables 9 months after ACLR as compared with healthy participants across all tests, suggesting insufficient rehabilitation. Clinical Relevance: This study highlights the importance of including biomechanical as well as performance variables when assessing rehabilitation status after ACLR. Registration: NCT02771548 ( ClinicalTrials.gov identifier).

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Dudley, R., et P. Chai. « Animal flight mechanics in physically variable gas mixtures ». Journal of Experimental Biology 199, n^o 9 (1 septembre 1996) : 1881–85. http://dx.doi.org/10.1242/jeb.199.9.1881.

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Empirical studies of animal flight performance have generally been implemented within the contemporary atmosphere. Experimental alteration of the physical composition of gas mixtures, however, permits construction of novel flight media and the non-invasive manipulation of flight biomechanics. For example, replacement of atmospheric nitrogen with various noble gases results in a tenfold variation in air density at a constant oxygen concentration. Such variation in air density correspondingly elicits extraordinary biomechanical effort from flying animals; hummingbirds and euglossine orchid bees hovering in such low-density but normoxic mixtures have demonstrated exceptionally high values for the mechanical power output of aerobic flight muscle. As with mechanical power, lift coefficients during hovering increase at low air densities in spite of a concomitant decline in the Reynolds number of the wings. The physical effects of variable gas density may also be manifest in morphological and physiological adaptations of animals to flight across altitudinal gradients. Global variation in atmospheric composition during the late Paleozoic may also have influenced the initial evolution and subsequent diversification of ancestral pterygotes. For the present-day experimenter, the use of physically variable flight media represents a versatile opportunity to explore the range of kinematic and aerodynamic modulation available to flying animals.

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Post, Andrew, T. Blaine Hoshizaki, Roger Zemek, Michael D. Gilchrist, David Koncan, Lauren Dawson, Wesley Chen, Andrée-Anne Ledoux et _. _. « Pediatric concussion : biomechanical differences between outcomes of transient and persistent (> ; 4 weeks) postconcussion symptoms ». Journal of Neurosurgery : Pediatrics 19, n^o 6 (juin 2017) : 641–51. http://dx.doi.org/10.3171/2016.11.peds16383.

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OBJECTIVECurrently, little is known about the biomechanics of head impact for concussion in youths (ages 5 to 18 years). Even less is known about the biomechanical characteristics and variables related to head impacts that may be useful in differentiating between transient and persistent postconcussion symptoms in a youth population. The purpose of this research was to examine the differences in biomechanics of youth head impact for transient postconcussion symptoms (TPCSs) and persistent postconcussion symptoms (PPCSs) by using data from a hospital population.METHODSIn a laboratory setting and using physical, computational, and finite element models, the authors reconstructed falling events in a large cohort of patients who had sustained a brain injury that resulted in transient or persistent postconcussion symptoms. The falling events and resulting concussions for the TPCS and PPCS patient groups were analyzed in terms of force, energy, peak resultant linear and rotational accelerations, and maximum principal strain in the gray and white matter of the brain, as well as measurements of cumulative strain damage.RESULTSThe results indicated that there were no significant differences between the groups for any of the variables analyzed.CONCLUSIONSWith methods derived for use in an adult population, the magnitudes of peak linear acceleration for the youth data set were determined to be above the 50% risk of injury. The youth data set showed higher brain tissue strain responses for lower energy and impact velocities than measured in adults, suggesting that youths are at higher risk of concussive injury at lower event severities. A trend shown by some variables indicated that larger magnitudes of response were associated with PPCSs, but no single measurement variable consistently differentiated between the TPCS and PPCS groups. It is possible that using the biomechanics of head and brain responses to predict a subjective symptom load may not be appropriate. To enhance future biomechanical analyses, further investigations should include the use of quantifiable measures of brain injury linked to clinical outcomes and possible confounding factors such as history of brain injury and patient predisposition.

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Bronson, Dwight G., Mikhail L. Samchukov, John G. Birch, Richard H. Browne et Richard B. Ashman. « Stability of external circular fixation : a multi-variable biomechanical analysis ». Clinical Biomechanics 13, n^o 6 (septembre 1998) : 441–48. http://dx.doi.org/10.1016/s0268-0033(98)00007-2.

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Atiković, Almir. « New Regression Models to Evaluate the Relationship between Biomechanics of Gymnastic Vault and Initial Vault Difficulty Values ». Journal of Human Kinetics 35, n^o 1 (1 décembre 2012) : 119–26. http://dx.doi.org/10.2478/v10078-012-0085-6.

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The main objective of this paper was to determine the relationship between biomechanical parameters of vault flights with respect to new models of initial vault difficulty values in men’s artistic gymnastic. The study sample included vaults (n=64) and models (n=5) from the 2009 Code of Points (CoP) of the Federation International of Gymnastics (FIG). The dependent variable included all difficulty values ranging from 2-7.2 points, while the sample of independent variables included twelve biomechanical parameters. After implementing the regression analysis, it could be established that the best model derived only the second flight phase with 95% of explained variance.

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Leite, Isaura, Pedro Fonseca, Lurdes Ávila-Carvalho, João Paulo Vilas-Boas, Márcio Goethel, Luis Mochizuki et Filipe Conceição. « Biomechanical Research Methods Used in Acrobatic Gymnastics : A Systematic Review ». Biomechanics 3, n^o 1 (10 janvier 2023) : 52–68. http://dx.doi.org/10.3390/biomechanics3010005.

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The biomechanical analysis of Acrobatic Gymnastics elements has not been extensively explored in scientific research to date. Due to the increased challenge of implementing experimental protocols and collecting data from multiple individuals, it is required to develop strategies that allow a safe, valid and reproducible methodology. This work aims to collect information and systematically analyze the biomechanical approach in Acrobatic Gymnastics to date. A search was conducted in the Web of Science, Scopus, EBSCO, PubMed and ISBS databases. After the selection and quality-control phases, fourteen documents were included. The results revealed that the biomechanical research in Acrobatics has been focused on balance evaluation, in which the force plate and the center of pressure are the most used instrument and variable, respectively. Research has been focused on kinetics evaluation. Kinematics analysis of pair/group elements would provide scientific answers to unresolved problems, considering that Gymnastics provides almost limitless possibilities to study human motion. Researchers should focus on the type of element, difficulty degree, main characteristics, relationship between the instrument and floor surface specificity and safety conditions. We encourage gymnastics clubs and coaches to establish networks with biomechanics laboratories, allowing to bridge the gap between research and practice.

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Gefen, Amit. « Mathematical Functions and Their Properties as Relevant to the Biomechanical Modeling of Cell and Tissue Damage ». Journal of Applied Biomechanics 26, n^o 1 (février 2010) : 93–103. http://dx.doi.org/10.1123/jab.26.1.93.

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The extrapolation of biological damage from a biomechanical model requires that a closed-form mathematical damage threshold function (DTF) be included in the model. A DTF typically includes a generic load variable, being the critical load (e.g., pressure, strain, temperature) causing irreversible tissue or cell damage, and a generic time variable, which represents the exposure to the load (e.g., duration, strain rate). Despite the central role that DTFs play in biomechanical studies, there is no coherent literature on how to formulate a DTF, excluding the field of heat-induced damage studies. This technical note describes six mathematical function types (Richards, Boltzmann, Morgan-Mercer-Flodin, Gompertz, Weibull, Bertalanffy) that are suitable for formulating a wide range of DTFs. These functions were adapted from the theory of restricted growth, and were fitted herein to describe biomechanical damage phenomena. Relevant properties of each adapted function type were extracted to allow efficient fitting of its parameters to empirical biomechanical data, and some practical examples are provided.

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Wang, Nenzi, et Yen-Hsiu Liu. « Application of Taguchi's Design of Experiments to the Study of Biomechanical Systems ». Journal of Applied Biomechanics 20, n^o 3 (août 2004) : 219–29. http://dx.doi.org/10.1123/jab.20.3.219.

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An efficient global optimization procedure is presented by using Taguchi's design of experiments (TDE) as a means for undertaking biomechanical studies that rely on experimentations. The proposed TDE is a systematic method of fractional factorial designs for conducting experiments with many independent variables. The approach can provide a step-by-step means for predicting the results of a comparative full factorial design only with a small number of tests. In this study a three-level, four-variable heel-toe running model, and a two-level, seven-variable bicycle example were examined to show the capability and robustness of TDE. In the process of the analysis, the orthogonal array and signal-to-noise ratio analysis of TDE were used to set up the trial conditions and analyze the results. It is shown that in the heel-toe running analyses the TDE successfully predicted the optimum sets of variables with 89% fewer trials than the full factorial design. The reduction in number of trials in the bicycle example is 94%. As a result, the use of TDE analysis to replace a full factorial analysis can considerably reduce the number of trials and still provide a useful outcome in many multifactor biomechanical studies.

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Borisov, Andrey V., et Konstantin D. Filippenkov. « Controlling a Variable-Length Exoskeleton Link ». Vestnik MEI 3, n^o 3 (2021) : 110–20. http://dx.doi.org/10.24160/1993-6982-2021-3-110-120.

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The aim of the study is to develop a spatial electromechanical model of a variable-length link for use in telescopic manipulators, anthropomorphic robots, exoskeletons, and in studying the human musculoskeletal system. The proposed link model has two massive absolutely solid sections at the ends and a weightless section of variable length located between them. The study was carried out using the methods of theoretical mechanics, electromechanics, mathematical modeling, engineering design, numerical methods for solving systems of ordinary differential equations, control theory, nonlinear dynamics, experimental methods, and empirical data on the biomechanical properties of the human musculoskeletal system. The reliability of the obtained results is substantiated by a rigorous use of the above-mentioned methods. As a result of the study, a system of Lagrange-Maxwell differential equations was written, and an electromechanical model of an anthropomorphic system was developed in the Matlab Simulink software package. With the specified geometric and inertial parameters of a variable-length link corresponding to an average person's leg lower part and the time corresponding to the single-support motion phase, the electric motors and reducing gears implementing the human musculoskeletal system link's biomechanical motion fragment are selected. All of the selected motors have a sufficient operating parameters margin. The trajectories of all generalized coordinates along which the anthropomorphic system performs its necessary motion are determined. The mechanism load diagrams are obtained. The control system for the motors is synthesized, and the positioning error is evaluated. The novelty of the approach is that the newly developed electromechanical models of controlled variable-length links have a wide range of applying the obtained results and can be used in designing anthropomorphic robots and comfortable new-generation exoskeletons. Thus, the electromechanical model of a variable-length link with the parameters corresponding to the average person's leg lower part has been developed. The electric drives and transmissions able to implement a motion close to the anthropomorphic one have been selected; its implementation has been demonstrated, and the numerical calculation results are given.

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Sanderson, David J. « An Application of a Computer Based Real-Time Data Acquisition and Feedback System ». International Journal of Sport Biomechanics 2, n^o 3 (août 1986) : 210–14. http://dx.doi.org/10.1123/ijsb.2.3.210.

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The purpose of this experiment was to assess the efficacy of using real-time generated computer feedback of a selected biomechanical variable, force, for modifying the pattern-of-force application of inexperienced cyclists while they cycled at a steady rate (60 rpm) and power output (approximately 112 watts). Positive results would imply that the technique of using biomechanical variables as augmented feedback could be applied in a learning study in such a way to train for the enhancement of performance of cyclists. This approach differs from the traditional one of using novices performing novel tasks. Even though the cyclists were inexperienced, they nonetheless knew how to cycle and thus modifications of the pattern of force application were made to an already existing complex skill.

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Watson, M. A., K. J. Mathias et N. Maffulli. « External ring fixators : An overview ». Proceedings of the Institution of Mechanical Engineers, Part H : Journal of Engineering in Medicine 214, n^o 5 (1 mai 2000) : 459–70. http://dx.doi.org/10.1243/0954411001535480.

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External fixation is widely used in the fixation of fractures and limb deformities. The mechanical characteristics of a specific external fixator are major factors in determining the biomechanical environment at a fracture/osteotomy site and, hence, affect the healing process. Although the optimal biomechanical environment for healing of a fracture or an osteotomy is unknown, a specific range of interfragmentary motion exists which promotes healing. It is therefore desirable that the mechanics of an external fixator can be manipulated to enable the surgeon to control the range of interfragmentary motion. The characteristics of an external fixator are defined by a large number of variables. Therefore, to gain control over the degree of interfragmentary motion, an understanding of the effect of each variable and how it interacts with the others to determine the overall characteristics of the device is required. For the past two decades, individual components and whole-frame configurations have been studied in depth. This article provides a summary of previous work concerning the mechanics of external ring fixators and how they affect the biomechanical environment at the fracture/osteotomy site.

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Bergamini, Elena, Francesca Morelli, Flavia Marchetti, Giuseppe Vannozzi, Lorenzo Polidori, Francesco Paradisi, Marco Traballesi, Aurelio Cappozzo et Anna Sofia Delussu. « Wheelchair Propulsion Biomechanics in Junior Basketball Players : A Method for the Evaluation of the Efficacy of a Specific Training Program ». BioMed Research International 2015 (2015) : 1–10. http://dx.doi.org/10.1155/2015/275965.

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As participation in wheelchair sports increases, the need of quantitative assessment of biomechanical performance indicators and of sports- and population-specific training protocols has become central. The present study focuses on junior wheelchair basketball and aims at (i) proposing a method to identify biomechanical performance indicators of wheelchair propulsion using an instrumented in-field test and (ii) developing a training program specific for the considered population and assessing its efficacy using the proposed method. Twelve athletes (10 M, 2 F, age = 17.1 ± 2.7 years, years of practice = 4.5 ± 1.8) equipped with wheelchair- and wrist-mounted inertial sensors performed a 20-metre sprint test. Biomechanical parameters related to propulsion timing, progression force, and coordination were estimated from the measured accelerations and used in a regression model where the time to complete the test was set as dependent variable. Force- and coordination-related parameters accounted for 80% of the dependent variable variance. Based on these results, a training program was designed and administered for three months to six of the athletes (the others acting as control group). The biomechanical indicators proved to be effective in providing additional information about the wheelchair propulsion technique with respect to the final test outcome and demonstrated the efficacy of the developed program.

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Rusdiana, Agus, Herman Subarjah, Iman Imanudin, Yopi Kusdinar, Angga M Syahid et Tian Kurniawan. « Effect of Fatigue on Biomechanical Variable Changes in Overhead Badminton Jump Smash ». Annals of Applied Sport Science 8, n^o 3 (1 octobre 2020) : 0. http://dx.doi.org/10.29252/aassjournal.895.

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Borisov, Andrey V., et Blinov AO. « Displacement energy of the two variable-length element biomechanical exoskeleton supporting leg ». International Journal of Biosensors & ; Bioelectronics 7, n^o 4 (23 septembre 2021) : 113–14. http://dx.doi.org/10.15406/ijbsbe.2021.07.00223.

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The article discusses a spatial model of two links of variable length of an active biomedical exoskeleton that simulate a supporting leg. Each hinge has drives that provide the necessary turns with the relative rotational movement of the links. The difference between the proposed model and those previously studied is the use of the angles between the links, which corresponds to the real operation of the drives. The paths of the links are set kinematically. The control forces are determined in the model from the compiled system of differential equations of motion. The calculation of energy consumption during the single-support phase of movement for one step is carried out. The application of the proposed model in the form of two links of variable length of the active biomedical exoskeleton can be found when selecting a battery for the autonomous operation of the biomedical exoskeleton.

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Porojan, Liliana, Florin Topală et Sorin Porojan. « Biomechanical Behavior of All-Ceramic Crowns with Variable Thicknesses of Zirconia Frameworks ». Applied Mechanics and Materials 835 (mai 2016) : 97–102. http://dx.doi.org/10.4028/www.scientific.net/amm.835.97.

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Zirconia is an extremely successful material for prosthetic restorations, offering attractive mechanical and optical properties. It offers several advantages for posterior restorations because it can withstand physiological posterior forces. The aim of the study was to achieve the influence of zirconia framework thickness on the mechanical behavior of all-ceramic crowns using numerical simulation. For the study a premolar was chosen in order to simulate the mechanical behavior in the components of all-ceramic crowns and teeth structures regarding to the zirconia framework thickness. Maximal Von Mises equivalent stress values were recorded in teeth and restorations. Due to the registered maximal stress values it can be concluded that it is indicated to achieve frameworks of at least 0.5 mm thickness in the premolar area. Regarding stress distribution concentration were observed in the veneer around the contact areas with the antagonists, in the framework under the functional cusp and in the oral part overall and in dentin around and under the marginal line, also oral. The biomechanical behavior of all ceramic crowns under static loads can be investigated by the finite element method.

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Youn, Ik-Hyun, Jong-Hoon Youn, Joseph Zeni et Brian Knarr. « Biomechanical Gait Variable Estimation Using Wearable Sensors after Unilateral Total Knee Arthroplasty ». Sensors 18, n^o 5 (15 mai 2018) : 1577. http://dx.doi.org/10.3390/s18051577.

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Goodyer, Eric, Frank Müller, Markus Hess, Karthikeyan Kandan et Farukh Farukh. « Biomechanical Flow Amplification Arising From the Variable Deformation of the Subglottic Mucosa ». Journal of Voice 31, n^o 6 (novembre 2017) : 669–74. http://dx.doi.org/10.1016/j.jvoice.2017.03.013.

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Zainab Shakir et Dr. Widad Kadhum. « The relationship of some physical variables and performance angles to the strength of the straight serve for junior tennis ». Modren Sport Journal 20, n^o 4 (29 décembre 2021) : 0061. http://dx.doi.org/10.54702/msj.2021.20.4.0061.

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The problem of the research in determining the appropriate angles in the strength of serve for tennis age (14-16) year according to the specific biomechanical conditions, and the extent of the relationship of each variable of the physical variables in the successful performance of the skill of serve, and achieving the strength of transmission for tennis age (14-16) year, and it is one of the biomechanical principles that can be used in evaluating the angles of body parts. age (14-16) year tennis players. The aim of the research is to identify the percentage of the contribution of some physical variables of the straight serve for tennis juniors, and the percentage of the contribution of some corners of the body to the strength of serve for the tennis age (14-16) year (18) players. The two researchers reached a number of results, the most important of which are: There is a statistically significant correlation between some physical abilities and body angles with the straight serve for tennis players. The lower the angles (elbow, shoulder, knee for the front leg) at the moment of hitting the tennis ball, the stronger the serve will be. Correlation relationship with some biomechanical variables, because the skill of serve requires the strength of the striking arm during the performance of the straight serve

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Giacomozzi, Claudia, Giada Lullini, Alberto Leardini, Paolo Caravaggi, Maurizio Ortolani, Giulio Marchesini, Luca Baccolini et Lisa Berti. « Analysis of Clinical Profiles, Deformities, and Plantar Pressure Patterns in Diabetic Foot Syndrome ». Applied Sciences 11, n^o 23 (3 décembre 2021) : 11464. http://dx.doi.org/10.3390/app112311464.

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Diabetic foot syndrome refers to heterogeneous clinical and biomechanical profiles, which render predictive models unsatisfactory. A valuable contribution may derive from identification and descriptive analysis of well-defined subgroups of patients. Clinics, biology, function, gait analysis, and plantar pressure variables were assessed in 78 patients with diabetes. In 15 of them, the 3D architecture of the foot bones was characterized by using weight-bearing CT. Patients were grouped by diabetes type (T1, T2), presence (DN) or absence (DNN) of neuropathy, and obesity. Glycated hemoglobin (HbA1c) and plantar lesions were monitored during a 48-month follow-up. Statistical analysis showed significant differences between the groups for at least one clinical (combined neuropathy score, disease duration, HbA1c), biological (age, BMI), functional (joint mobility, foot alignment), or biomechanical (regional peak pressure, pressure-time integral, cadence, velocity) variable. Twelve patients ulcerated during follow-up (22 lesions in total), distributed in all groups but not in the DNN T2 non-obese group. These showed biomechanical alterations, not always occurring at the site of lesion, and HbA1c and neuropathy scores higher than the expected range. Three of them, who also had weight-bearing CT analysis, showed >40% of architecture parameters outside the 95%CI. Appropriate grouping and profiling of patients based on multi-instrumental clinical and biomechanical analysis may help improve prediction modelling and management of diabetic foot syndrome.

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Guimarães, Eduardo S., Artur A. Sá, Rafael C. Soares, Paulo Felipe R. Bandeira, Helena Moreira, Jaqueliny R. S. Guimarães, Francisco do Ó. de Lima Júnior et Ronaldo C. D. Gabriel. « Classification of the Effort Index and Biomechanical Overload in Natural Trails of UNESCO Global Geoparks—A Network Perspective of Trails of the Araripe UGG (NE Brazil) ». International Journal of Environmental Research and Public Health 19, n^o 21 (1 novembre 2022) : 14297. http://dx.doi.org/10.3390/ijerph192114297.

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Natural trails in UNESCO Global Geopark territories show strong salutogenic, inclusive and interactive characteristics as potentials and opportunities for ecosystem health. It is essential to provide information to inform the hiker as to the characteristics of the environment and the attractions and challenges of the route. Based on a network analysis methodology we aimed to identify the indicators of centrality and strength of connection in order to classify the effort index and biomechanical overload of the Araripe UNESCO Global Geopark trails in Brazil. The results showed strong connection and centrality of the variables related to the biomechanical overload in the effort index. In the trail of Pontal de Cruz the altimetric variation and the surface of the ground are highlighted in the biomechanical overload that presented a horizontal course equivalent 2.6 times larger than the presented distance. In Sítio Fundão trail, the surface of the ground also stood out, increasing the exposure in 36% of the presented distance. On the Missão Velha Waterfall trail, the variable that stood out was the biomechanical overload on the knee, equivalent to a horizontal increase of 28% of the measured distance. The methodology presented sought to optimise the mapping, management and consolidation of a network of natural trails aggregated to a high geotouristic, scientific, educational, cultural and well-being potential as presented in the Araripe UGG territory.

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Candela-Leal, Milton Osiel, Erick Adrián Gutiérrez-Flores, Gerardo Presbítero-Espinosa, Akshay Sujatha-Ravindran, Ricardo Ambrocio Ramírez-Mendoza, Jorge de Jesús Lozoya-Santos et Mauricio Adolfo Ramírez-Moreno. « Multi-Output Sequential Deep Learning Model for Athlete Force Prediction on a Treadmill Using 3D Markers ». Applied Sciences 12, n^o 11 (27 mai 2022) : 5424. http://dx.doi.org/10.3390/app12115424.

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Reliable and innovative methods for estimating forces are critical aspects of biomechanical sports research. Using them, athletes can improve their performance and technique and reduce the possibility of fractures and other injuries. For this purpose, throughout this project, we proceeded to research the use of video in biomechanics. To refine this method, we propose an RNN trained on a biomechanical dataset of regular runners that measures both kinematics and kinetics. The model will allow analyzing, extracting, and drawing conclusions about continuous variable predictions through the body. It marks different anatomical and reflective points (96 in total, 32 per dimension) that will allow the prediction of forces (N) in three dimensions (Fx, Fy, Fz), measured on a treadmill with a force plate at different velocities (2.5 m/s, 3.5 m/s, 4.5 m/s). In order to obtain the best model, a grid search of different parameters that combined various types of layers (Simple, GRU, LSTM), loss functions (MAE, MSE, MSLE), and sampling techniques (down-sampling, up-sampling) helped obtain the best performing model (LSTM, MSE, down-sampling) achieved an average coefficient of determination of 0.68, although when excluding Fz it reached 0.92.

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Seebacher, Frank, et Rob S. James. « Plasticity of muscle function in a thermoregulating ectotherm (Crocodylus porosus) : biomechanics and metabolism ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 294, n^o 3 (mars 2008) : R1024—R1032. http://dx.doi.org/10.1152/ajpregu.00755.2007.

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Thermoregulation and thermal sensitivity of performance are thought to have coevolved so that performance is optimized within the selected body temperature range. However, locomotor performance in thermoregulating crocodiles ( Crocodylus porosus) is plastic and maxima shift to different selected body temperatures in different thermal environments. Here we test the hypothesis that muscle metabolic and biomechanical parameters are optimized at the body temperatures selected in different thermal environments. Hence, we related indices of anaerobic (lactate dehydrogenase) and aerobic (cytochrome c oxidase) metabolic capacities and myofibrillar ATPase activity to the biomechanics of isometric and work loop caudofemoralis muscle function. Maximal isometric stress (force per muscle cross-sectional area) did not change with thermal acclimation, but muscle work loop power output increased with cold acclimation as a result of shorter activation and relaxation times. The thermal sensitivity of myofibrillar ATPase activity decreased with cold acclimation in caudofemoralis muscle. Neither aerobic nor anaerobic metabolic capacities were directly linked to changes in muscle performance during thermal acclimation, although there was a negative relationship between anaerobic capacity and isometric twitch stress in cold-acclimated animals. We conclude that by combining thermoregulation with plasticity in biomechanical function, crocodiles maximize performance in environments with highly variable thermal properties.

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Jorgensen, Michael J., William S. Marras et Thomas R. Waters. « The Effect of a Variable Lumbar Erector Spinae Sagittal Plane Moment Arm on Predicted Spinal Loading ». Proceedings of the Human Factors and Ergonomics Society Annual Meeting 46, n^o 13 (septembre 2002) : 1061–65. http://dx.doi.org/10.1177/154193120204601312.

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Recent research indicates that the sagittal plane moment arm of the erector spinae decreases at the L5/S1 level during torso flexion. The objective of this study was to assess the predicted L5/S1 spinal loading from a lifting task when allowing the erector spinae sagittal plane moment arm to vary during torso flexion. Nineteen male subjects lifted three loads from two origin locations to an upright neutral posture. Spinal loading was predicted from an EMG-assisted biomechanical model that allowed the erector spinae moment arm to vary during torso flexion. The predicted lateral, anterior-posterior shear and compression forces increased by 7.4%, 11.1% and 6.6%, respectively, when compared to using a biomechanical model that kept the erector spinae moment arm constant. These results suggest that models that account for the varying erector spinae moment arm predict greater spinal loads, especially for motions that involve a large degree of torso flexion.

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Ciszkiewicz, Adam. « Analyzing Uncertainty of an Ankle Joint Model with Genetic Algorithm ». Materials 13, n^o 5 (6 mars 2020) : 1175. http://dx.doi.org/10.3390/ma13051175.

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Recent studies in biomechanical modeling suggest a paradigm shift, in which the parameters of biomechanical models would no longer treated as fixed values but as random variables with, often unknown, distributions. In turn, novel and efficient numerical methods will be required to handle such complicated modeling problems. The main aim of this study was to introduce and verify genetic algorithm for analyzing uncertainty in biomechanical modeling. The idea of the method was to encode two adversarial models within one decision variable vector. These structures would then be concurrently optimized with the objective being the maximization of the difference between their outputs. The approach, albeit expensive numerically, offered a general formulation of the uncertainty analysis, which did not constrain the search space. The second aim of the study was to apply the proposed procedure to analyze the uncertainty of an ankle joint model with 43 parameters and flexible links. The bounds on geometrical and material parameters of the model were set to 0.50 mm and 5.00% respectively. The results obtained from the analysis were unexpected. The two obtained adversarial structures were almost visually indistinguishable and differed up to 38.52% in their angular displacements.

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Roemer, Karen, Tibor Hortobagyi, Chris Richter, Yolanda Munoz-Maldonado et Stephanie Hamilton. « Effect of BMI on Knee Joint Torques in Ergometer Rowing ». Journal of Applied Biomechanics 29, n^o 6 (décembre 2013) : 763–68. http://dx.doi.org/10.1123/jab.29.6.763.

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Although an authoritative panel recommended the use of ergometer rowing as a non-weight-bearing form of exercise for obese adults, the biomechanical characterization of ergometer rowing is strikingly absent. We examined the interaction between body mass index (BMI) relative to the lower extremity biomechanics during rowing in 10 normal weight (BMI 18–25), 10 overweight (BMI 25–30 kg·m−2), and 10 obese (BMI > 30 kg·m−2) participants. The results showed that BMI affects joint kinematics and primarily knee joint kinetics. The data revealed that high BMI leads to unfavorable knee joint torques, implying increased loads of the medial compartment in the knee joint that could be avoided by allowing more variable foot positioning on future designs of rowing ergometers.

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Quigley, Kevin J., Dirk H. Alander et John Gary Bledsoe. « An In Vitro Biomechanical Investigation : Variable Positioning of Leopard Carbon Fiber Interbody Cages ». Journal of Spinal Disorders & ; Techniques 21, n^o 6 (août 2008) : 442–47. http://dx.doi.org/10.1097/bsd.0b013e3181568637.

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Teoh, Jee Chin, et Taeyong Lee. « Biomechanical effects of variable stiffness shoes in normal walking after 60-minute adaptation ». Footwear Science 9, sup1 (10 mai 2017) : S146—S147. http://dx.doi.org/10.1080/19424280.2017.1314386.

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Wee, Jaeyeon, Jee Chin Teoh et Taeyong Lee. « Biomechanical Effects of Variable Stiffness Shoes in Normal Walking After 60-minute Adaptation ». International Journal of Precision Engineering and Manufacturing 20, n^o 10 (9 septembre 2019) : 1817–23. http://dx.doi.org/10.1007/s12541-019-00216-8.

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Brailovski, Vladimir, Yann Facchinello, Martin Brummund, Yvan Petit et Jean-Marc Mac-Thiong. « Ti–Ni Rods with Variable Stiffness for Spine Stabilization : Manufacture and Biomechanical Evaluation ». Shape Memory and Superelasticity 2, n^o 1 (24 février 2016) : 3–11. http://dx.doi.org/10.1007/s40830-016-0053-4.

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Melling, Mahmoud, Roland Reihsner, Martin Steindl, Daniela Karimian-Teherani, Martina Schnallinger et Mark Behnam. « Biomechanical stability of abductor pollicis longus muscles with variable numbers of tendinous insertions ». Anatomical Record 250, n^o 4 (avril 1998) : 475–79. http://dx.doi.org/10.1002/(sici)1097-0185(199804)250:4<475 ::aid-ar11>3.0.co;2-l.

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Grant, Jonathan R., John S. Rhee, Frank A. Pintar et Narayan Yoganandan. « Modeling Mechanisms of Skull Base Injury for Drivers in Motor Vehicle Collisions ». Otolaryngology–Head and Neck Surgery 137, n^o 2 (août 2007) : 195–200. http://dx.doi.org/10.1016/j.otohns.2007.04.005.

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OBJECTIVE: To develop biomechanical variable models for driver skull base injury mechanisms in motor vehicle collisions. STUDY DESIGN: Retrospective database review. METHODS: Biomechanical collision variables and safety restraint data were analyzed for Crash Injury Research and Engineering Network skull base trauma subjects enrolled during the recruitment period between 1996 and 2005. RESULTS: For drivers satisfying inclusion criteria (n = 26), injury resulted from contact with rigid vehicle structural elements in 82%, and occurred in 50% despite both seatbelt and air bags. Eight percent used neither seatbelts nor air bags. Seventy-two percent involved vector velocity changes greater than 30 mph. The relative morbidity of skull base injuries was also detailed. CONCLUSION: The majority of driver skull base injuries resulted from contact with rigid vehicle structural elements in high velocity crashes. Seatbelt and air bag use could not be definitively correlated with skull base injury. CLINICAL SIGNIFICANCE: Injury mechanism models can be developed that facilitate further investigations to determine impact and scope on a national scale.

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Denard, Patrick J., Christopher R. Adams, Nicole C. Fischer, Marina Piepenbrink et Coen A. Wijdicks. « Knotless Fixation Is Stronger and Less Variable Than Knotted Constructs in Securing a Suture Loop ». Orthopaedic Journal of Sports Medicine 6, n^o 5 (1 mai 2018) : 232596711877400. http://dx.doi.org/10.1177/2325967118774000.

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Background: Historically, tendon-to-bone fixation has relied on knot tying. However, considerable variability exists in knot-tying strength among surgeons. Purpose/Hypothesis: The purpose of this study was to compare the biomechanical properties of knotted and knotless fixation and to evaluate variability among surgeons. The hypothesis was that knotless constructs would be stronger and have less variability as compared with knotted constructs. Study Design: Controlled laboratory study. Methods: A total of 34 orthopaedic surgeons participated in a laboratory study to compare knotted and knotless constructs, where 104 knotted constructs were performed with No. 2 suture, 21 knotless constructs with No. 2 suture (K2 group), and 79 knotless constructs with suture tape (KT group). Mechanical testing was performed to compare load at 3 mm of displacement, load to failure, and stiffness of each construct. Results: The mean load at 3 mm of displacement was greatest in the KT group, with significant differences among all 3 groups ( P < .001). Load to failure was significantly greater in the KT group as compared with the K2 group and the knotted group ( P < .001), but there was no difference between the K2 and knotted groups ( P ≥ .999). Stiffness and displacement were also greatest in the KT group. Based on the F test, the variance in load to failure was significantly different between the knotted and knotless constructs, with the knotted group demonstrating greater variability (SD, 94 N) than the KT (SD, 38 N) and K2 (SD, 17 N) groups ( P < .001). Conclusion: Knotless fixation with suture tape had improved biomechanical performance as compared with knots or knotless fixation with No. 2 suture. In addition, knotless fixation had less variability in biomechanical properties among multiple surgeons. Clinical Relevance: This study may be relevant for surgeons choosing between knotted and knotless constructs as well as for considerations in the design of rotator cuff repair constructs.

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Broshko, Ye O. « Variability of Structural and Biomechanical Parameters of Pelophylax Esculentus (Amphibia, Anura) Limb Bones ». Vestnik Zoologii 48, n^o 3 (17 juillet 2014) : 239–48. http://dx.doi.org/10.2478/vzoo-2014-0027.

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Abstract Variability of Structural and Biomechanical Prameters of Pelophylax esculentus (Amphibia, Anura) Limb Bones. Broshko Ye. O. — Structural and biomechanical parameters of Edible Frog, Pelophylax esculentus (Linnaeus, 1758), limb bones, namely, mass, linear dimensions, parameters of the shaft’s cross-sectional shape (cross-sectional area, moments of inertia, radiuses of inertia) were investigated. Some coefficients were also estimated: diameters ratio (df/ds), cross-sectional index (ik), principal moments of inertia ratio (Imax/Imin.). Coefficients of variation of linear dimensions (11.9-20.0 %) anrelative bone mass (22-35 %) were established. Moments of inertia of various bones are more variable (CV = 41.67-56.35 %) in relation to radii of inertia (CV = 9.68-14.67 %). Shaft’s cross-sectional shape is invariable in all cases. However, there is high individual variability of structural and biomechanical parameters of P. esculentus limb bones. Variability of parameters was limited by the certain range. We suggest the presence of stable norm in bone structure. Stylopodium bones have the primary biomechanical function among the elements of limb skeleton, because their parameters most clearly responsive to changes in body mass.

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Spiker, John C., et Denise L. Massie. « Comprehensive Management of Patellofemoral Pain ». Journal of Sport Rehabilitation 1, n^o 3 (août 1992) : 258–63. http://dx.doi.org/10.1123/jsr.1.3.258.

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Effective management of patellofemoral pain is challenging to the practitioner when attempting to maintain the athlete's desired activity level while minimizing the symptoms. Due to the numerous etiological factors behind anterior knee pain, comprehensive management must include a lower extremity evaluation of muscular flexibility and strength as well as biomechanical abnormalities. Rehabilitation programs must focus on the flexibility, strength, endurance and proprioception of the extremity while reducing abnormal biomechanical forces. Programs to treat these abnormalities that increase patellofemoral stress must be systematically upgraded one variable at a time while monitoring the symptoms on a daily basis.

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Derby, Hunter, Harish Chander, Sachini N. K. Kodithuwakku Arachchige, Alana J. Turner, Adam C. Knight, Reuben Burch, Charles Freeman, Chip Wade et John C. Garner. « Occupational Footwear Design Influences Biomechanics and Physiology of Human Postural Control and Fall Risk ». Applied Sciences 13, n^o 1 (22 décembre 2022) : 116. http://dx.doi.org/10.3390/app13010116.

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While design modifications present on work boots improve safety, they may not always provide optimal human performance during work tasks. Understanding the impact of these different design features on biomechanical and physiological postural control and locomotion variables can aid in better design modifications that can provide a safe and efficient human performance. This brief review focuses on a series of studies conducted by the current research team, that have tested three different work boots (SB: high-top steel-toed work boots; TB: high-top tactical work boots; SR: low-top slip-resistant work boots). The series of studies included testing of these work boots or combinations of them under acute and chronic simulated occupational workloads, assessing biomechanical variable such as postural stability, gait, slips, and muscle activity, as well as physiological variables such as heart rate, energy expenditure, oxygen consumption, and pain perception. The impact of each of the work boots and their design feature on postural control and locomotion are summarized from these studies’ previously published literature. Finally, work boot design suggestions for optimal human performance are provided for better work boot selection, modification, and design.

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Bohl, Michael A., Sarah McBryan, Anna G. U. S. Newcomb, Jennifer N. Lehrman, Brian P. Kelly, Peter Nakaji, Steve W. Chang, Juan S. Uribe, Jay D. Turner et U. Kumar Kakarla. « Range of Motion Testing of a Novel 3D-Printed Synthetic Spine Model ». Global Spine Journal 10, n^o 4 (23 juin 2019) : 419–24. http://dx.doi.org/10.1177/2192568219858981.

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Study Design: Biomechanical model study. Objective: The Barrow Biomimetic Spine (BBS) project is a resident-driven effort to manufacture a synthetic spine model with high biomechanical fidelity to human tissue. The purpose of this study was to investigate the performance of the current generation of BBS models on biomechanical testing of range of motion (ROM) and axial compression and to compare the performance of these models to historical cadaveric data acquired using the same testing protocol. Methods: Six synthetic spine models comprising L3-5 segments were manufactured with variable soft-tissue densities and print orientations. Models underwent torque loading to a maximum of 7.5 N m. Torques were applied to the models in flexion-extension, lateral bending, axial rotation, and axial compression. Results were compared with historic cadaveric control data. Results: Each model demonstrated steadily decreasing ROM on flexion-extension testing with increasing density of the intervertebral discs and surrounding ligamentous structures. Vertically printed models demonstrated markedly less ROM than equivalent models printed horizontally at both L3-4 (5.0° vs 14.0°) and L4-5 (3.9° vs 15.2°). Models D and E demonstrated ROM values that bracketed the cadaveric controls at equivalent torque loads (7.5 N m). Conclusions: This study identified relevant variables that affect synthetic spine model ROM and compressibility, confirmed that the models perform predictably with changes in these print variables, and identified a set of model parameters that result in a synthetic model with overall ROM that approximates that of a cadaveric model. Future studies can be undertaken to refine model performance and determine intermodel variability.

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Articles de revues sur le sujet « Biomechanical variable »

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