\u3ci\u3eFairy\u3c/i\u3e and \u3ci\u3eElves\u3c/i\u3e in Tolkien and Traditional Literature

Explores the linguistic heritage of the terms elf and fairy, and shows how Tolkien eventually adapted them for his own purposes. Discusses the indistinguishable nature of early folkloric references to elves and dwarves, and how Tolkien picked out the characteristics he wished to use for his elves to suit the purposes of his stories

Cinemática de la flexión del tronco en postura sedente. Aproximación basada en el eje instantáneo de rotación

[EN] This PhD Thesis presents a research on trunk kinematics in seated posture, applied to defining a biomechanical model of the flexion-extension movement, and exploring the relationship between the trunk movement and the mechanisms of reclining work chairs. This research starts from a new way of characterizing human body movements. The proposed method uses a unified vector notation to analyze velocities as well as finite displacements. The main parameter was the instantaneous axis of rotation, which describes the geometric characteristics of movement, and may be used to interpret how body segments are joined. The analysis is based on explicit formulas, which allow a mathematical estimation of instrumental errors and controlling their size, which is critical in the calculation of the instantaneous axis. The trunk was modeled as a kinematic chain consisting of two rigid bodies (pelvis and thorax) that move relative to the seat. No restrictions were imposed on the movement beforehand, so that this free model let the movement describe itself. We conducted a series of experiments to validate the theory that supported the methodology, to quantify the errors that affected the measures, and to study the trunk movement in relation to a variety of office chairs. These experiments yielded a biomechanical model of trunk flexion in seated posture, that showed a rotation axis of the pelvis higher than former models, and a sequential rotation of lumbar vertebrae. We also studied experimentally the kinematics of reclining chairs mechanisms, and how they altered the movement of the thorax when subjects sat on them. The results of this research provide a new insight on human movement in general, and about seated posture in particular, and they also contribute to developing new ideas about the design of chairs and their relation to trunk mobility[ES] En esta tesis doctoral se presenta el desarrollo de una investigación sobre la cinemática del tronco en la postura sedente, aplicada a la definición de un modelo biomecánico del movimiento de flexo-extensión, y al estudio de la relación entre el movimiento del tronco y los mecanismos de reclinación de las sillas de trabajo. Esta investigación parte de una nueva forma de caracterizar los movimientos del cuerpo humano. Se ha utilizado una notación vectorial unificada para estudiar las velocidades y los desplazamientos finitos. El principal elemento de estudio ha sido el eje instantáneo de rotación, que describe las características geométricas del movimiento y sirve para interpretar cómo se encuentran articulados los segmentos corporales. El procedimiento de análisis se basa en fórmulas explícitas, que permiten una estimación matemática de los errores instrumentales y controlar su magnitud, aspecto crítico a la hora de calcular los ejes instantáneos de rotación. El tronco se ha modelado como una cadena cinemática formada por dos cuerpos rígidos (pelvis y tórax) que se mueven respecto al asiento. No se ha impuesto ningún tipo de restricción previa al modelo, dejándole libertad para que el movimiento se describiese a sí mismo. Se ha llevado a cabo una serie de experimentos para validar la teoría que da base a la metodología, cuantificar los errores que afectaban a las medidas, y estudiar el movimiento del tronco en relación con una serie de sillas de oficina. Se ha definido un modelo biomecánico de la flexión del tronco en la postura sedente sin respaldo, que presenta un eje de rotación de la pelvis más elevado que el de modelos previos y una rotación secuencial de las vértebras lumbares. Además se ha estudiado experimentalmente la cinemática de los mecanismos de sillas reclinables y cómo se altera el movimiento del tórax al sentarse en ellas. Los resultados obtenidos aportan una nueva visión sobre el movimiento humano en general y el de la postura sedente en particular, y también contribuyen al desarrollo de nuevas ideas sobre el diseño de sillas y su relación con la movilidad del tronco.[CA] En aquesta tesi doctoral es presenta el desenvolupament d’una investigació sobre la cinemàtica del tronc en la postura sedent, aplicada a la definició d’un model biomecànic del moviment de flexo-extensió, i a l’estudi de la relació entre el moviment del tronc i els mecanismes de reclinació de les cadires de treball. Aquesta investigació parteix d’una nova forma de caracteritzar els moviments del cos humà. S’ha utilitzat una notació vectorial unificada per a estudiar les velocitats i els desplaçaments finits. El principal element d’estudi ha estat l’eix instantani de rotació, que descriu les característiques geomètriques del moviment i serveix per a interpretar com es troben articulats els segments corporals. El procediment d’anàlisi es basa en fórmules explícites, que permeteixen una estimació matemàtica dels errors instrumentals i controlar la seva magnitud, aspecte crític a l’hora de calcular els eixos instantanis de rotació. El tronc s’ha modelat com una cadena cinemàtica formada per dos cossos rígids (pelvis i tòrax) que es mouen respecte al seient. No s’ha imposat cap tipus de restricció prèvia al model, deixant llibertat per a que el moviment es descriga a si mateix. S’ha dut a terme una sèrie d’experiments per a validar la teoria que dóna base a la metodologia, quantificar els errors que afectaven a les mesures, i estudiar el moviment del tronc en relació amb una sèrie de cadires d’oficina. S’ha definit un model biomecànic de la flexió del tronc en la postura sedent sense respatller, que presenta un eix de rotació de la pelvis més elevat que el considerat per models previs i una rotació seqüencial de les vèrtebres lumbars. A més s’ha estudiat experimentalment la cinemàtica dels mecanismes de cadires reclinables i com s’altera el moviment del tòrax al seure-hi. Els resultats obtinguts aporten una nueva visió sobre el moviment humà en general i el de la postura sedent en particular, i també contribueixen al desenvolupament de noves idees sobre el disseny de cadires i la seva relació amb la mobilitat del tronc.A los Planes Nacionales de I+D coordinados entre la UPV y el IBV, Nuevos Modelos Biomecánicos Basados en Sistemas No Paramétricos (DPI2003-07883-C02-02), Generación de Criterios para el Desarrollo de Modelos Biomecánicos Articulares a partir de Datos Antropométricos Funcionales (DPI2006-14722-C02-02) y Modelado cinemático y dinámico del movimiento de los tejidos blandos (DPI2009-13830-C02-02). Son éstos los proyectos que han dado la oportunidad de llevar a cabo la investigación, y han facilitado el intercambio de conocimientos en análisis de mecanismos y en biomecánica, necesario para el éxito del trabajo.De Rosario Martínez, H. (2010). Cinemática de la flexión del tronco en postura sedente. Aproximación basada en el eje instantáneo de rotación [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/142775TESI

Analysing interactions of fitted models

Abstract This vignette presents a brief review about the existing approaches for the post-hoc analysis of interactions in factorial experiments, and describes how to perform some of the cited calculations and tests with the functions of package phia in R. Those functions include the calculation and plotting of cell means, and testing simple effects, residual effects, and interaction contrasts, among other possibilities. They can be applied to linear and generalized linear models, with or without covariates, and to mixed or multivariate linear models for repeated measures experiments

Point of optimal kinematic error: Improvement of the instantaneous helical pivot method for locating centers of rotation

[EN] This paper proposes a variation of the instantaneous helical pivot technique for locating centers of rotation. The point of optimal kinematic error (POKE), which minimizes the velocity at the center of rotation, may be obtained by just adding a weighting factor equal to the square of angular velocity in Woltring's equation of the pivot of instantaneous helical axes (PIHA). Calculations are simplified with respect to the original method, since it is not necessary to make explicit calculations of the helical axis, and the effect of accidental errors is reduced. The improved performance of this method was validated by simulations based on a functional calibration task for the gleno-humeral joint center. Noisy data caused a systematic dislocation of the calculated center of rotation towards the center of the arm marker cluster. This error in PIHA could even exceed the effect of soft tissue artifacts associated to small and medium deformations, but it was successfully reduced by the POKE estimation.This work has been funded by the Spanish Government (Grants DPI2009-13830-C02-01, DPI2009-13830-CO2-02, DPI2010-20814-CO2-01, DPI2010-20814-CO2-02).De Rosario Martínez, H.; Page Del Pozo, AF.; Mata Amela, V. (2014). Point of optimal kinematic error: Improvement of the instantaneous helical pivot method for locating centers of rotation. Journal of Biomechanics. 47(7):1742-1747. doi:10.1016/j.jbiomech.2014.02.003S1742174747

Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation

[EN] The accurate location of the main axes of rotation (AoR) is a crucial step in many applications of human movement analysis. There are different formal methods to determine the direction and position of the AoR, whose performance varies across studies, depending on the pose and the source of errors. Most methods are based on minimizing squared differences between observed and modelled marker positions or rigid motion parameters, implicitly assuming independent and uncorrelated errors, but the largest error usually results from soft tissue artefacts (STA), which do not have such statistical properties and are not effectively cancelled out by such methods. However, with adequate methods it is possible to assume that STA only account for a small fraction of the observed motion and to obtain explicit formulas through differential analysis that relate STA components to the resulting errors in AoR parameters. In this paper such formulas are derived for three different functional calibration techniques (Geometric Fitting, mean Finite Helical Axis, and SARA), to explain why each technique behaves differently from the others, and to propose strategies to compensate for those errors. These techniques were tested with published data from a sit-to-stand activity, where the true axis was defined using bi-planar fluoroscopy. All the methods were able to estimate the direction of the AoR with an error of less than 5 degrees whereas there were errors in the location of the axis of 30-40 mm. Such location errors could be reduced to less than 17 mm by the methods based on equations that use rigid motion parameters (mean Finite Helical Axis, SARA) when the translation component was calculated using the three markers nearest to the axis. (C) 2017 Elsevier Ltd. All rights reserved.This work was funded by the Spanish Government and co-financed by EU FEDER funds (Grant DPI2013-44227-R). We would like to thank Prof. Tung-Wu Lu, Tsung-Yuan Tsai, Mei-Ying Kuo and Horn-Chaung Hsu from National Taiwan University for making the data from their studies available for further research on STA,, and Dr. Tecla Bonci from the Italian University of Sport and Movement 'Foro Italico' for providing the access to benchmark data.De Rosario Martínez, H.; Page Del Pozo, AF.; Besa Gonzálvez, AJ. (2017). Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation. Journal of Biomechanics. 62:60-67. https://doi.org/10.1016/j.jbiomech.2017.01.046S60676

The detection of malingering in whiplash-related injuries: a targeted literature review of the available strategies

[EN] Objective The present review is intended to provide an up-to-date overview of the strategies available to detect malingered symptoms following whiplash. Whiplash-associated disorders (WADs) represent the most common traffic injuries, having a major impact on economic and healthcare systems worldwide. Heterogeneous symptoms that may arise following whiplash injuries are difficult to objectify and are normally determined based on self-reported complaints. These elements, together with the litigation context, make fraudulent claims particularly likely. Crucially, at present, there is no clear evidence of the instruments available to detect malingered WADs. Methods We conducted a targeted literature review of the methodologies adopted to detect malingered WADs. Relevant studies were identified via Medline (PubMed) and Scopus databases published up to September 2020. Results Twenty-two methodologies are included in the review, grouped into biomechanical techniques, clinical tools applied to forensic settings, and cognitive-based lie detection techniques. Strengths and weaknesses of each methodology are presented, and future directions are discussed. Conclusions Despite the variety of techniques that have been developed to identify malingering in forensic contexts, the present work highlights the current lack of rigorous methodologies for the assessment of WADs that take into account both the heterogeneous nature of the syndrome and the possibility of malingering. We conclude that it is pivotal to promote awareness about the presence of malingering in whiplash cases and highlight the need for novel, high-quality research in this field, with the potential to contribute to the development of standardised procedures for the evaluation of WADs and the detection of malingering.Open access funding provided by Universita degli Studi di Padova within the CRUI-CARE Agreement. This work was supported by funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 777090.Monaro, M.; Baydal Bertomeu, JM.; Zecchinato, F.; Fietta, V.; Sartori, G.; De Rosario Martínez, H. (2021). The detection of malingering in whiplash-related injuries: a targeted literature review of the available strategies. International Journal of Legal Medicine. 135(5):2017-2032. https://doi.org/10.1007/s00414-021-02589-wS20172032135

Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion

[EN] We propose to model planar movements between two human segments by means of rolling-without-slipping kinematic pairs. We compute the path traced by the instantaneous center of rotation (ICR) as seen from the proximal and distal segments, thus obtaining the fixed and moving centrodes, respectively. The joint motion is then represented by the rolling-without-slipping of one centrode on the other. The resulting joint kinematic model is based on the real movement and accounts for nonfixed axes of rotation; therefore it could improve current models based on revolute pairs in those cases where joint movement implies displacement of the ICR. Previous authors have used the ICR to characterize human joint motion, but they only considered the fixed centrode. Such an approach is not adequate for reproducing motion because the fixed centrode by itself does not convey information about body position. The combination of the fixed and moving centrodes gathers the kinematic information needed to reproduce the position and velocities of moving bodies. To illustrate our method, we applied it to the flexion-extension movement of the head relative to the thorax. The model provides a good estimation of motion both for position variables (mean R pos=0.995) and for velocities (mean R vel=0.958). This approach is more realistic than other models of neck motion based on revolute pairs, such as the dual-pivot model. The geometry of the centrodes can provide some information about the nature of the movement. For instance, the ascending and descending curves of the fixed centrode suggest a sequential movement of the cervical vertebrae. © 2010 Elsevier Ltd.This work was funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2006-14722-C02-01, DPI2006-14722-C02-02, DPI2009-13830-C02-01, DPI2009-13830-C02-02 and Ramon y Cajal contract to JAG).Page Del Pozo, AF.; De Rosario Martínez, H.; Galvez Griso, JA.; Mata Amela, V. (2011). Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion. Journal of Biomechanics. 44(4):747-750. https://doi.org/10.1016/j.jbiomech.2010.11.019S74775044

Model of Soft Tissue Artifact Propagation to Joint Angles in Human Movement Analysis

[EN] This work describes the kinematic laws that govern the transmission of soft tissue artifact errors to kinematic variables in the analysis of human movements. Artifacts are described as relative translations and rotations of the marker cluster over the bone, and a set of explicit expressions is defined to account for the effect of that relative motion on different representations of rotations: the rotation around the screw axis, or rotation vector, and three Euler angle sequences (XY0Z, YX0Y00, ZX0 Y00). Although the error transmission is nonlinear in all cases, the effect of artifacts is greater on Euler sequences than on the rotation vector. Specifically, there are crosstalk effects in Euler sequences that amplify the errors near singular configurations. This fact is an additional source of variability in studies that describe artifacts by comparing the Euler angles obtained from skin markers, with the angles of an artifact-free gold standard. The transmission of errors to rotation vector coordinates is less variable or dependent on the type of motion. This model has been tested in an experiment with a deformable mechanical model with a spherical joint.This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01 and DPI2009-13830-C02-02).Page Del Pozo, AF.; De Rosario Martínez, H.; Mata Amela, V.; Besa Gonzálvez, AJ. (2014). Model of Soft Tissue Artifact Propagation to Joint Angles in Human Movement Analysis. Journal of Biomechanical Engineering. 136:1-7. doi:10.1115/1.4026226S1713

Propagation of Artifact Errors on Kinematic Variables. Effect on Euler Angles

This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01, DPI2009-13830- C02-02 and IMPIVA IMIDIC/2010/84)De Rosario Martínez, H.; Page Del Pozo, AF.; Mata Amela, V.; Besa Gonzálvez, AJ.; Moreno Cano, R. (2012). PROPAGATION OF ARTIFACT ERRORS ON KINEMATIC VARIABLES. EFFECT ON EULER ANGLES. Journal of Biomechanics. 45:293-293. doi:10.1016/S0021-9290(12)70294-4S2932934

Kinematic description of soft tissue artifacts: quantifying rigid versus deformation components and their relation with bone motion

[EN] This paper proposes a kinematic approach for describing soft tissue artifacts (STA) in human movement analysis. Artifacts are represented as the field of relative displacements of markers with respect to the bone. This field has two components: deformation component (symmetric field) and rigid motion (skew-symmetric field). Only the skew-symmetric component propagates as an error to the joint variables, whereas the deformation component is filtered in the kinematic analysis process. Finally, a simple technique is proposed for analyzing the sources of variability to determine which part of the artifact may be modeled as an effect of the motion, and which part is due to other sources. This method has been applied to the analysis of the shank movement induced by vertical vibration in 10 subjects. The results show that the cluster deformation is very small with respect to the rigid component. Moreover, both components show a strong relationship with the movement of the tibia. These results suggest that artifacts can be modeled effectively as a systematic relative rigid movement of the marker cluster with respect to the underlying bone. This may be useful for assessing the potential effectiveness of the usual strategies for compensating for STA. © 2012 International Federation for Medical and Biological Engineering.This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01, DPI2009-13830-C02-02 and IMPIVA IMDEEA/2012/79 and IMDEEA/2012/80).De Rosario Martínez, H.; Page Del Pozo, AF.; Besa Gonzálvez, AJ.; Mata Amela, V.; Conejero Navarro, E. (2012). Kinematic description of soft tissue artifacts: quantifying rigid versus deformation components and their relation with bone motion. Medical & Biological Engineering & Computing. 50(11):1173-1181. https://doi.org/10.1007/s11517-012-0978-5S117311815011Akbarshahi M, Schache AG, Fernandez JW, Baker R, Banks S, Pandy MG (2010) Non-invasive assessment of soft-tissue artifact and its effect on knee joint kinematics during functional activity. J Biomech 43:1292–1301Alexander EJ, Andriacchi TP (2001) Correcting for deformation in skin-based marker systems. J Biomech 34:355–361Andersen MS, Benoit DL, Damsgaard M, Ramsey DK, Rasmussen J (2010) Do kinematic models reduce the effects of soft tissue artefacts in skin marker-based motion analysis? An in vivo study of knee kinematics. J Biomech 43:268–273Andriacchi TP, Alexander EJ, Toney MK, Dyrby C, Sum J (1998) A point cluster method for in vivo motion analysis: applied to a study of knee kinematics. J Biomech Eng 120:743–749Benoit DL, Ramsey DK, Lamontagne M, Xu L, Wretenberg P, Renström P (2006) Effect of skin movement artifact on knee kinematics during gait and cutting motions measured in vivo. Gait Posture 24:152–164Camomilla V, Donati M, Stagni R, Cappozzo A (2009) Non-invasive assessment of superficial soft tissue local displacement during movement: a feasibility study. J Biomech 42:931–937Cappello A, Cappozzo A, La Palombara PF, Lucchetti L, Leardini A (1997) Multiple anatomical landmark calibration for optimal bone pose estimation. Hum Mov Sci 16:259–274Cappello A, Stagni R, Fantozzi S, Leardini A (2005) Soft tissue artifact compensation in knee kinematics by double anatomical landmark calibration: performance of a novel method during select motor tasks. IEEE Trans Biomed Eng 52:992–998Cappozzo A, Della Croce U, Leardini A, Chiari L (2005) Human movement analysis using stereophotogrammetry: part 1: theoretical background. Gait Posture 21:186–196Chèze L, Fregly BJ, Dimnet J (1995) A solidification procedure to facilitate kinematic analyses based on video system data. J Biomech 28:879–884Dumas R, Cheze L (2009) Soft tissue artifact compensation by linear 3D interpolation and approximation methods. J Biomech 42:2214–2217Ehrig RM, Taylor WR, Duda GN, Heller MO (2006) A survey of formal methods for determining the centre of rotation of ball joints. J Biomech 39:2798–2809Ehrig RM, Taylor WR, Duda GN, Heller MO (2007) A survey of formal methods for determining functional joint axes. J Biomech 40:2150–2157Fuller J, Liu LJ, Murphy MC, Mann RW (1997) A comparison of lower-extremity skeletal kinematics measured using skin- and pin-mounted markers. Hum Mov Sci 16:219–242Gao B, Zheng N (2008) Investigation of soft tissue movement during level walking: translations and rotations of skin markers. J Biomech 41:3189–3195Holden JP, Orsini JA, Siegel KL, Kepple TM, Gerber LH, Stanhope SJ (1997) Surface movement errors in shank kinematics and knee kinetics during gait. Gait Posture 5:217–227Leardini A, Chiari L, Della Croce U, Cappozzo A (2005) Human movement analysis using stereo photogrammetry: part 3. Soft tissue artifact assessment and compensation. Gait Posture 21:212–225Lucchetti L, Cappozzo A, Cappello A, Della Croce U (1998) Skin movement artefact assessment and compensation in the estimation of knee-joint kinematics. J Biomech 31:977–984Nester C, Jones RK, Liu A, Howard D, Lundberg A, Arndt A, Lundgren P, Stacoff A, Wolf P (2007) Foot kinematics during walking measured using bone and surface mounted markers. J Biomech 40:3412–3423Page A, de Rosario H, Mata V, Hoyos JV, Porcar R (2006) Effect of marker cluster design on the accuracy of human movement analysis using stereophotogrammetry. Med Biol Eng Comput 4:1113–1119Page A, de Rosario H, Mata V, Atienza C (2009) Experimental Analysis of Rigid Body Motion. A Vector Method to Determine Finite and Infinitesimal Displacements From Point Coordinates. J Mech Des 131: 031005Page A, Galvez JA, de Rosario H, Mata V, Prat J (2010) Optimal average path of the instantaneous helical axis in planar motions with one functional degree of freedom. J Biomech 43:375–378Peters A, Galna B, Sangeux M, Morris M, Baker R (2010) Quantification of soft tissue artifact in lower limb human motion analysis: a systematic review. Gait Posture 31:1–8Reinschmidt C, van den Bogert AJ, Lundberg A, Nigg BM, Murphy N, Stacoff A, Stano A (1997) Tibiofemoral and tibiocalcaneal motion during walking: external vs. skeletal markers. Gait Posture 6:98–109Ryu T, Choi HS, Chung MK (2009) Soft tissue artifact compensation using displacement dependency between anatomical landmarks and skin markers- a preliminary study. Int J Ind Ergon 39:152–158Sangeux M, Marin F, Charleux F, Dürselen L, Ho Ba Tho MC (2006) Quantification of the 3D relative movement of external marker sets vs. bones based on magnetic resonance imaging. Clin Biomech 21:984–991Sati M, de Guise JA, Larouche S, Drouin G (1996) Quantitative assessment of skin-bone movement at the knee. Knee 3(3):121–138Stagni R, Fantozzi S (2009) Can cluster deformation be an indicator of soft tissue artefact? Gait Posture 30(Suppl 1):S55Stagni R, Fantozzi S, Cappello A, Leardini A (2005) Quantification of soft tissue artefact in motion analysis by combining 3D fluoroscopy and stereophotogrammetry: a study on two subjects. Clin Biomech 20(3):320–329Stagni R, Fantozzi S, Cappello A (2009) Double calibration vs global optimization: performance and effectiveness for clinical application. Gait Posture 29:119–122Taylor WR, Ehrig RM, Duda GN, Schell H, Seebeck P, Heller MO (2005) On the influence of soft tissue coverage in the determination of bone kinematics using skin markers. J Orthop Res 23(4):726–734Tranberg R, Karlsson D (1998) The relative skin movement of the foot: a 2-D roentgen photogrammetry study. Clin Biomech 13(1):71–76Tsai T-Y, Lu Tung-Wu, Kuo M-Y, Lin C–C (2011) Effects of soft tissue artifacts on the calculated kinematics and kinetics of the knee during stair-ascent. J Biomech 44(6):1182–1188Woltring HJ, Long K, Osterbauer PJ, Fuhr AW (1994) Instantaneous helical axis estimation from 3-D video data in neck kinematics for whiplash diagnostics. J Biomech 27(12):1415–143