Evaluación de parámetros biomecánicos del lanzamiento de jabalina en lanzadores de diferente nivel de rendimiento

Mediante análisis cinemático y utilizando como muestra a lanzadores agrupados en función de la marca conseguida (grupo internacional: atletas con marca superior a los 80 metros; y grupo nacional: atletas con marca inferior a 80 metros) el objetivo del estudio se centró en determinar si alguno de los parámetros utilizados para evaluar la eficacia del gesto establece diferencias entre uno y otro grupo de lanzadores. Los resultados muestran que algunos de dichos parámetros cinemáticos ayudan a establecer los márgenes para la pertenencia a los. Del total de las 41 variables contrastadas, sólo 8 de ellas establecían diferencias significativas entre grupos para un nivel de confianza del 95%: velocidad de lanzamiento; velocidad máxima alcanzada por el codo; velocidad del codo en el instante del despegue; la altura de lanzamiento; la inclinación lateral de la línea de los hombros al inicio de la fase final; el ángulo de rotación de las caderas y de los hombros en el plano horizontal en el inicio de la fase final; y el ángulo de posición de la jabalina en el instante del despegue. El estudio se realizó a partir de los resultados obtenidos en el desarrollo del proyecto financiado por la Comisión Interministerial de Ciencia y Tecnología - CICYT (SAF95-0721-C04-04), y el proyecto financiado por el Ministerio de Educación, Cultura y Deporte junto al Centro de Investigación en Ciencias del Deporte, de referencia 08/UNI22/97, y la colaboración de la Unidad de Biomecánica del CARICD de Madrid.Peer Reviewe

ANALYSIS OF TETHERED SWIMMING FORCE, TETHERED SWIMMING POWER, SWIMMING SPEED AND ANTROPOMETRICAL CHARACTERISTICS OF YOUNG SWIMMERS IN CRAWL STROKE

Propulsive forces, instantaneous power and swimming velocity in semi-tethered swimming were measured in a group of 69 competitive swimmers. Also, isometric force in laboratory, best 15 m swimming velocity and 100 m freestyle personal mark and anthropometric characteristics were recorded. The results show the high relationship between swimming speed and the propulsive forces, and the instantaneous power. Consequently, the above mentioned variables can be useful for the evaluation of the swimmers along a season

Microstructural evolution of a modified HP alloy: experimental and complementary computational study

In this work is presented results of the microstructural characterization of austenitic stainless steel (HP series) modified with Nb, aged at temperatures of 750, 800, 850, 900 and 950oC in air at different times. Microstructural changes were analyzed using optical microscopy, scanning electron microscopy (SEM) equipped with (EDS), x-ray diffraction and Vickers hardness. In the as-cast condition, the microstructure consists of an austenitic matrix and eutectic carbides network, Cr, Nb-rich carbides. The Cr-rich carbides are M7C3 type, whereas, those rich in Nb are NbC. During aging, there is a second precipitation in the matrix of very fine needle form of M23C6 carbides, which leads to an increase in hardness. After that, the decreasing in hardness is associated with a coalescence phenomenon of the secondary precipitates. Computational modeling shows that M23C6 is lesser stable than M7C3 carbide

An Eulerian-Lagrangian Coupled Model for Droplets Dispersion from Nozzle Spray

In this chapter, an Euler-Lagrangian double-way coupled model is presented for simulating the liquid particle dispersion ejected from a high-pressure nozzle. The Eulerian code is advanced regional prediction system (ARPS), developed by Center of Analysis and Prediction of Storm (CAPS) and Oklahoma University, USA, which is specialized in weather simulation. This code is the double way coupled with a Lagrangian one-particle model. The theoretical remarks of the double-way coupling, the simulation of the liquid droplet trajectory, and, finally, the droplet collision in the spray cloud using a binary collision model are descripts. The results of droplet velocities and diameters are compared with experimental laboratory measurements. Finally, agrochemical spraying over a cultivated field in weak wind and high air temperature conditions is showed

INFLUENCE OF FOOTWEAR ON THE ANKL SPRAIN PRODUCTION MECHANISM IN BASKETBALL

INTRODUCTION: Vertical jump is a usual movement pattern in basketball, and it is related to ankle injuries, mainly during rebound actions when falling on another player's foot. The aim of the present study IS to determine the influence of the introduction of certain elements in the footwear on ankle protection when falling on an irregular surface. The study consisted in simulating a rebound action in which the player jumps and falls on an irregular surface, simulated by a 20" inclined plane. 12 footwear prototypes were studied, making a factorial design with the following elements: high or low top, upper vamp stabilizer, hollow midsole at midfoot level and lace anchors. 3 test subjects, students of Physical Education, took part. They performed 36 jumps each, in series of 3, with a recovering time of 3 s between jumps and 3 m between series. Each series was done wearing one of the 12 prototypes at random. Each jump was filmed at 150 Hz and then digitized. The angles of knee and ankle were calculated as a function of time. For the statistical analysis an analysis of variance (ANOVA) was made, considering as factors the elements introduced in the footwear and a level of significance of 0,05 was chosen. RESULTS: The results indicate the high top footwear limited the range of movement during ankle flexion-extension and they produce higher values of inversion than low top. With an upper vamp stabilizer, higher values of inversion were obtained than without it. On the other hand, with a hollow midsole, inversion values were lower. Introducing a movement control system in the rearfoot, by means of lace anchors, did not show influence on the studied movements. CONCLUSIONS: In this way, after landing on an irregular surface, the high top as well as an upper vamp stabilizer increase the degree of inversion, probably because these elements rigidify vertically the footwear and increase the adherence to the floor or to the irregular surface on which the subject IS. However, it must be considered that epidemiological studies state that high top footwear diminish the risk of acute ankle injuries in basketball players. The upper vamp stabilizer, on the contrary, only rigidifies vertically the footwear and it dos not offer any extra reinforcement of the joint, increasing the risk of suffering ankle injuries. REFERENCES: Stacoff, A.; Kalin, X.; Stiitsi, E. (1 989) Torsional movements of the foot during landing. Abstracs of the XI1 Congress of the International Society of Biomechanics. Los Angeles, 1085. Sussman, D. H.; Hamill, J.; Miller, M. (1988) Effect of shoe height and prophylactic taping on ankle joint motion during s~mulated basketball rebounding. In De Groot, G., Hollander, A.P.; Huijing, P.A.; Van lngen Schenau, G.J. (Eds.) Biomechanics XI-6

INFLUENCE OF THE FOOTBALL BOOT DESIGN ON SHOCK ABSORPTION

INTRODUCTION: A number of studies about the importance of sports shoe design on injuries prevention have been published in late years (Masson, 1989;Stacoff, 1988). Epidemiological studies indicate that football has special relevance with relation to suffering injuries (Hoff,1986; Ydes, 1990). During the practice of football a number of movement patterns such as jumping or running are performed(Reilly, 1976), being shock absorption a basic criterion for the design of footwear in Worts where such movement patterns occur. To improve the shock absorption of footwear two strategies are often adopted: to potentiate the natural mechanisms by means Of a better the tissue heel Or to increase the shock absorption capability of the footwear appropriately selecting the materials of the sole and insole. The aim the study was to evaluate the effect which different boot designs and different sole and insole materials had on load transMission during running. Based on a preliminary study, 3 boot prototypes and 4 insole prototypes were made. 8healthy football players were selected and they performed 6 runs with each of the 12possible combinations of boot/insole. The runs were performed in a football field and a speed of 4 m/s was determined controlled by electric photocells. The sequence of each condition was randomized for each subject. The subjects were instrumented with 2 accelerometers, attached to their skin by means of a strong bandage on tibia and forehead. The signals from the accelerometers were connected to a telemetry equipment which allowed the subject freer movements. With parameters obtained, an analysis of variance (ANOVA) was made. The level of significance chosen was of alfa < 0.05. To analyze the differences between conditions, an LSD test was made. RESULTS: One of the viscoelastic materials inserted in the insole offered a mean reduction of impacts of about 6%.One of' the materials of the boot sole showed a better capability of shock absorption, about 7%. The boots to which a special compartment for the heel pad did not improve shock absorption. Acceleration measured at tibia was of 6.01+0.06 times gravity (g) and at head it was of 2.45+2g.CONCLUSION: According to the results, an appropriate selection of insole and boot materials an improvement of shock absorption of 13% can be obtained. Although the tests were made on a natural grass football field and the speed of run was not too high, the values found for both tibia and forehead were high: this fact confirms the hypothesis that shock absorption is a basic criterion in the design of football boots from the point of view of protection from injuries. REFERENCES: Hoff, G.L and Martin, T.A.(1986). Outdoor and Indoor soccer: Injuries among youth players. Am. J. Sp. Med. 8,231-233.Masson, M. and Hess, H. (1989) Typicalsoccer injuries. Their effects on the design of the athletic shoe. In 6. Segesser & W.Pforringer (Eds.) The shoe in sport.London: Wolfe Publishing, Lld., 89-95.Reilly, T. (1 976) A motion analysis of work rate in differential roles in professional football match play. J. Human Mov. Stud.2, 87-97.Stacoff, A,; Denoth, J.; Kaelin, X. and Stuessi, E. (1988) Running injuries and shoe construction: Some possible relantionships. lnt. J. Sports Biomech. 4,342-357.Yde, J. and Nielsen, A.B. (1990) Sport injuries in adolescents' ball games: soccer,handball and basketball. Br. J. Sp. Med24(1), 51-54.8

JOINT CO-ORDINATE SYSTEM AND ATTITUDE VECTOR: INFLUENCE IN THE INTERPRETATION OF MOVEMENTS

INTRODUCTION: A rapid lateral braking movement and a rapid turning movement were recorded with two cameras Photo Sonics 16mm at 200 frames/s. The different Joint Coordinate Systems and the attitude vector has a better behavior in these practical cases as suggested by H. Woltring and has the same anatomical sense that the most usual Joint Coordinate Systems. RESULTS: Four body segments were defined: foot, leg, thigh and hip. Three markers define the 3D position of each segment. The position of the markers was selected following the criteria that the movement of muscles and skin had not a big influence on the measurements. To define the anatomical axes the anthropometrical model proposed by Vaughan et al. (1992) was used with some variations, because of the supposition that some markers belong 'to two body segments at the same time is not correct in the movements studied. CONCLUSIONS: In the two movements studied the angle's curves calculated with the attitude vector have a form similar to those of the curves calculated with JCS-1 and JCS+1 which the Joint Coordinate Systems recommended as standard in Cole et al. (1993) and ISB (1995), but the absolute value of the angles is displaced. It is clear that the selection of the JCS has influence in the angle's value and, in some cases, it can change the description of the movement. The order of rotations in JCS are 123 (+1), 231 (+2), 312 (+3), 132 (-1), 321 (-2),213 (-3). In lateral braking movement JCS+3 changes the hip flexion for hip extension and knee flexion for knee extension. And 71 JCS-3 changes hip adduction for hip abduction and hip internal rotation for hip external rotation. In the turning movement JCS+2 changes hip flexion, hip adduction, knee adduction and ankle supination. JCS+3 changes hip flexion, hip adduction, knee extension and knee internal rotation. JCS-3 changes hip adduction. If only these JCS had been used, the description of movement would have been incongruent. Although the attitude vector has some mathematical advantages, the matter of wh ich is the more anatomical is still open. The attitude vector represents the movement in one helical displacement around an axis The different JCS represent the movement in three ordered helical displacements around three consecutive axes. REFERENCES: Cole, G.K.; Nigg, B.M.; Ronsky, J.L.; Yeadon, M.R. (1993) Application of the Joint Coordinate System to the Three Dimensional Joint Attitude and Movement Representation: A Standardization Proposal. Transactions of the ASME, 115,344-349. ISB (1995) A joint coordinate system for the ankle complex. ISB News'letter, 59, 6-8. Kapandji, IA (1988) Cuaderno 2: Miembro Inferior. Cuadernos de fisiologia articular.(Edited by Masson S.A.). Barcelona. Vaughan, C.L; Davis, B.L.; O'Connor, J.C. (1992) Dynamics of human gait. Human Kinetics Books, Champaign, IIlinois Woltring, H.J. (1994) 3-D attitude representation of human joints: a standardization proposal. J. Biomech. 27

Memoria Riojana

La Universidad Nacional de La Rioja busca generar un espacio de contención social donde sea posible que distintos actores puedan expresar sus sentimientos y relatar sus vivencias en relación a los últimos gobiernos de facto. Buscamos la construcción de la Identidad, recuperar la memoria histórica de la provincia y proyectar estos hechos en la promoción de los Derechos Civiles y Políticos. La propuesta es un Blog abierto destinado a la Construcción de la Identidad y la Memoria de nuestra provincia para realizar publicaciones sobre distintos temas relacionados a la memoria y derechos humanos. A través del recurso informático, tanto ex presos políticos, madres de desaparecidos, abogados, sacerdotes, docentes y público en general podrán aportar experiencia y memorias.  Asimismo se buscará resaltar la figura del monseñor Enrique Angelelli víctima del genocidio, generando un listado de centros de detención clandestinos en nuestra provincia. Con este blog, no pretendemos plantear la práctica militante desde su aspecto más negativo, más allá de este y de los silencios aún persistentes, pretendemos narraciones en términos de políticas actuales, de la identificación con los jóvenes, que actualmente eligen la militancia política como una iniciativa legítima para la transformación. Creemos que estos silencios pueden comenzar a circular por nuevos senderos. Especialmente respecto de cómo la persona que transita el presente se acerca al pasado y a su propia experiencia adoptando un punto de vista crítico o una mirada idealista. A nivel nacional, el Ministerio de Educación, cuenta con un Programa de Memoria y Derechos Humanos, que se aplica a docentes de nivel secundario. En esta instancia se busca lograr la participación de alumnos secundarios,  universitarios juntamente con instituciones civiles y constituirse en una fuente de información al respecto. La comunidad participará de este proyecto mediante una convocatoria específica que se realizará con la ONG (Mi Tierra) participante y el Ministerio de Educación a través de la Dirección General de Nivel Secundario, a fin de promocionar el Blog que se constituirá en fuente de promoción de artículos sobre Memoria y Derechos Humanos

Mathematics teachers’ ideas about mathematical models: a diverse landscape

This paper describes the ideas that mathematics teachers (grades 5-9) have regarding mathematical models of real-world phenomena, and explores how teachers’ ideas differ depending on their educational background. Participants were 56 United States in-service mathematics teachers. We analyzed teachers’ written responses to three open-ended questions through content analysis. A varied landscape of ideas was identified. Teachers referred to different entities as constituting models, expressed different ideas about whether data points can be part of models, and whether models convey more information than data. Interesting differences according to educational background were identified, especially between teachers with and without mathematics backgrounds