Effect of postural changes on 3D joint angular velocity during starting block phase     

Jean Slawinski  Raphaël Dumas  Laurence Cheze  Guy Ontanon  Christian Miller  Alice Mazure–Bonnefoy 《Journal of sports sciences》2013,31(3):256-263

Abstract

Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis® system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.  相似文献   

Execution time,kinetics, and kinematics of the mae-geri kick: Comparison of national and international standard karate athletes     

Joël Pozo  Guillaume Bastien 《Journal of sports sciences》2013,31(14):1553-1561

Abstract

Little is known of the performance characteristics of the shotokan karate mae-geri kick. The aim of this study was to compare the execution time, the lower limb kinetics and kinematics, and their respective repeatability in the mae-geri kick of karate athletes of two different standards. Seventeen adult black belt karate competitors (9 national and 8 international athletes) performed six kicks with their dominant lower limb on a striking surface, combining maximum force impact and velocity. Execution time of movement and lower limb kinematics were recorded with a high-speed camera. Maximum force at impact and the forces exerted on the ground were measured using three force plates. The duration of the kick was significantly shorter for international than for national standard athletes. However, no significant difference in the maximum impact force of the kick was observed between the two groups. In addition, significant kinematic differences were observed between the groups, with two angles of motion and one velocity peak occurring sooner in the kick movement for the international athletes, specifically for the knee joint. International athletes also performed the kick with a significantly higher repeatability for duration and kinematics, specifically during the pre-loading phase that precedes the attack phase. We conclude that theduration of the kick and repeatability of lower limb kinematics could be useful in selecting top-level karate athletes and monitoring their training status.  相似文献   

Numerical estimation in adults with and without developmental dyscalculia     

Sandrine Mejias  Jacques Grégoire  Marie-Pascale Noël 《Learning and individual differences》2012,22(1):164-170

It has been hypothesized that developmental dyscalculia (DD) is either due to a defect of the approximate number system (ANS) or to an impaired access between that system and symbolic numbers. Several studies have tested these two hypotheses in children with DD but none has dealt with adults who had experienced DD as children.This study aimed to compare these two hypotheses in an adult population in order to investigate which deficits still persist at that age. To that aim, numerical estimation tasks were given to adults who had or had not experienced DD as a child. Three of the estimation tasks required a mapping between the ANS and symbolic numbers: participants had to estimate the number of same or different-sized dots presented by producing the corresponding Arabic number or, conversely, to produce the number of dots corresponding to a presented Arabic number. A fourth task did not require any processing of symbolic numbers; participants had to produce a collection of dots of the same numerosity as another one previously presented.Consistently, in all the four numerical tasks and irrespective of whether the tasks used symbolic numbers or not, the estimates of DD participants were less accurate than those of the control participants. These results indicate that adults who had experienced DD as children continue to demonstrate a less precise magnitude representation.  相似文献   

Dynamic task selection: Effects of feedback and learner control on efficiency and motivation     

Gemma Corbalan  Liesbeth Kester  Jeroen J.G. van Merriënboer 《Learning and Instruction》2009,19(6):455-465

Structural features of learning tasks are relevant for problem solving but not salient for novice learners. Feedback in the form of Knowledge of Correct Response (KCR) during practice is expected to help learners recognize the structural features and to profit from learner control over the selection of learning tasks. A 2 × 2 factorial experiment (N = 118) was conducted to study the effects of the KCR feedback (present and absent) and control over the selection of learning tasks (learner control and program control). The presence of the KCR feedback yielded higher efficiency on a near-transfer test as well as higher learner motivation. An interaction between feedback and control, indicating extra beneficial effects of feedback when learners control the selection of learning tasks, was not found. Theoretical and practical implications are discussed.  相似文献   

The relationship between teaching practices and student achievement in first year classes     

Joël Clanet 《European Journal of Psychology of Education - EJPE》2010,25(2):192-206

This study investigated the links between the teaching practices of primary school teachers (n = 200) who were observed while presenting a new text to their first year classes, and the student achievement levels in those classes. The teaching practices are specifically concerned with the way the teachers supported and encouraged students’ activities during verbal interactions. Two different populations were observed: classes of first year students with a reduced teacher–student ratio (about ten students per class) and classes with a normal teacher–student ratio (between 20 and 25 students per class). We found that the average level of student achievement in the reduced size classes was higher than in the standard size classes but that teaching practices differed only at precise periods of group or individual introduction to new reading texts. In these periods, we found links between teaching practices and student achievement.  相似文献   

Reading during sentence composing and error correction: A multilevel analysis of the influences of task complexity     

Luuk Van Waes  Mari?lle Leijten  Thomas Quinlan 《Reading and writing》2010,23(7):803-834

In this study we investigated the role of reading, how writers coordinate editing with other writing processes. In particular, the experiment examines how the cognitive demands of sentence composing and the type of error influence the reading and writing performance. We devised an experimental writing task in which participants corrected an embedded error (orthographic near-neighbors or far-neighbors) and completed a sentence (using 1 or 3 context words)—in either order. Data were collected by logging keystrokes and recording eye-movements. The results revealed that both error and sentence complexity influenced the approach to error-correcting. Participants generally completed the partial sentence first, and then corrected the error (approximately 90% of the items). Task complexity reinforced this tendency. Moreover, in most of these cases, the error was fixated at least once prior to sentence completion. This suggests that the error was detected (at least partially), but the correction response was inhibited. The differences in cognitive load also affect the reading activity during planning. This investigation illustrates how the interplay of two task factors, error and sentence complexity, appears to influence how writers coordinate error-correcting with sentence composing.  相似文献   

The Impact of an Engineering Design Curriculum on Science Reasoning in an Urban Setting   总被引：2，自引：2，他引：0  

Eli M. Silk  Christian D. Schunn  Mari Strand Cary 《Journal of Science Education and Technology》2009,18(3):209-223

This study examines the use of engineering design to facilitate science reasoning in high-needs, urban classrooms. The Design for Science unit utilizes scaffolds consistent with reform science instruction to assist students in constructing a design solution to satisfy a need from their everyday lives. This provides a meaningful context in which students could reason scientifically. Eighth grade students from two urban schools participated in the unit. Both schools contained large percentages of racial/ethnic minority and economically disadvantaged students. Students demonstrated statistically significant improvement on a paper-and-pencil, multiple-choice pre and post assessment. The results compare favorably with both a high-quality inquiry science unit and a traditional textbook curriculum. Implications for the use of design-based curricula as a viable alternative for teaching science reasoning in high-needs, urban settings are discussed.

Eli M. SilkEmail:

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Value orientations of elementary and secondary physical education teachers in Flanders     

Behets D  Vergauwen L 《Research quarterly for exercise and sport》2004,75(2):156-164

The purpose of this research was to examine and compare physical educators'value profiles. The Value Orientation Inventory was used to collect data from 528 elementary and 637 secondary physical education teachers in Flanders. Teacher characteristics, including gender and years of teaching experience revealed only minor differences in value orientations. Significant differences in teachers' value orientations were observed between teachers in elementary and secondary schools. The different value profiles of these two teacher groups are discussed in the perspective of the recently introduced conceptual innovations in physical education mandated by the Flemish government. The teachers at the elementary level placed a high priority on the disciplinary mastery and the self-actualization orientations; those at the secondary level scored high on the social responsibility and disciplinary mastery orientations. The findings from this study suggest that teaching level influences teachers' value orientation. Teachers appeared to adjust their curricular priorities to meet the demands and needs of students in elementary versus secondary schools.  相似文献   

Reported childhood sexual abuse and eating-disordered cognitions and behaviors     

van Gerko K  Hughes ML  Hamill M  Waller G 《Child abuse & neglect》2005,29(4):375-382

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The Iowa distance education alliance   总被引：1，自引：0，他引：1  

Michael Simonson  Jan Sweeney  Mari Kemis 《TechTrends》1993,38(1):25-28

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