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1.
Matteo Zago Andrea Gianluca Piovan Isabella Annoni Daniela Ciprandi F. Marcello Iaia 《Journal of sports sciences》2016,34(5):411-419
Dribbling speed in soccer is considered critical to the outcome of the game and can assist in the talent identification process. However, little is known about the biomechanics of this skill. By means of a motion capture system, we aimed to quantitatively investigate the determinants of effective dribbling skill in a group of 10 Under-13 sub-elite players, divided by the median-split technique according to their dribbling test time (faster and slower groups). Foot-ball contacts cadence, centre of mass (CoM), ranges of motion (RoM), velocity and acceleration, as well as stride length, cadence and variability were computed. Hip and knee joint RoMs were also considered. Faster players, as compared to slower players, showed a 30% higher foot-ball cadence (3.0 ± 0.1 vs. 2.3 ± 0.2 contacts · s?1, P < 0.01); reduced CoM mediolateral (0.91 ± 0.05 vs. 1.14 ± 0.16 m, P < 0.05) and vertical (0.19 ± 0.01 vs. 0.25 ± 0.03 m, P < 0.05) RoMs; higher right stride cadence (+20%, P < 0.05) with lower variability (P < 0.05); reduced hip and knee flexion RoMs (P < 0.05). In conclusion, faster players are able to run with the ball through a shorter path in a more economical way. To effectively develop dribbling skill, coaches are encouraged to design specific practices where high stride frequency and narrow run trajectories are required. 相似文献
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An application of the Udwadia-Kalaba dynamic formulation to flexible multibody systems 总被引：1，自引：0，他引：1
For the transient response analysis of a flexible slider-crank mechanism, the coordinate partitioning scheme and the Udwadia-Kalaba formulation are herein compared. The flexibility of the coupler has been modelled by means of a single Timoshenko beam element. The present analytical treatment can be viewed as an extension of the model discussed by Shabana in his textbook. 相似文献
3.
Talis Tisenkopfs Ilona Kunda Sandra šūmane Gianluca Brunori Laurens Klerkx Heidrun Moschitz 《The Journal of Agricultural Education and Extension》2015,21(1):13-33
AbstractPurpose: The paper explores the role of boundary work and boundary objects in enhancing learning and innovation processes in hybrid multi-actor networks for sustainable agriculture (LINSA).Design/Methodology/Approach: Boundary work in LINSA is analysed on the basis of six case studies carried out in SOLINSA project under a common methodology. In developing typologies of boundary work and objects, a grounded approach is used.Findings: LINSA analysis demonstrates the dynamic character, diverse forms and multiple functions of boundary work and objects in three domains: learning, innovation, and sustainability. Addressing specific types of goals and actors leads to specific types of boundary work and boundary objects. Context-appropriate boundary work allows aligning differing actor attitudes, gaining increased external support, and developing LINSA. The concepts of boundary work and boundary objects are relevant in a broad range of divergent LINSA settings. Boundary work has its limitations, but its facilitation supports reaching LINSA goals.Practical Implications: The paper proposes recognising context-appropriate forms of boundary work and skilful use of emerging boundary objects to both promote internal consolidation of LINSA and effective external communication to foster learning and innovation for sustainability.Originality/Value: The paper provides insights into the forms, dynamic and outcomes of boundary work in LINSA in three key domains: developing shared knowledge base, co-producing innovation and negotiating sustainability. 相似文献
4.
Björn Sjögren Robert Thornberg Linda Wänström Gianluca Gini 《Psychology in the schools》2020,57(11):1710-1723
This study examined whether defending and passive bystanding during peer victimization episodes were associated with individual- and classroom-level efficacy to stop peer victimization. Self-report survey data were analyzed from 1,467 Swedish fourth-grade students (mean age = 10.55) from 100 classrooms in 63 schools. Multilevel analyses revealed that, when witnessing peer victimization, students more often defended victims if they were high in defender self-efficacy and if they belonged to classrooms high in collective efficacy. In contrast, students were more likely to remain passive if they were low in defender self-efficacy and if they belonged to classrooms low in collective efficacy. Taken together, our findings suggest that efficacy beliefs both at the individual and at the classroom level contribute to explaining variability in students' bystander behaviors, which has potential implications for prevention and intervention work. 相似文献
5.
SYNOPSISHigh-quality parental caregiving promotes children’s development from their day of birth or even earlier. Whether there are ways to predict, and ultimately enhance, parental caregiving quality during the prenatal stages of development has been less well understood. This circumstance is even truer when things do not go according “to plan.” In this commentary, we explore two possible scenarios, perhaps unexpected for expectant parents, that can affect children’s development: (1) postpartum parental displays of atypical behaviors and parental caregiving strategies (i.e., maternal/paternal depression) and (2) postpartum child displays of atypical behaviors (i.e., autism spectrum disorder). 相似文献
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Gianluca Demartini Claudiu S. Firan Tereza Iofciu Ralf Krestel Wolfgang Nejdl 《Information Retrieval》2010,13(5):534-567
Entity Retrieval (ER)—in comparison to classical search—aims at finding individual entities instead of relevant documents.
Finding a list of entities requires therefore techniques different to classical search engines. In this paper, we present
a model to describe entities more formally and how an ER system can be build on top of it. We compare different approaches
designed for finding entities in Wikipedia and report on results using standard test collections. An analysis of entity-centric
queries reveals different aspects and problems related to ER and shows limitations of current systems performing ER with Wikipedia.
It also indicates which approaches are suitable for which kinds of queries. 相似文献
8.
Nadia Cristina Valentini Licia Pierosan Mary E. Rudisill Peter A. Hastie 《Physical Education & Sport Pedagogy》2017,22(4):349-363
Background: Fundamental motor skill proficiency is essential for engagement in sports and physical play and in the development of a healthy lifestyle. Children with motor delays (with and without disabilities) lack the motor skills necessary to participate in games and physical activity, and tend to spend more time as onlookers than do their peers. As such, intervention programs are crucial in promoting motor skill development of children with motor delays. While mastery climate (MC) interventions have shown to positively impact children’s motor performance, what is unknown is the impact of cognitive strategies used by children within these climates. Furthermore, although vigorous play seems to be related to the development of gross motor skills, it is still unknown if children with and without disabilities would benefit from exercise play (EP) interventions.Purpose: This study examined the effects of MC and EP interventions on the motor skill development and verbal recall (VR) of children with motor delays. The sample included children with and without disabilities.Research designs: One hundred and thirty-eight children from 27 urban public schools were referred to the present study. Children were assessed using the Test of Gross Motor Development second edition (TGMD-2) and a VR checklist. Sixty-four children (18 with disabilities and 46 without) met the inclusion criteria, which was a score less than the fifth percentile on the TGMD-2. Participants were randomly assigned to the MC or EP 14-week interventions emphasizing gross motor skill practice.Data collection and analysis: Children were assessed at pre- and post-intervention. A 2 (groups)?×?2 (disability) × 2 (time) analyses of variance with repeated measures on the last factor was conducted. Change scores, t-test comparisons on the delta scores and Cohen’s D were also calculated.Results: The MC group demonstrated significant and positive changes over the intervention period. Further, the MC group showed superior locomotor and object control performance and higher recall of verbal cues (p?≤?.05) at post-intervention compared to the EP group. Children with and without disabilities within the MC showed similar patterns of improvement. The EP intervention did not demonstrate significant improvements.Conclusion: Children with and without disabilities showed improvements in motor skills and VR when exposed to an MC, incorporating the six TARGET structures. These structures included (a) providing feedback and encouragement, providing opportunities for decision-making and establishing personal goals, (b) including parents in the recognition of children’s achievements, (c) creating opportunities to experience leadership and self-pacing, (d) guiding children to use verbal cues and modeling when practicing gross motor skills, and (e) providing demonstrations and teaching children to self-monitor their performance. Instruction is therefore seen as critical to learning gross motor skills, as demonstrated from the findings. Although there were opportunities for vigorous play within the EP intervention, the children did not show improvements in motor performance or VR. These findings suggest that new trends in teacher education physical education to prioritize physical activity over good motor skill instruction may not be advantageous for children in the early years, and should be reconsidered. 相似文献
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Gianluca Vernillo Aldo Savoldelli Andrea Zignoli Spyros Skafidas Alessandro Fornasiero Antonio La Torre 《Journal of sports sciences》2015,33(19):1998-2005
This study aimed to determine whether the fatigue induced by a mountain ultramarathon (MUM) led to changes in energy cost and kinematic during level and graded running. Pre- and post-race, 14 ultratrail runners ran on a level, uphill (5%) and downhill (5%) treadmill at 10 km · h?1. Kinematic data were acquired using a photocell system. Post-race, the downhill energy cost increased by 13.1% (P < 0.001). No change was noted in level and uphill running. Duty factor and stride frequency were increased, whereas swing time, cycle time and stride length were decreased in all conditions (P < 0.05). Contact time was increased and the rate of force generation was decreased only in the uphill and downhill conditions (P < 0.05). Positive correlations were observed between performance time and the pre- to post-changes in the energy cost of level (r = 0.52, P = 0.04) and uphill running (r = 0.50, P = 0.04). MUM-induced fatigue resulted in physiological and spatiotemporal changes, though the response to fatigue varied considerably between running conditions. These changes resulted in a significant increment only in the downhill energy cost. Incorporating downhill locomotion in the training programmes of ultratrailers may help to improve performance-related physiological and biomechanical parameters. 相似文献
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Dynamic squat is one of the most executed fitness exercise. Its use is widespread both for rehabilitation and training purposes. Several typologies of the squat exercise can be performed. The most important are the front squat and the back squat. In the front squat the barbell is held in front of the body across the clavicles and deltoids, while in the back squat exercise the bar is held on the back of the body at the base of the neck. In this paper we will refer to dynamic back squat. The squat exercise can be performed with or without the help of a machine that has the scope of guiding the person during the movement and ensuring his stability and safety. The use of this type of machine is often necessary when the workout is heavy and the risk of incorrect exercise and injuries is high. On the other hand, the rigid structure of this device often overconstrains the lifting movement. From all these observations, the purpose of the paper is to discuss an alternative design of a mechanism able to maintain the advantage to allow a free-body execution and to preserve the safety of the athletes as well. The proposed mechanism has been designed starting from an anthropometric study on the squat movement. This has been performed by using a motion capture system and applying computer-aided engineering techniques. The design activity started from the experimental investigation of the trajectory of the barbell during the natural execution of the unrestricted back squat exercise. The tests have been performed on several subjects with different mass, anthropometry and gender. In a second phase, the data have been processed and analyzed and a specific mechanism, able to reproduce the natural trajectories, has been synthetized. Finally, the design and optimization of the entire structure has been performed through the use of virtual prototyping techniques. 相似文献