Differences in the utilisation of active power in squat and countermovement jumps     

Damián Ferraro  Gabriel Fábrica 《European Journal of Sport Science》2017,17(6):673-680

The aim of this article was to understand how active power is used in squat and countermovement jumps. A simple empirical model comprising a mass, a spring, an active element and a damper, together with an optimisation principle, was used to identify the mechanical factors that maximise performance of jumps without countermovement (squat jumps, SJ) and with countermovement (CMJ). Twelve amateur volleyball players performed SJ from two initial positions and CMJ with two degrees of counterbalancing, while kinematic data were collected (jump height, push-off duration and position of the centre of mass). The model adjusted well to real data of SJ through all the impulse phase, and slightly less adequately at the end of this phase for CMJ. Nevertheless, it provides a satisfactory explanation for the generation and utilisation of active power for both type of jumps. On average, the estimated power of the active elements, the spring, and the damper were greater in the SJ. Based upon the result obtained with this model, we suggest that active power is best evaluated with SJ. The reason for this is that, during this kind of jump, the elements associated with the damper consume much of the energy produced by the active elements. The participation of the elements that consume the energy generated by the active elements is less in CMJ than in SJ, allowing for a better utilisation of this energy. In this way it is possible to achieve a better performance in CMJ with less active power.  相似文献   

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners?     

J. Santos-Concejero  N. Tam  D. R. Coetzee  J. Oliván  T. D. Noakes  R. Tucker 《Journal of sports sciences》2017,35(6):531-538

The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h^?1 and 20 km ·h^?1). VO₂ and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg^?1· km^?1 at 12 km· h^?1 and 184.8 ± 9.9 ml· kg^?1· km^?1 at 20 km· h^?1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg^?1·km^?1 and 0.93 ± 0.07 kcal· kg^?1· km^?1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h^?1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.  相似文献   

Quality of Life of Children with Learning Disabilities: A Comparison of Self‐Reports and Proxy Reports          下载免费PDF全文

Halis Sakız  Zeynep Hande Sart  Bengü Börkan  Barış Korkmaz  Nalan Babür 《Learning disabilities research & practice》2015,30(3):114-126

This study aimed to explore how children with learning disabilities (LD) perceive their quality of life (QoL) and to compare self‐reports and proxy reports regarding their QoL. Children with LD, their typically developing peers, their parents and teachers responded to the child, parent, and teacher forms of KINDL^R Questionnaire for Measuring Health‐Related Quality of Life (Ravens‐Sieberer & Bullinger, 1998). Findings showed that children with LD reported significantly lower QoL scores than those reported by typically developing peers. Intraclass correlation coefficients (ICCs) and t‐test results showed that agreement between child reports and parent‐proxy reports was either low or moderate on each QoL dimension. Findings of the study may be used to raise awareness regarding the social and educational needs of children with LD in Turkey.  相似文献   

Mastery motivation,parenting, and school achievement among Hungarian adolescents     

Józsa  Krisztián  Kis  Noémi  Barrett  Karen Caplovitz 《European Journal of Psychology of Education - EJPE》2019,34(2):317-339

European Journal of Psychology of Education - Children’s motivation to master challenging tasks is an important predictor of school success, and yet, such motivation declines during...  相似文献   

The Human Rights Approach to Education in International Organisations     

Klaus Hüfner 《European Journal of Education》2011,46(1):117-126

In this article, the work of three international governmental organisations (IGOs) dealing with human rights will be discussed, namely the United Nations Educational, Scientific and Cultural Organization (UNESCO), the United Nations Children's Fund (UNICEF)¹ and the Council of Europe (CoE). In the first section, the main characteristics of the three IGOs in terms of similarities and differences will be elaborated. Then, their human rights approach to education will be described, dealing with the legal foundations. In the final section, the different strategies of implementation based on both their official mission statements and their present strategy papers will be evaluated under the heading ‘competition vs. cooperation’.  相似文献   

Assessment of leg muscles mechanical capacities: Which jump,loading, and variable type provide the most reliable outcomes?     

Amador García-Ramos  Belén Feriche  Alejandro Pérez-Castilla  Paulino Padial  Slobodan Jaric 《European Journal of Sport Science》2017,17(6):690-698

This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F₀], slope [a], maximum velocity [V₀], and maximum power [P₀]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F₀ [CV: 4.85%, ICC: 0.87], V₀ [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P₀ [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.  相似文献   

Questioning the no-touch discourse in physical education from a children's rights perspective     

Marie Öhman  Ann Quennerstedt 《Sport, Education and Society》2017,22(3):305-320

In this paper we question the rationality of ‘no-touch policies’ and offer an alternative approach to the matter of physical contact between teachers and students in the context of physical education (PE) in schools. Earlier research has drawn attention to how a discourse of child protection is starting to affect how physical contact is viewed in PE practice. The avoidance of intergenerational touch is increasingly justified by referring to the children's rights agenda. Here, arguments for ‘no-touching’ are linked to children's right to be protected from harm. In the paper we explore a children's rights-based viewpoint that supports the use of and need for physical contact in PE teaching by developing theoretical and practice-based arguments. An alternative children's rights perspective, based on rights theorising, is used to formulate the theoretical argument. Interviews with 16 PE teachers about their experiences of physical contact in their pedagogical work form the practice-based arguments. The two arguments provide a way of looking at intergenerational touch in education from the vantage point of children's human right to develop to their full potential, which can support a need for physical touch in pedagogical situations.  相似文献   

Kinematic analysis of the drag flick in field hockey     

Rony Ibrahim  Gert S. Faber  Jaap H. van Dieën 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(1):45-57

Attaining high speed of the stick head and consequently of the ball is essential for successful performance of the drag flick in field hockey, but the coordination pattern used to maximise stick head speed is unknown. The kinematics of the drag flick was studied in ten elite hockey players who performed twenty shots each towards a target located 1.5 m high. A 150 Hz active marker motion analysis system was used, alongside two force plates to detect foot touchdown. Angular velocity and contribution to stick endpoint speed of upper body joints were analysed. Repeated measures ANOVA was used to compare timing of onset and peak angular velocities between joints. Participants used a kinematic pattern that was close to a proximal-to-distal sequence. Trunk axial rotation and lateral rotation towards the target, right wrist flexion and left wrist extension were the main contributors to stick endpoint speed. Coaches should emphasise trunk rotations and wrist flexion and extension movements for maximising stick head speed. Given the high level of the participants in this study, the coordination of joints motions, as reported here, can serve as a guideline for drag flick training.  相似文献   

Sport als Massenveranstaltung     

Prof. Dr. M. Krüger  E. Emrich 《Sportwissenschaft》2010,40(3):161-162

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Erratum to: Metaphysics,prescription and methodological disagreement     

Reutlinger  Alexander  Illari  Phyllis  Hüttemann  Andreas  Frisch  Mathias 《Metascience》2016,25(2):339-339

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