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Marcus Kilpatrick Edward Hebert John Bartholomew Daniel Hollander Daniel Stromberg 《Research quarterly for exercise and sport》2013,84(3):353-359
Purpose: Improvements in motor performance and coordination may be impacted by the interaction of practice and organismic constraints. It has been proposed that these aspects of motor learning are achieved at a different time rate: first, during placement of the events (performance), and second, segmental spatiotemporal relationships (coordination). We focused on the acquisition of the longswing in high bar as one basic skill in gymnastics. The aim of this study was to determine how longswing performance and coordination change to increase swing amplitude as age and expertise increase. Method: One hundred and thirteen male gymnasts were classified into 5 distinct age groups (G1, G2, G3, G4, and G5) on the basis of the national competition rules. Longswing performance (swing amplitude and event placements) and coordination (positive and negative areas in the continuous relative phase) were measured for each group. Results: Analyses of variance revealed that the adequate placement and coordination of the earlier events were achieved in younger groups (G1, G2), while later events and their coordination were accomplished by the older groups (G3 through G5). Conclusion: Our results suggested that the process of longswing acquisition, as age and expertise increase, follows a progression parallel to the temporal occurrence of the task events, instead of the proposed learning sequence of event placement first and then coordination. 相似文献
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A. P. Hollander G. de Groot G. J. van Ingen Schenau H. M. Toussaint H. de Best W. Peeters 《Journal of sports sciences》2013,31(1):21-30
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects’ legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s‐1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s‐1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique. 相似文献
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Sharief Hendricks Tiffany van Niekerk Drew Wade Sin Mike Lambert Steve den Hollander James Brown 《Journal of sports sciences》2018,36(5):522-528
The most frequently occurring contact events in rugby union are the tackle and ruck. The ability repeatedly to engage and win the tackle and ruck has been associated with team success. To win the tackle and ruck, players have to perform specific techniques. These techniques have not been studied at the highest level of rugby union. Therefore, the purpose of this study was to identify technical determinants of tackle and ruck performance at the highest level of rugby union. A total of 4479 tackle and 2914 ruck events were coded for the Six Nations and Championship competitions. Relative risk ratio (RR), the ratio of the probability of an outcome occurring when a characteristic was observed (versus the non-observed characteristic), was determined using multinomial logistic regression. Executing front-on tackles reduced the likelihood of offloads and tackle breaks in both competitions (Six Nations RR 3.0 Behind tackle, 95% confidence interval [95% CI]: 1.9–4.6, effect size [ES] = large, P < 0.001); Championship RR 2.9 Jersey tackle, 95% CI: 1.3–6.4, ES = moderate, P = 0.01). Fending during contact increased the chances of offloading and breaking the tackle in both competitions (Six Nations RR 4.5 Strong, 95% CI: 2.2–9.2, ES = large, P = P < 0.001; Championship RR 5.1 Moderate, 95% CI: 3.5–7.4, ES = large, P < 0.001). For the ruck, actively placing the ball increased the probability of maintaining possession (Six Nations RR 2.2, 95% CI: 1.1–4.3, ES = moderate, P = 0.03); Championship RR 4.0, 95% CI: 1.3–11.8, ES = large, P = 0.01). The techniques identified in this study should be incorporated and emphasised during training to prepare players for competition. Furthermore, these techniques need to be added to coaching manuals for the tackle and ruck. 相似文献
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In a series of 4 studies, we explored preschoolers' understanding of thought bubbles. Very few 3-year-olds or 4-year-olds we tested knew what a thought-bubble depiction was without instruction. But, if simply told that the thought bubble "shows what someone is thinking," the vast majority of 3-year-olds and 4-year-olds easily understood the devices as depicting thoughts generally and individual thought contents specifically. In total, these children used thought-bubble depictions to ascertain the contents of characters' thoughts in a variety of situations; appropriately distinguished such depictions from mere associated actions or objects; described thought bubbles in the language of mental states; judged that persons' thoughts in these depictions were subjective in the sense of person-specific (and hence 2 people can have different thoughts about the same state of affairs); and judged that thought-bubble thoughts ( a ) were representational in the sense of depicting or showing some other state of affairs, ( b ) were mental and thus showed intangible, private, internal thoughts unlike real pictures or photographs, and ( c ) can be false, that is, can depict a person's misrepresentation of some state of affairs. We discuss the implications of these findings for young children's understanding of thoughts and thought bubbles, for their learning and comprehension of pictorial conventions, and for the use of thought bubbles to assess children's early understanding of mind. 相似文献
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This article explores how Indonesian children have integrated media into their daily lives: media ownership at home, media uses, and gratifications sought, are discussed, as is the way in which gender and social-status influence the children–media relationship. Survey data of Jakarta-based children aged 9–15 (N=589) reveal that Indonesian children live in a media saturated environment, with high availability of media platforms in their homes and bedrooms. Similar to children in the US and Europe, children in Jakarta spend considerable amounts of time on a wealth of media platforms and experience multiple gratifications from using multiple media. Gender differences persist in that boys tend to be more into gaming, while girls focus more on communication aspects. High social-status children tend to have more media at their disposal in their bedroom, especially electronic games, computers, and Internet connections. Television is still prominent in the media menu of today, but mobile phones are ready to take its place in the near future. 相似文献
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Sam Hollander 《Publishing Research Quarterly》2011,27(1):26-35
Multimedia EBooks present a tremendous growth opportunity for publishers. Yet, industry executives might be cautious after
witnessing the astounding collapse of the record business during its digital transition over the last 10 years. This article
looks at what went wrong for Big Music, what lessons book publishers can learn from the recording industry’s mistakes and
also some visions of the future. And why digitally, for books—at least—it can’t get here fast enough. 相似文献
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