The influence of shoe drop on the kinematics and kinetics of children tennis players     

Alexis Herbaut  Pascale Chavet  Maxime Roux  Nils Guéguen  Christophe Gillet  Franck Barbier 《European Journal of Sport Science》2016,16(8):1121-1129

This study investigated the immediate effects of reducing the shoe drop (i.e. the difference between the heel and the forefoot height) on the kinematics and kinetics of the lower extremities of children tennis players performing a tennis-specific movement. Thirteen children tennis players performed a series of simulated open stance forehands wearing 3 pairs of shoes differing only in the drop: 0 (D0), 6 (D6) and the control condition of 12?mm (D12). Two embedded forceplates and a motion capture system were used to analyse the ground reaction forces and ankle and knee joint angles and moments of the leading lower limb. In D6 compared with D12, the peak impact force was reduced by 24% (p?=?.004) and the ankle was less dorsiflexed at foot strike (p?=?.037). In D0 compared with D12, the peak impact force was reduced by 17% (p?=?.049), the ankle was less dorsiflexed at foot strike (p?=?.045) and the knee was more flexed at foot strike (p?=?.007). In addition, 4 out of 13 participants (31%) presented a forefoot strike pattern for some of the trials in D0. No difference was observed across shoe conditions for the peak knee extensor moment (p?=?.658) or the peak ankle plantarflexor moment (p?=?.071). The results provide preliminary data supporting the hypothesis that for children tennis players, using a 6-mm lower shoe drop might reduce heel impact forces and thus limit potentially impact-related injuries.  相似文献   

Why extraversion is not enough: the mediating role of initial peer network centrality linking personality to long-term academic performance     

Lisa Thiele  Nils Christian Sauer  Simone Kauffeld 《Higher Education》2018,76(5):789-805

Academic performance (i.e., grade point average) determines career entry factors as well as career success and is thus crucial for students’ future careers. Besides individual factors such as personality traits, individuals’ social embeddedness has been shown to enhance performance. Regarding academic performance, relationships to fellow students (peers), which bundle into one’s developmental network, are a valuable source of psychosocial and career support because occupying central positions within a social network provides the benefit of being able to access career-enhancing resources. Integrating individual and social-contextual factors for the purpose of examining academic performance is therefore plausible. Research results indicate that personality, especially extraversion, might predict performance through network centrality. In this study, we examined this assumption by focusing on extraversion and centrality in the peer developmental network of recently acquainted German psychology bachelor students (N?=?47, 15% male). In a longitudinal design, we analyzed the impact of extraversion and centrality on students’ academic performance at the end of their studies. Results revealed that centrality (i.e., popularity) mediates the relationship of extraversion with academic performance, indicating that extraverted students (regardless of their agreeableness) are more popular among their peers, which, in turn, enhances their academic performance. That is, the likelihood of getting superior final grades depends on whether students manage to attract peers at the very beginning of their university life, which is easier for extraverts. These findings emphasize the importance of the social embeddedness of people, highlight its long-term effects on performance, and yield several implications for research and practice.  相似文献   

Große Fußballspiele — Hochfeste politischer Massen?     

Nils Havemann 《Sportwissenschaft》2007,37(4):394-402

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A roadmap towards improving managed security services from a privacy perspective     

Nils Ulltveit-Moe 《Ethics and Information Technology》2014,16(3):227-240

This paper proposes a roadmap for how privacy leakages from outsourced managed security services using intrusion detection systems can be controlled. The paper first analyses the risk of leaking private or confidential information from signature-based intrusion detection systems. It then discusses how the situation can be improved by developing adequate privacy enforcement methods and privacy leakage metrics in order to control and reduce the leakage of private and confidential information over time. Such metrics should allow for quantifying how much information that is leaking, where these information leakages are, as well as showing what these leakages mean. This includes adding enforcement mechanisms ensuring that operation on sensitive information is transparent and auditable. The data controller or external quality assurance organisations can then verify or certify that the security operation operates in a privacy friendly manner. The roadmap furthermore outlines how privacy-enhanced intrusion detection systems should be implemented by initially providing privacy-enhanced alarm handling and then gradually extending support for privacy enhancing operation to other areas like digital forensics, exchange of threat information and big data analytics based attack detection.  相似文献   

Shoe drop reduction influences the lower limb biomechanics of children tennis players during an open stance forehand: A longitudinal study     

Alexis Herbaut  Emilie Simoneau-Buessinger  Franck Barbier  Christophe Gillet  Maxime Roux  Nils Guéguen 《European Journal of Sport Science》2017,17(10):1261-1269

Compared to traditional tennis shoes, using 0-drop shoes was shown to induce an immediate switch from rear- to forefoot strike pattern to perform an open stance tennis forehand for 30% of children tennis players. The purpose of the study was to examine the long-term effects of a gradual reduction in the shoe drop on the biomechanics of children tennis players performing open stance forehands. Thirty children tennis players participated in 2 laboratory biomechanical test sessions (intermediate: +4 months and final: +8 months) after an inclusion visit where they were randomly assigned to control (CON) or experimental (EXP) group. CON received 12-mm-drop shoes twice, whereas EXP received 8?mm then 4-mm-drop shoes. Strike index indicated that all CON were rearfoot strikers in intermediate and final test sessions. All EXP were rearfoot strikers in intermediate test session, but half the group switched towards a forefoot strike pattern in final test session. This switch resulted in a decreased loading rate of the ground reaction force (?73%, p?=?.005) but increased peak ankle plantarflexors moment (+47%, p?=?.050) and peak ankle power absorption (+107%, p?=?.005) for these participants compared with CON. Biomechanical changes associated with the long-term use of partial minimalist shoes suggest a reduction in heel compressive forces but an increase in Achilles tendon tensile forces.  相似文献   

Kreativität und Bewegung     

Nils Neuber  Christa Kleindienst-Cachay 《Sportwissenschaft》2002,32(4):459-464

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Fußball unterm Hakenkreuz     

Nils Havemann  Michael Krüger 《Sportwissenschaft》2006,36(2):198-202

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What are we to learn from the history of eugenics?     

Nils Roll-Hansen 《Metascience》2013,22(2):387-390

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The Relation between Reading Comprehension and Task‐specific Strategies used in Arithmetical Word Problems     

Nils S⊘vik  Per Frostrad  Mette HEGGBERGET 《Scandinavian Journal of Educational Research》2013,57(4):371-398

The study was concerned with the relation between reading comprehension and task‐specific strategies used in arithmetical word problems. Two hypotheses were formulated in the study. H1 stated that subjects good at arithmetic as well as reading (Group 1) would emphasize deductive strategies to a greater extent than subjects in the remaining groups. H2 considered IQ to be a stronger predictor for subjects’ strategies in arithmetical word tasks than reading comprehension. Four groups of 9‐year‐old children with different competencies in arithmetic and reading were sampled for the investigation. An intelligence test (WISC) and three other tests, Mathematical tests 1‐3, were constructed and administered to the 20 subjects. The tests were used to examine subjects’ strategies in completed task solutions. The findings indicated that great similarities existed between Groups 1 (good at both skills) and 2 (good at arithmetic and poor at reading) as to strategies used in addition and subtraction problems. Whereas subjects in groups 1 and 2 mainly used deductive strategies, those in Groups 3 (good at reading and poor at arithmetic) and 4 (poor at both skills) rather used procedural strategies in solving the problems. Concerning strategies applied in multiplication and division tasks a more diverse pattern of strategies was revealed in all of the four groups, but the majority of subjects emphasized deductive strategies. Multiple regression analyses of the data indicated strong linear relationships between the predictors and the criteria used in the analyses. However, IQ was the only significant single predictor found in the regression analyses. H1 had to be suspended, but H2 could not be rejected.  相似文献   

Role of Significant Life Experiences in Building Environmental Knowledge and Behavior Among Middle School Students     

Kathryn T. Stevenson  M. Nils Peterson  Sarah J. Carrier  Renee L. Strnad  Howard D. Bondell  Terri Kirby-Hathaway 《The Journal of environmental education》2013,44(3):163-177

Significant life experience research suggests that the presence of role models, time outdoors, and nature-related media foster pro-environmental behavior, but most research is qualitative. Based on a random sample of middle school students in North Carolina, USA, we found limited positive associations between presence of a role model and time outdoors with behavior and a negative association between watching nature television and environmental knowledge. The strongest predictors of environmental knowledge and behavior were student/teacher ratio and county income levels, respectively. We also found that Native Americans engaged in environmental behaviors more than Caucasians, and that African American and Hispanic students had lower levels of environmental knowledge. Accordingly, life experiences appear less important than promoting small class sizes and addressing challenges associated with lower incomes in schools.  相似文献