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

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.     

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

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.     

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

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.     

A roadmap towards improving managed security services from a privacy perspective

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.     

China's recruitment of African university students: policy efficacy and unintended outcomes

This article explores how Sino-African relations are affected by the growing number of Africans who pursue higher education in China. China actively recruits African university students in order to increase soft power and generate income from the export of education services. Semi-structured interviews with African university students suggest that China fails to reach these policy objectives because the students are disappointed with the quality of the education they receive. However, the students engage in trade and contribute to the fast-growing export of Chinese products to African markets, thereby reinforcing the ties between China and Africa in unintended ways.     

Positive environments in youth football

Derived from Basic Psychological Needs Theory (BPNT) is the notion that the social environment may promote athletes’ basic psychological needs, which are considered important for positive development and optimal motivational functioning. The present study investigated the predictive value of perceived justice and coach feedback on basic needs satisfaction in the context of youth football. Participants were Norwegian youth football players (N?=?532) participating in a national tournament. During the initial stage of the tournament, players completed the Coaching Feedback Questionnaire, Perceived Justice in Sport Questionnaire and Basic Psychological Needs in Exercise Scale under supervision. Regression analysis showed that perceived justice and positive/instructive coaching feedback positively predicted players’ needs satisfaction, while negative feedback and non-reinforcement/ignoring mistakes were not significant predictors of needs satisfaction. Together, perceptions of justice and coach feedback explained 24% of the variance in athletes’ needs satisfaction. The findings thereby indicate that athletes’ perceptions of fairness and coach feedback are important in understanding youth athletes’ needs satisfaction.