The relationship between peak height velocity and physical performance in youth soccer players

Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 +/- 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 +/- 1.5 cm x year-1, 8.4 +/- 3.0 kg x year-1 and 13.8 +/- 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time.     

The energetics and benefit of an arm swing in submaximal and maximal vertical jump performance

The aims of this study were to investigate the energy build-up and dissipation mechanisms associated with using an arm swing in submaximal and maximal vertical jumping and to establish the energy benefit of this arm swing. Twenty adult males were asked to perform a series of submaximal and maximal vertical jumps while using an arm swing. Force, motion and electromyographic data were recorded during each performance and used to compute a range of kinematic and kinetic variables, including ankle, knee, hip, shoulder and elbow joint powers and work done. It was found that the energy benefit of using an arm swing appears to be closely related to the maximum kinetic energy of the arms during their downswing, and increases as jump height increases. As jump height increases, energy in the arms is built up by a greater range of motion at the shoulder and greater effort of the shoulder and elbow muscles but, as jump height approaches maximum, these sources are supplemented by energy supplied by the trunk due to its earlier extension in the movement. The kinetic energy developed by the arms is used to increase their potential energy at take-off but also to store and return energy from the lower limbs and to "pull" on the rest of the body. These latter two mechanisms become more important as jump height increases with the pull being the more important of the two. We conclude that an arm swing contributes to jump performance in submaximal as well as maximal jumping but the energy generation and dissipation sources change as performance approaches maximum.     

Known-item Searches Resulting in Zero Hits: Considerations for Discovery Systems

The goal of this article is to understand the reasons why known-item search queries entered in a discovery system return zero hits. We analyze a sample of 708 known-item queries and classify them into four categories of zero hits with regard to whether the item is held by the library and whether the query is formulated correctly: (1) item in stock, but query incorrect, (2) item not in stock, (3) item in stock, but incomplete or erroneous metadata, (4) query is ambiguous or not understandable. The main reasons for zero hits are caused by acquisition and erroneous search queries. We discuss possible solutions for known-item queries resulting in zero hits from the side of the system and show that 30% of zero hits could easily be avoided by applying automatic spelling correction. We argue that libraries can improve their discovery systems or online catalogs by applying strategies to avoid or cope with zero hits inspired by web search engines and commercial search web sites.     

Wider die „Sternchenkunde“!

In general, empirical results are analyzed using statistical methods to examine and discuss differences and interrelationships. Statistical methodological evaluation and the underlying reporting strategy can be described as a technical language that has to be learnt for successful communication between researchers, authors and reviewers; however, empirical science is a constantly changing environment which is why the statistical methods applied have to be refined to adhere to new empirical approaches. This line of thought will be discussed in this article and five essential recommendations will be presented: (a) directionality of hypotheses, (b) confidence intervals, (c) effect sizes, (d) confidence intervals of effect sizes and (e) practical meaningfulness.     

Predictive value of coaches’ early technical and tactical notational analyses on long-term success of female handball players

ABSTRACT

Despite the importance of technique and tactics for athlete performance, there has been surprisingly little research on the value of these skills in talent identification and development. This study investigated the relationship between coaches’ early notational analyses of female youth handball players and the long-term success of these athletes. Participants included sixty-eight female handball players involved in a talent selection camp in Germany when they were between 12 and 14 years of age (mean = 14.42, SD = 0.42). All subsequently ended up as non-, semi- or professional adult players. During the initial selection camp, participants were evaluated on a range of quantitative and qualitative measures of technical and tactical skill. Results indicated significant differences between the groups, but only for the number of actions taken, not for the quality of those actions. While this seems counterintuitive, it may reflect the likelihood that more skilled and/or talented players take more actions. Further work is necessary to explore the validity and implications of these findings.     

A longitudinal perspective on inductive reasoning tasks. Illuminating the probability of change

Cognitive scientists have studied internal cognitive structures, processes, and systems for decades in order to understand how they function in human learning. Nevertheless, questions concerning the diagnosis of changes in these cognitive structures while solving inductive reasoning tasks are still being scrutinized. This paper reports findings from an experimental study in which 64 participants in three experimental groups solved tasks at ten measurement points. We were able to illuminate changes of cognitive structures and found significant differences between the treatments. The results also indicate that supportive information is an important aid for developing cognitive structures while solving inductive reasoning tasks.     

Professors as value agents: a typology of management academics’ value structures

The paper addresses the paradox of value-free science and the need for value-oriented management education. Taking the values discussion in the German management community as an example, we identify two stereotypes in management literature: an allegedly value-free scientist who limits responsibility to economic aims and a value-laden academic who accepts responsibilities for societal aims and who aims to influence students’ values. These stereotypes are then challenged against empirical data from a global survey of management academics. While the stereotypes are shown to be of only limited relevance, five clusters of management academics are identified based on their economic values, their social values and their intention to influence their students’ values. As determinants of cluster attribution, cultural environment and discipline prove the most influential on value differences in the global sample. Gender, in contrast, has no significant impact. Finally, implications for higher education institutions are derived that may help to cope with values more consciously and more professionally.