Caffeine supplementation does not affect match activities and fatigue resistance during match play in young football players

Abstract

The study examined the effect of caffeine supplementation on match activities and development of fatigue during a football match. In a randomised, double-blind cross-over design, two experimental football games separated by 7 days were organised between the junior teams of two professional football clubs (17.6 ± 1.1 years (±s), 71.7 ± 6.9 kg, 13.9% ± 5.0% body fat). The players ingested either a capsule of 6 mg · kg^?1 b.w. caffeine or placebo (dextrose) 65 min prior to the matches. Match activities were assessed using the ZXY match analysis system, and a Yo-Yo intermittent recovery test–level 2 (Yo-Yo IR2) was conducted immediately post-game. Heart rate was monitored throughout the game, and blood samples were obtained at baseline, half-time and after the game. There were no differences between caffeine and placebo regarding total distance covered (10,062 ± 916 vs 9854 ± 901 m), high-intensity running (557 ± 178 vs 642 ± 240 m), sprinting distance (109 ± 58 vs 112 ± 69 m) or acceleration counts (123 ± 31 vs 126 ± 24). In both trials, players displayed lower (P < 0.05) values in total distance and acceleration counts in the last 15 min compared to all other 15-min periods of the matches. Post-game Yo-Yo IR2 performance was not different between game trials (caffeine: 829 ± 322 m; placebo 819 ± 289 m). In conclusion, oral caffeine administration does not appear to have an ergogenic effect in young football players during match play.     

Analysis and design of quadratic parameter varying (QPV) control systems with polytopic attractive region

This paper proposes a gain-scheduling approach for systems with a quadratic structure. Both the stability analysis and the state-feedback controller design problems are considered for quadratic parameter varying (QPV) systems. The developed approach assesses/enforces the belonging of a polytopic region of the state space to the region of attraction of the origin, and relies on a linear matrix inequality (LMI) feasibility problem. The main characteristics of the proposed approach are illustrated by means of examples, which confirm the validity of the theoretical results.     

Measuring STEM students’ mathematical identities

Studies on identity in general and mathematical identity in particular have gained much interest over the last decades. However, although measurements have been proven to be potent tools in many scientific fields, a lack of consensus on ontological, epistemological, and methodological issues has complicated measurements of mathematical identities. Specifically, most studies conceptualise mathematical identity as something multidimensional and situated, which obviously complicates measurement, since these aspects violate basic requirements of measurement. However, most concepts that are measured in scientific work are both multidimensional and situated, even in physics. In effect, these concepts are being conceptualised as sufficiently uni-dimensional and invariant for measures to be meaningful. We assert that if the same judgements were to be made regarding mathematical identity, that is, whether identity can be measured with one instrument alone, whether one needs multiple instruments, or whether measurement is meaningless, it would be necessary to know how much of the multidimensionality can be captured by one measure and how situated mathematical identity is. Accordingly, this paper proposes a theoretical perspective on mathematical identity that is consistent with basic requirements of measurement. Moreover, characteristics of students’ mathematical identities are presented and the problem of “situatedness” is discussed.     

Openness in Adoption and the Level of Child Participation

There is great controversy regarding the impact of openness in adoption, especially the impact of such an arrangement on adopted children. Three indicators of the level of child participation in the openness arrangement were examined: ( a ) level of openness reported by adoptive parents, ( b ) level of information adopted children reported having about their birthparents, and ( c ) whether adoptive parents have withheld any pertinent information gained through communication with the birthmother from the adopted child. 171 children (90 males, 81 females; mean age = 7.99) were studied to assess how that participation influenced their conceptual understanding of what adoption means, general self-worth, satisfaction with level of openness, and curiosity about birthparents. Overall it does not appear that providing information about a child's birthparents will confuse the child about the meaning of adoption or lower the child's self-esteem, but neither will it move them to levels of understanding that are beyond their cognitive capabilities to reach.     

Academic vocabulary and reading comprehension: exploring the relationships across measures of vocabulary knowledge

Reading and Writing - This study examined the relationship between knowledge of academic vocabulary and reading comprehension in data contributed by 5855 middle school students. Each student...     

In Search of Journalism Funding

Digitization has caused disruption in the traditional business model of the news media. Policy implementation in the media sector is therefore increasingly raised as an economic question, involving concern for the ability of legacy media to serve as independent platforms for public deliberation. While media policy traditionally tends to focus on unwanted developments (i.e. local monopolies, ownership concentration, etc.), the side-effect often representing an obstacle to innovation, the question is how future media policy should account for innovation needs. Combining media economics, policy analysis and strategic management theory, this article combines interviews with key stakeholders with policy document analysis to a scenario analysis of possible future policy directions enabling innovation in the news industries in Norway.     

COMMENTARY: Sports Broadcasting: Is it a Job for Public Service Broadcasters?-A Welfare Economic Perspective

The current policy of European public service broadcasters (PSBs) of acquiring expensive sports rights does not correspond with welfare economic principles. The Listed Events regulation prevents sports events of major importance for society from migrating to pay-TV broadcasters. Handing over expensive sports programs to commercial rivals will release resources that can be used on other activities, including programs that have characteristics of externalities and merit goods. Such a policy has been adopted by Australian PSBs.     

Finding the optimal guidance for enhancing anchored instruction

This study investigated the effect of different methods of guidance with anchored instruction on students' mathematical problem-solving performance. The purpose of this research was to iteratively design a learning environment to find the optimal level of guidance. Two iterations of the software were compared. The first iteration used explicit instruction upfront followed by practice problems, and the second iteration provided structured problem-solving guidance as needed to solve the problems within the software. Pilot testing was conducted with 32 fifth-grade students from two inclusive classrooms observed a year apart within a small Midwestern, urban school. A parametric analysis of covariance was used to compare the problem-solving performance of the students who used the two different iterations. Enhancing anchored instruction with structured problem-solving guidance on an as-needed basis significantly improved students' problem-solving performance on conceptually easy problems, but not for more complex problems. The implications of this research illustrate the importance of iteratively designing and developing learning environments to take into consideration the needs of a particular situation.