Age-related differences in repeated-sprint ability in highly trained youth football players

Abstract

In this study, we investigated the age-related differences in repeated-sprint ability and blood lactate responses in 134 youth football players. Players from the development programme of a professional club were grouped according to their respective under-age team (U-11 to U-18). Following familiarization, the participants performed a repeated-sprint ability test [6 × 30-m sprints 30 s apart, with active recovery (2.0–2.2 m · s^?1) between sprints]. The test variables were total time, percent sprint decrement, and post-test peak lactate concentration. Total time improved from the U-11 to U-15 age groups (range 33.15 ± 1.84 vs. 27.25 ± 0.82 s), whereas no further significant improvements were evident from U-15 to U-18. No significant differences in percent sprint decrement were reported among groups (range 4.0 ± 1.0% to 5.5 ± 2.1%). Post-test peak lactate increased from one age group to the next (range 7.3 ± 1.8 to 12.6 ± 1.6 mmol · l^?1), but remained constant when adjusted for age-related difference in body mass. Peak lactate concentration was moderately correlated with sprint time (r = 0.70, P > 0.001). Our results suggest that performance in repeated-sprint ability improves during maturation of highly trained youth football players, although a plateau occurs from 15 years of age. In contrast to expectations based on previous suggestions, percent sprint decrement during repeated sprints did not deteriorate with age.     

Prediction of adult height in girls: The Beunen-Malina-Freitas method

Abstract

The purpose of this study was to validate and cross-validate the Beunen-Malina-Freitas method for non-invasive prediction of adult height in girls. A sample of 420 girls aged 10–15 years from the Madeira Growth Study were measured at yearly intervals and then 8 years later. Anthropometric dimensions (lengths, breadths, circumferences, and skinfolds) were measured; skeletal age was assessed using the Tanner-Whitehouse 3 method and menarcheal status (present or absent) was recorded. Adult height was measured and predicted using stepwise, forward, and maximum R ² regression techniques. Multiple correlations, mean differences, standard errors of prediction, and error boundaries were calculated. A sample of the Leuven Longitudinal Twin Study was used to cross-validate the regressions. Age-specific coefficients of determination (R ²) between predicted and measured adult height varied between 0.57 and 0.96, while standard errors of prediction varied between 1.1 and 3.9 cm. The cross-validation confirmed the validity of the Beunen-Malina-Freitas method in girls aged 12–15 years, but at lower ages the cross-validation was less consistent. We conclude that the Beunen-Malina-Freitas method is valid for the prediction of adult height in girls aged 12–15 years. It is applicable to European populations or populations of European ancestry.     

Effect of different inter-repetition rest intervals across four load intensities on velocity loss and blood lactate concentration during full squat exercise

ABSTRACT

This study aimed to analyze the acute effect of inter-repetition rest (IRR) intervals on mechanical and metabolic response during four resistance exercise protocols (REPs). Thirty resistance-trained men were randomly assigned to: continuous repetitions (CR), 10 s (IRR10) or 20 s (IRR20) inter-repetition rest. The REPs consisted of 3 sets of 6, 5, 4 and 3 repetitions against 60, 70, 75 and 80% 1RM, respectively, in the full squat exercise. Muscle fatigue was assessed using: percentage of velocity loss over three sets, percentage of velocity loss against the ~1 m·s^?1 load (V1 m·s^?1), and loss of countermovement jump (CMJ) height pre-post exercise. Blood lactate was measured before and after exercise. The percentage of velocity loss over three sets and lactate concentration were significantly lower (P < 0.05) for IRR groups compared to CR in all REPs. The CR group showed a significantly higher (P < 0.05) velocity loss against V1 m·s^?1 load and loss of CMJ height pre-post exercise than IRR groups in REP against 60% 1RM. In conclusion, both IRR groups produced a significant lower degree of fatigue compared to CR group. However, no significant differences were found in any measured variables between IRR configurations.     

Relationships between intrinsic motivation, physical self-concept and satisfaction with life: a longitudinal study

In this study, we examined the relationships between intrinsic motivation, physical self-concept, and satisfaction with life using cross-lagged panel models analysed via structural equation models. The sample consisted of 293 participants (148 men, 145 women) aged 18-70 years who performed diverse types of physical exercise. Three alternative models were tested. The data were better represented by a model in which physical self-concept mediates the relationships between intrinsic motivation and satisfaction with life. Specifically, the direct effects of intrinsic motivation on physical self-concept, and of physical self-concept on satisfaction with life were significant, with the amount of explained variance increasing over time. In conclusion, people who perform physical exercise regularly, and who have fun over time will tend to have a better physical self-perception and, consequently, more psychological well-being.     

Contribution of historical Spanish inventions to the knowledge of olive oil industrial heritage

This article presents new research, which has the objective of quantifying the knowledge produced by historical technological innovations in the field of olive oil industrial heritage. It studies inventions related to the mechanical processes of the extraction of olive oil between 1826 and 1966, which are recorded in the Historical Archive of the Spanish Patent and Trademark Office. It uses a new adaptation of the methodology of knowledge management (KM) defined by Nonaka and Takeuchi. We have obtained the knowledge value of each innovation according to the level of technological knowledge registered at the time, while distinguishing between the historical evolution of inventions relating to milling and those relating to pressing. In the first analysis, the results show a recession in the quantitative level of knowledge in the olive oil sector with respect to the technological potential of the time. However, when contrasted with the events relating to industrial heritage at the time, it is possible to account for this technological evolution and prove the validity of the methodology used. The results show that general evolution of the knowledge generated has decreased, particularly in the pressing process, although this is not the case in the milling process.     

Externally Funded Research in Counselor Education: An Overview of the Process

“Publish or perish” is a phrase familiar to untenured and tenured faculty alike. In recent years, prominence has been placed on academicians to secure external funding for their research and training projects. The counselor education field has not been immune to this call for externally funded projects. This article includes strategies for seeking and receiving external funding for counseling‐related research in an effort to help counselor educators flourish in a paradigm that increasingly calls for greater external funding. Emphasis is placed on gaining knowledge and experience with federal funding agencies.     

AIDA: An integrated authoring environment for educational software

This paper describes an integrated authoring environment, AIDA (Ambiente Integrado de Desenvolvimento de Aplicações educacionais). It is an open tool, giving the author a high degree of freedom both in package characteristics and design methodologies used. This environment integrates several modules. The core of the design module is a prototyping tool, allowing the creation of evolutionary prototypes. These prototypes can include several types of multimedia components and can be used as part of the final package. The AIDA environment also includes other options that support evaluation, learning materials re-use, communication between authoring team members and translation and cultural adaptation of packages to work in different environments. An experimental version of this authoring environment was implemented and the results of its evaluation are encouraging. In this paper we also present an example of a package created with the AIDA authoring environment.     

Creating a dialogic environment for transformative science teaching practices: towards an inclusive education for science

Abstract

This paper focuses on the design and application of a teacher training strategy to promote the inclusive education of students with disabilities in the science classroom, through the creation of adult learning environments grounded on the principles of dialogic learning. Participants of the workshop proposal consisted of a group of twelve teachers who were working at various educational levels. Teacher teams proposed and implemented in their classroom, innovative, inclusive science-learning activities about a topic of their choice. Data were collected from interviews with teachers five months after the courses, teachers’ portfolios about their practice during implementation of such sequences, and researchers’ observations. The data suggest that it is possible to stimulate a gradual transformation of teaching practices through a teacher training proposal that promotes self-awareness and critical reflection, situated in the creation of meaning and a willingness to change in the spirit of solidarity and social action. We found elements to recommend the incorporation of these innovations at the curricular and practical level for teacher training schools and for in-service teacher development programmes in Mexico and elsewhere.     

Memorisation methods in science education: tactics to improve the teaching and learning practice

How can science teachers support students in developing an appropriate declarative knowledge base for solving problems? This article focuses on the question whether the development of students’ memory of scientific propositions is better served by writing propositions down on paper or by making drawings of propositions either by silent or muttering rehearsal. By means of a memorisation experiment with eighth- and ninth-grade students, we answer this question. In this experiment, students received instruction to memorise nine science propositions and to reproduce them afterwards. To support memorisation students were randomly assigned either to a group that received instruction to write each proposition on paper or to a group that received instruction to make a drawing about the content of the proposition. In addition, half of the students in both groups received instruction to mutter and the other half of them received instruction to write or draw in silence. The main conclusion from the experiment is that after four weeks students who had made a drawing remembered significantly more propositions than those who had memorised the propositions by writing them down. Our research further revealed that it did not matter whether students muttered or memorised silently.