Information-governing dynamics of attacker–defender interactions in youth rugby union

Abstract

Previous work on dynamics of interpersonal interactions in 1 vs. 1 sub-phases of basketball has identified changes in interpersonal distance between an attacker and defender as a potential control parameter for influencing organizational states of attacker–defender dyads. Other studies have reported the constraining effect of relative velocity between an attacker and defender in 1 vs. 1 dyads. To evaluate the relationship between these candidate control parameters, we compared the impact of both interpersonal distance and relative velocity on the pattern-forming dynamics of attacker–defender dyads in the sport of rugby union. Results revealed that when interpersonal distance achieved a critical value of less than 4 m, and relative velocity values increased or were maintained above 1 m · s^?1, a successful outcome (i.e. clean attempt) for an attacker was predicted. Alternatively, when values of relative velocity suddenly decreased below this threshold, at the same critical value of interpersonal distance, a successful outcome for the defender was predicted. Data demonstrated how the coupling of these two potential, nested control parameters moved the dyadic system to phase transitions, characterized as a try or a tackle. Observations suggested that relative velocity increased its influence on the organization of attacker–defender dyads in rugby union over time as spatial proximity to the try line increased.     

Improvement of cellular health indicators and muscle quality in older women with different resistance training volumes

ABSTRACT

The main purpose of this study was to compare the effects of resistance training (RT) performed with different training volumes on phase angle (PhA), body water components, and muscle quality (MQ) in untrained older adult women. A second purpose was to assess the relationship between PhA and MQ. Sixty-two older adult women (68.6 ± 5.0 years, 65.2 ± 13.3 kg, 156.1 ± 6.2 cm) were randomly assigned into one of the three groups: two training groups performed either 1 set (G1S) or 3 sets (G3S), or a control group (CG). Body water components and PhA were estimated by bioelectrical impedance (BIA). MQ was determined by dividing skeletal muscle mass estimated by dual-energy absorptiometry (DXA) by total muscle strength from three exercises. After the intervention period, both training groups demonstrated improvements (P < 0.05) when compared with CON for intracellular water, total body water, PhA, and MQ. These results suggest that RT can improve PhA, body water components, and MQ after 12 weeks of RT in untrained older women, regardless of training volume. Furthermore, changes in MQ were positively correlated with changes in PhA (r = 0.60, P < 0.01).     

Parallel assessment of nutrition and activity in athletes: Validation against doubly labelled water, 24-h urea excretion,and indirect calorimetry

Abstract

The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal · day^?1). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g · kg^?1 · day^?1). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal · day^?1) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal · min^?1; cycling: r = 0.95, SEE = 1.4 kcal · min^?1). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes.     

‘Strong mothers make strong children’: sports,eugenics and nationalism in Brazil at the beginning of the twentieth century

Based on post-structural feminist and gender studies, the present article analyses the importance given to the practice of physical education, sports and exercise as part of the national policy to strengthen the Caucasian-Brazilian population at the beginning of the twentieth century, emphasising the priority made of the White female body as the most important instrument in strengthening the so called ‘White race’. All the editions of the Revista Educação Physica, the first magazine published specifically for physical education and sport in Brazil, was the primary research source. Other books, manuals, reviews from scientific congresses and official publications from the Brazilian Government at the time were also examined. Via the technical analysis of the contents of the aforementioned publications, it was possible to conclude that the Brazilian nationalist discourse at the time sought what was called the ‘refinement of the White race’ by strengthening its women while, at the same time, systematically ignoring Black women.     

Is passive drag dependent on the interaction of kayak design and paddler weight in flat-water kayaking?

Abstract

Drag is one of the major factors that influences kayaking performance. To focus on the drag of the kayak’s hull shape and the paddlers’ weight per se, the passive drag (D_p) was measured on a flat-water sprint course for one paddler with added weights. D_p was measured by an electromechanical towing device using a load cell, at incremental and constant velocities from 2.78 to 5.56 m/s. Three kayaks of different sizes and shapes (Nelo® K1 Quattro-M, ML, and L) were used and the paddlers’ body weight was adjusted with weights so the total paddler weight in the kayak was 65, 75, and 85 kg. The mean D_p increased by the power function of D = kvⁿ (mean R² = .990; SD .006). The D_p went from 21.37?±?1.29 N at 2.78 m/s to 89.32?±?6.43 N at 5.56 m/s. For the two lighter weighted kayaks (65 and 75 kg), the lowest D_p was observed with different kayak sizes (M, ML, or L) depending on the target velocity. The manufacturers suggest that paddlers should select a kayak size according to their body weight to minimise drag; however, the results of this study suggest that target velocities, and thus competition distance should also be factored into kayak selection.     

Communicating the new chemistry in 18th-century Portugal: Seabra’s Elementos de Chimica

In this paper, we analyse the aims, contents and impact of Seabra’s two-volume textbook – Elementos de Chimica (Elements of Chemistry) – published in 1788 and 1790. Seabra’s Elements of Chemistry does not conform to the characteristics usually ascribed to textbooks by traditional historiography, and in particular to textbooks published in the peripheries. Marking the arrival of the new chemistry in Portugal, in a period in which many still resisted Lavoisier’s chemistry, this textbook was a state of the art account written in Portuguese, interspersed with critical evaluations, original comments and novel contributions. Despite being the only Portuguese chemistry textbook written during this period, it had hardly any readers, even among its natural audience at the University of Coimbra.     

An instructional model for web-based e-learning education with a blended learning process approach

Web‐based e‐learning education research and development now focuses on the inclusion of new technological features and the exploration of software standards. However, far less effort is going into finding solutions to psychopedagogical problems in this new educational category. This paper proposes a psychopedagogical instructional model based on content structure, the latest research into information processing psychology and social contructivism, and defines a blended approach to the learning process. Technologically speaking, the instructional model is supported by learning objects, a concept inherited from the object‐oriented paradigm.     

History of education in Brazil: the construction of a knowledge field

This article analyses the general characteristics of the construction of the field of history of education in Brazil. To do so, it highlights the existing historiography and aims to describe the process of institutionalisation of this knowledge field, which, in general terms, has been focused on the area of teacher training. Since the nineteenth century, however, it has also been possible to identify systematic historiographical efforts in Brazil that are not directly related to the school system, but rather to the teaching of and research into the history of education within Brazilian universities. The article addresses the organisation of the field, the ways in which it has been structured and the strategies of academic legitimisation employed to achieve this. These include the regular production of dissertations and doctoral theses, the publication of books and journals, academic events and the creation of research groups and scientific associations, through which research findings have found national and international circulation. This set of indicators creates conditions for an understanding of the expansion and reconfiguration of the field of history of education that began in the 1980s, as well as of the challenges this phenomenon presents to current historiography and teacher training in Brazil.