Dribbling speed along curved paths predicts attacking performance in match-realistic one vs. one soccer games

This study assessed whether a new, closed-skill dribbling or sprinting task could predict attacking performance in soccer. Twenty-five male players were recruited from the Londrina Junior Team Football Academy in Brazil and asked to either dribble the ball or sprint through five custom circuits that varied in average curvature (0–1.37 radians.m^?1). These measures were then validated using a realistic one vs. one competition in which each player acted as attacker or defender in turn (N = 1330 bouts). Sprinting (ICC = 0.96) and dribbling (ICC = 0.97) performances were highly repeatable for individual players. Average dribbling speed decreased non-linearly with increasing circuit curvature (F = 239.5; P < 0.001) from 5.19 ± 0.11 ms^?1 on the straightest path to 2.13 ± 0.03 ms^?1 on the curviest. Overall, dribbling but not sprinting performance predicted attacking success in the one vs. one competition, explaining more than 50% of the variation in attacking success alone (r_p = 0.70; P < 0.001). In conclusion, our new closed-skill dribbling assessment is a valid and reliable protocol to predict a soccer player’s success in attacking performance in one vs. one situation, and can be used to identify talented players.     

Effect of resistance training with different frequencies and subsequent detraining on muscle mass and appendicular lean soft tissue,IGF-1, and testosterone in older women

Objective: To analyse the effect of resistance training (RT) frequency on muscle mass, appendicular lean soft tissue, insulin-like growth factor 1 (IGF-1), testosterone, and their changes with detraining in older women. Methods: Forty-five physically independent older women (≥ 60?years) were randomly assigned to perform RT either two (G2X, n = 21) or three times/week (G3X, n = 24), during 12?weeks (8 exercises, 1 set of 10–15 repetition maximum). Muscle mass and appendicular lean soft tissue, IGF-1, testosterone, and dietary intake were measured at pre-training, post-training, and after detraining (12?weeks). Results: Muscle mass and appendicular lean soft tissue significantly increased post-training (G2X?=?+5.5% and G3X?=?+5.8%, P?P?P?Conclusion: We conclude that lower RT frequency is as effective as higher frequency to improve muscle mass and appendicular lean soft tissue, and to maintain testosterone and IGF-1. Additionally, detraining may reduce testosterone regardless of RT frequency. These results are specifically for community-dwelling older women and may not be generalized to other populations.     

The evolution of student-coach’s pedagogical content knowledge in a combined use of sport education and the step-game-approach model*

Background: One of the essential elements within Sport Education is the inclusion of student roles and responsibilities. While previous research has examined students’ performance in officiating tasks, the examination of student-coaches’ pedagogical content knowledge (PCK) within peer-assisted tasks of Sport Education has been scarce. Indeed, the only study to date which has examined student-coach effectiveness was conducted by Wallhead and O’Sullivan [2007. “A Didactic Analysis of Content Development During the Peer Teaching Tasks of a Sport Education Season.”Physical Education and Sport Pedagogy 12 (3): 225–243]. In that study, student-coaches struggled to manifest PCK by providing appropriate demonstrations, to diagnose errors, or to modify tasks for higher order content development. The study of PCK may be a useful heuristic to examine instructional effectiveness in physical education.

Purpose: The purpose of this study was to examine the evolution of the PCK of a cohort of student-coaches across three hybrid Sport Education-Step Game Approach seasons, and to examine the impact of protocols put in place to specifically enhance coaches’ PCK.

Participants and setting: Twenty-one students and one teacher from a school class in the north of Portugal participated in the present study.

Method: Data from multiple sources were collected: (a) videotape observations of all lessons, (b) field notes, and (c) pre-lesson interviews with the student-coaches. These were then subjected to deductive examination through a process of thematic analysis.

Findings and conclusions: Following a baseline season that identified four key limitations within the student-coaches’ instruction (task presentation, error diagnosis, feedback, and task modification), these students participated in specific coach preparation that involved modelling teacher’s instruction, pre-lesson meetings, and coaches’ corners. While showing marked improvement in their content knowledge across the second season, a second protocol was instigated during the third that involved the student-coaches to participate in stimulated reflections of their instruction and the incorporation of planning sheets to enhance their instruction. It was found that both interventions were efficacious in developing student-coaches’ PCK, which allowed a more complete transfer of the instructional responsibility from the teacher to the students. These results give insight into the importance of including coach education protocols within the design of seasons of Sport Education with respect to student-coaches’ instructional preparation.     

Analysis of the distances covered and technical actions performed by professional tennis players during official matches

The purpose of this study was to analyse the physical and technical performances of professional tennis players during official matches. The trajectories of eight players were obtained during matches, using an automatic tracking method. The distances covered and technical performances were analysed for the first and second sets. The athletes covered (mean ± standard deviation) a total of 1702.4 ± 448.2 m in the first set, 1457.6 ± 678.1 m in the second set and 3160.0 ± 880.1 in the entire match. No differences were found between the sets for the physical variables (lateral and forward displacements, distance covered per rally, per game and per set, and the percentage of time spent in each range of velocity). However, the distances covered by the athletes during the rallies in which they were serving (median = 5.2; interquartile range (IQR) = 6.7 m) were statistically smaller than when they were returning (median = 6.2; IQR = 7.7 m). Forehand ground stroke proficiency decreased from the first (mean ± standard deviation: 75.2 ± 4.11%) to the second set (mean ± standard deviation = 65.5 ± 14.3%). In conclusion, tennis players did not present reduced physical performance from the first to the second set.     

Bar velocities capable of optimising the muscle power in strength-power exercises

This study aimed at testing whether there are mean propulsive velocities (MPVs) capable of maximising the mean propulsive power (MPP) during the execution of bench press (BP), bench throw (BT), half squat (HS) and jump squat (JS). Additionally, we assessed the differences in MPP/MPV between ballistic and traditional exercises. Seventeen male rugby sevens players performed MPP tests in BP, BT, HS and JS and maximum isometric force (MIF) tests in HS and BP. The JS presented higher MPP (977.4 ± 156.2 W) than the HS (897.9 ± 157.7 W) (P < 0.05); the BP (743.4 ± 100.1 W) presented higher MPP than the BT (697.8 ± 70.4 W) (P < 0.05). Ballistic exercises presented higher optimum MPV (JS = 1.02 ± 0.07 m·s^?1; BT = 1.67 ± 0.15 m·s^?1) than traditional exercises (HS = 0.93 ± 0.08 m·s^?1; BP = 1.40 ± 0.13 m·s^?1) (P < 0.05). The optimum MPP in the JS, BT, HS and BP occurred at 28.2 ± 5.79, 23.3 ± 4.24, 32.4 ± 9.46 and 27.7 ± 5.33% of the MIF, respectively. The coefficient of variation (CV) of MPV at optimum MPP ranged from 7.4% to 9.7%, while the CV of %MIF ranged from 18.2% to 29.2%. The MPV is a more precise indicator of the optimum loads than the percentages of MIF due to its low inter-subject variability as expressed by CV. Therefore, MPV can be used to determine the optimum power load in the four investigated exercises.     

Nonlinear modeling and robust LMI fuzzy control of overhead crane systems

Overhead cranes are widely used structures for lifting and conveying heavy loads. The development of feedback control systems for such equipment is important due to the large number of potential applications and advantages over manual operation concerning stability and robustness. This paper aims to represent the key nonlinear dynamics of crane systems by means of a state-space fuzzy model with compact rule-base structure. The fuzzy model is useful to assist the design of a fuzzy controller based on the concept of parallel compensation. A well-posed conservative linear-matrix-inequality (LMI) feasibility problem is formulated so that a solution guarantees closed-loop Lyapunov stability, bounded control inputs, quick positioning of the supporting cart, and suppression of load oscillations and collisions. The fuzzy controller is composed by rules with linear control laws derived from local state-space models. The controller warrants asymptotic convergence of the states. Due to the nonlinear nature of the fuzzy model and controller, Jacobian linearization is avoided. The proposed fuzzy control approach for cranes has shown to be more effective and robust than an optimal quadratic controller, and able to move cargo smoothly and safely to a destination. Particularly, constrained and smoother control inputs avoid actuator saturation, and tend to increase its lifetime. Laboratory experiments using the LMI fuzzy controller and actual data validates the approach for cranes in actual scenario.     

Unfairness in access to higher education: a 11 year comparison of grade inflation by private and public secondary schools in Portugal

Fairness in access to HE is unarguably a subject of paramount importance. Wherever a student’s secondary school scores are relevant for access to HE, grade inflation practices may jeopardize fair access. Pressures for high grading are common in the context of educational consumerism and competition between schools and students. However, they are not equally distributed across different types of schools, given that they have distinct relationships with the State and the market, and work with distinct populations. Specifically, the schools that are more subject to market pressures (namely private schools) are, in principle at least, the ones with more incentives to inflate their students’ grades. This paper presents an empirical study based on a large, 11 years database on scores in upper secondary education in Portugal, probing for systematic differences in grade inflation practices by four types of schools: public schools, government-dependent private schools, independent (fee-paying) private schools, and specially funded public schools in disadvantaged areas (TEIP schools). More than 3 million valid cases were analysed. Our results clearly show that independent private schools inflate their students’ scores when compared to the other types of schools. They also show that this discrepancy is higher where scores matter most in competition for HE access. This means that—usually wealthier—students from private independent schools benefit from an unfair advantage in the competition for the scarce places available in public higher education. We conclude discussing possible solutions to deal with such an important issue.     

De Genève à Belo Horizonte,une histoire croisée: circulation,réception et réinterprétation d’un modèle européen des classes spéciales au Brésil des années 1930

L’organisation des classes homogènes selon le niveau de développement mental des élèves et celle des classes spéciales pour les enfants en retard scolaire eut lieu dans les écoles élémentaires de Belo Horizonte, au Brésil, pendant les années de 1930, dans le cadre d’une réforme du système d’éducation, à laquelle participèrent des spécialistes étrangers, et en spécial la psychologue russe Helena Antipoff (1892–1974). Le projet des classes spéciales alors établies et leurs transformations dans le contexte brésilien sont étudiés à partir de données documentaires publiées entre 1930 et 1940. Née en Russie, Antipoff a fait des études supérieures en France (1910–1911), comme stagiaire dans le laboratoire Binet-Simon, et à Genève (1912–1914), à l’Institut Jean-Jacques Rousseau, où elle exerça ultérieurement les fonctions d’assistante d’Édouard Claparède (1926–1929). Notre hypothèse est que les classes spéciales créées à Belo Horizonte le furent sur le modèle genevois, et constituèrent un important exemple de circulation et diffusion de connaissances au niveau international, ainsi que de construction de repères dans le domaine de l’éducation spéciale au Brésil. Ainsi, la division des classes par niveau intellectuel mesuré par des tests d’intelligence, l’idée de “l’école sur mesure” proposée par Claparède, le dialogue avec les méthodes suggérées par Alice Descouedres démontrent les relations avec le modèle genevois. En même temps, l’interprétation des résultats des tests comme manifestation d’une forme d’ “intelligence civilisée” et les adaptations des exercices d’orthopédie mentale pour développer cette intelligence demandée par l’école montrent les transformations du modèle dans le contexte brésilien.