Effect of hand paddles and parachute on backstroke coordination and stroke parameters

Hand paddles and parachutes have been used in order to overload swimmers, and consequently increase the propulsive force generation in swimming. However, their use may affect not only kinematical parameters (average speed, stroke length and stroke rate), but also time gaps between propulsive phases, assessed through the index of coordination (IdC). The objective of this study was to assess the effects of hand paddles and parachute use, isolated or combined, on kinematical parameters and coordination. Eleven swimmers (backstroke 50-m time: 29.16 ± 1.43 s) performed four 15-m trials in a randomised order at maximal intensity: (1) without implements (FREE), (2) with hand paddles (HPD), (3) with parachute (PCH) and (4) with hand paddles plus parachute (HPD+PCH). All trials were video-recorded (60 Hz) in order to assess average speed, stroke rate, stroke length, five stroke phases and index of coordination. When average swimming speed was compared to FREE, it was lower in PCH and HPD+PCH, and higher in HPD. Stroke rate decreased in all overloaded trials compared to FREE. The use of hand paddles and parachute increased and decreased stroke length, respectively. In addition, propulsive phase duration was increased when hand paddles were used, and time gaps shifted towards zero (no time gap), especially when hand paddles were combined with parachute. It is conceivable that the combined use of hand paddles and parachute, once allowing overloading both propulsive and resistive forces, provides a specific stimulus to improve muscle strength and propulsive continuity.     

Introducing perception and modelling of spatial randomness in classroom

A strategy to facilitate understanding of spatial randomness is described, using student activities developed in sequence: looking at spatial patterns, simulating approximate spatial randomness using a grid of equally‐likely squares, using binomial probabilities for approximations and predictions and then comparing with given Poisson probabilities. Key questions are discussed with students on concepts needed to understand the approximate models and to generate predictions based on the approximations. The sequence is structured to be interactive to encourage student's interest and curiosity.     

Explaining as Mediated Action

Explaining is one of the most important everyday practices in science education. In this article, we examine how scientific explanations could serve as cultural tools for members of a group of pre-service physics teachers. Specifically, we aim at their use of explanations about forces of inertia in non-inertial frames of reference. A basic assumption of our study is that explanatory tools (e.g., typical explanations learned) shape the ways we think and speak about the world. Drawing on the theory of mediated action, analysis illustrates three major claims on scientific explanations: (1) explaining is an act of actively responding to explanations presented by others (and not only to evidence itself); (2) the actual experience of explaining involves the enactment of power and authority; (3) resistance (not acknowledging an explanation as one’s own) might be a constitutive part of learning how to explain (hence, teachers could approach scientific explanation in a less dogmatic way). These assertions expand the possibilities of dialogue between studies of scientific explanations and the social sciences. Implications for science teaching and research in science education are presented.     

Divergent Thinking in Italian Students with and Without Reading Impairments

Several studies have explored the relationship between dyslexia and creativity, but results have been rather mixed. This study examines whether Italian dyslexic children are more creative than their peers without a reading impairment. One hundred ninety Italian children aged between 9 and 13 participated in this study, divided into two groups: Ninety five dyslexic students and ninety five peers without a reading impairment. All the participants’ creativity skills were assessed. The results indicated that dyslexic children outperformed their peers in the total score, and in the originality, elaboration, and titles sub-scores, whereas no differences were found in the fluency and flexibility sub-scores. The results are discussed in relation to the practical implications, and provide indications for supportive learning environments.     

Science Engagement and Literacy: A Retrospective Analysis for Indigenous and Non-Indigenous Students in Aotearoa New Zealand and Australia

Previous research has underlined the importance of school students’ engagement in science (including students’ attitudes, interests and self beliefs). Engagement in science is important as a correlate of scientific literacy and attainment, and as an educational outcome in its own right. Students positively engaged with science are more likely to pursue science related careers, and to support science related policies and initiatives. This retrospective, secondary analysis of PISA 2006 national data for Aotearoa New Zealand and Australia examines and compares the factors associated with science literacy and with science engagement for indigenous and non-indigenous 15 year old students. Using a four step hierarchical regression model, our secondary analyses showed consistent patterns of influence on engagement in science for both indigenous and non-indigenous students in Aotearoa and Australia. Variations in students’ interest, enjoyment, personal and general valuing, self-efficacy, and self concept in science were most strongly associated with the extent to which students engaged in science activities outside of school. In contrast, socioeconomic status, time spent on science lessons and study, and the character of science teaching experienced by students in their schools were the factors most explanatory of variations in science literacy. Yet, the factors that explained variation in science literacy had only quite weak associations with the suite of variables comprising engagement in science. We discuss the implications of these findings for science educators and researchers interested in enhancing students’ engagement with science, and committed to contributing positively to closing the persistent gap in educational outcomes between indigenous and non-indigenous peoples.     

Is season of birth related to developmental dyslexia?

Different moderators/mediators of risk are involved in developmental dyslexia (DD), but data are inconsistent. We explored the prevalence of season of birth and its association with gender and age of school entry in an Italian sample of dyslexic children compared to an Italian normal control group. The clinical sample included 498 children (345 boys, mean age 10.3 ± 2.1 years) with DD, the control sample 1,276 children (658 boys, mean age 10.8 ± 2.2 years) from four elementary schools from the same urban area, and with the same socio-economic status level. A prevalence of birth in autumn was found among children with DD compared to controls (34% versus 24%, p < 0.0001). Children with DD were more frequently males (p < 0.0001) and had a lower mean age of school entry (p < 0.0001). Regarding the distribution of ages, 11.4% of children with DD, but none of the subjects in the control group, started school before 5.7 years. Therefore, greater risk of DD was related to age of school entry (OR = 2.72), gender (OR = 2.16), and season of birth (OR = 1.21). Significant interactions between boys with DD born in autumn, and correct school of entry (OR = 2.56) were joint predictors of higher risk of DD. The association between birth in autumn and DD may be explained by the earlier age of school entry, which may be a critical element in the youngest children with DD or at risk to DD. Whether Italian school policy is oriented to anticipate the school entry, a closer detection of early learning disorders and associated risk factors (familial load, specific language disorders, and attention deficit hyperactivity disorder) should be warranted.     

Output-feedback binary adaptive control of MIMO systems using monitoring function

The problem of adaptive control design for multivariable linear time-invariant plants with unknown control direction is considered. A solution is proposed based on the SDU factorization of the high frequency gain matrix (HFG) and the monitoring function approach. The adaptation scheme is the binary model reference adaptive control (BMRAC) which utilizes parameter projection and sufficiently high adaptation gains. The signs of the leading principal minors of the HFG define the control directions, and the lack of knowledge of which is a major challenge in the multivariable framework. The role of the monitoring function is to monitor the output error transient and then provide the necessary changes of the adaptation gain signs to guarantee a stable adaptive control. In addition to proving the signal boundedness of the resulting closed-loop system, the output tracking error is shown to be asymptotically as well as exponentially practically stable, i.e., exponentially stable with respect to a small residual compact set of size inversely proportional to the BMRAC adaptation gain. The latter implies good transient properties of the output tracking error in contrast to conventional adaptive laws which only guarantee asymptotic stability but can lead to extremely slow error convergence. The extension of the proposed approach to matched disturbances is also briefly discussed following the classical paradigm of disturbance estimators. Numerical results with a visual servoing application illustrate the efficiency of the proposed method.     

Capoeira – a Brazilian Immaterial Heritage: Safeguarding Plans and Their Effectiveness as Public Policies

This paper aims to analyse the actions promoted by the Brazilian federal government for the promotion of Capoeira, which is a mix of dance, fight and play, practised with musical instruments. It is commonly called an Afro-Brazilian martial art. So, in this paper, we analyse the effectiveness of the proposed Safeguarding Plan to Capoeira, assuming the suggested orientations from the National Historic and Artistic Heritage Institute concerning its elaboration and execution. The elaboration of safeguarding plans aims to define and organise a group of actions willing to enhance social/environmental production, as well as reproduction and transmission conditions of the registered cultural immaterial heritage. It is important to mention that Capoeira is also much related to representations about Brazil.     

The effects of vibration on explosive and reactive strength when applying individualized vibration frequencies

Abstract

The aim of this study was to assess the effects of 8 weeks of whole-body vibrations on explosive and reactive leg strength. Thirty-three physically active students took part in the study and were randomly assigned to an individualized-vibration group, a fixed-vibration group or a control group. The frequency of vibration was set to 30 Hz for the fixed-vibration group, whereas the frequency for the individualized-vibration group was determined by monitoring the participants' EMG_rms activity. The participants in the two vibration groups were exposed three times a week for 8 weeks to a series of 10 × 1-min whole-body vibrations with a 1-min pause between series of vibrations and a 4-min pause after the first five series of vibrations. Jump height in the squat jump increased significantly in all three groups (by 11% for the individualized-vibration group, p = 0.001; by 3% for the fixed-vibration group, p = 0.011; and by 2% for the control group, p = 0.006), but countermovement jump height was not affected. In continuous rebound jumps by the individualized-vibration group, jumping height increased by 22% (p = 0.006) and power increased by 18% (p = 0.002). The results of this study suggest that the use of an individualized vibration frequency produces a greater response from the neuromuscular system and is more beneficial than vibrations at a fixed pre-selected frequency.