Identifying profiles of children at risk of being less physically active: an exploratory study using a self-organised map approach for motor competence

This study aims to develop profiles in children according to physical fitness, actual and perceived motor competence, and to examine the level of engagement in physical activity and weight status according to these profiles. In the study, 156 typically developing Spanish children (47.4% girls) of primary school age (5–11 years-old) participated voluntarily. Children’s perceived and actual motor competence, physical fitness, physical activity participation and weight status were assessed. A Self-Organising Map and K-means cluster analysis were used to classify and visualise the values. Four profiles were found: profile 2 was aligned – high capacity, high perception, profile 1 was partially aligned – medium capacity and perception, profile 3 and 4 were both non-aligned – low capacity, medium perception and medium capacity, low perception; respectively. Children in profile 2 were more active than children in profile 3 and 4 (P < .05). In profile 2 there was a lower frequency of overweight/obese children than normal-weight children. On the contrary, in profiles 1, 3 and 4 a similar distribution of normal-weight and overweight/obese children was found. High capable children with high perception exhibited higher physical activity participation and were more likely to be of normal-weight compared to those with low capacity and/or perception.     

隔网对抗项目运动技能学习的前馈控制研究

对研究所涉及到基本问题隔网对抗项目、运动技能、前馈控制进行定义描述。为研究方便将隔网对抗项目运动技能分成"选位"、"移动"、"击球"、"过渡"四个环节,并从结构、功能等方面介绍了各个阶段的动作要领。结合前馈控制原理,分别指出各个阶段练习时所需要的重点强化内容,有效学习方法选用的原则,并从知识学习过程上论证了领会学习法的优势。     

Differences in associations of product- and process-oriented motor competence assessments with physical activity in children

ABSTRACT

There is a positive association between motor competence and physical activity in child populations. Little is known about the relative variance explained in physical activity when process- versus product-oriented approaches are used for evaluating motor competence. This study aimed to examine associations between product- and process-oriented motor competence assessments and their capability to explain variance in physical activity. Participants included 167 children between the ages of 6–9 years. The run, jump, throw and kick were assessed using process-oriented (Test of Gross Motor Development-2^nd edition) and product-oriented (run time, jump distance, throw and kick speed) assessments. Physical activity was assessed via Yamax Digi-walker NL2000 pedometers. Weak to strong correlations between process and product assessments were found (range: r = ± 0.01 to ±0.81). Statistically significant correlations between process and product scores were more frequent for the kick and throw. Both product- and process-oriented assessments were poor at explaining variance in pedometer assessed physical activity. No more than 4% of variance in physical activity could be explained by a single skill, regardless of whether product or process scores were used. Continued examination of associations between process- and product-oriented assessments may provide a more holistic understanding of motor competence across developmental time.     

龙门刨床工作台电气传动系统的改造

本文阐述了运用西门子6RA70全数字直流调速系统和三菱FX2N-80MR型PLC对龙门刨床工作台电气传动系统进行改造,对6RA70全数字直流调速系统的调试运行作详细介绍。     

基于虚拟仪器的电机转速检测系统

基于美国NI公司的LabVIEW图形化编程语言,针对电机参数的检测进行虚拟仪器编程设计,开发出电动机转速和机电时间常数的在线测试系统.该系统分为人机界面,功能模块和外部电路三部分,改进了传统仪器在显示、储存、读取方面的限制.     

Passive control of Permanent Magnet Synchronous Motor chaotic system based on state observer

INTRODUCTION Many people paid attention to passive theory and used it to control chaotic dynamical systems (Byrnes and Isidori, 1991; Yu, 1999). Yu (1999) studied the passive equivalence of the Lorenz chaotic system and presented the method of passive control of chaotic system. Using passive theory, Qi and Zhao (2005) researched on the control of Permanent Magnet Synchronous Motor chaotic system, and stabilized the system at different equilibrium points. However, in order to design th…     

Prognostic relevance of motor talent predictors in early adolescence: A group- and individual-based evaluation considering different levels of achievement in youth football

ABSTRACT

In the debate about the usefulness of motor diagnostics in the talent identification process, the prognostic validity for tests conducted in early adolescence is of critical interest. Using a group- and individual-based statistical approach, this prospective cohort study evaluated a nationwide assessment of speed abilities and technical skills regarding its relevance for future achievement levels. The sample consisted of 22,843 U12-players belonging to the top 4% in German football. The U12-results in five tests served as predictors for players’ selection levels in U16-U19 (youth national team, regional association, youth academy, not selected). Group-mean differences proved the prognostic relevance for all predictors. Low individual selection probabilities demonstrated limited predictive values, while excellent test results proved their particular prognostic relevance. Players scoring percentile ranks (PRs) ≥ 99 had a 12 times higher chance to become youth national team players than players scoring PR < 99. Simulating increasing score cut-off values not only enhanced specificity (correctly identified non-talents) but also led to lower sensitivity (loss of talents). Extending the current research, these different approaches revealed the ambiguity of the diagnostics’ prognostic relevance, representing both the usefulness and several pitfalls of nationwide diagnostics. Therefore, the present diagnostics can support but not substitute for coaches’ subjective decisions for talent identification, and multidisciplinary designs are required.     

Self-controlled learning benefits: exploring contributions of self-efficacy and intrinsic motivation via path analysis

Research has shown learning advantages for self-controlled practice contexts relative to yoked (i.e., experimenter-imposed) contexts; yet, explanations for this phenomenon remain relatively untested. We examined, via path analysis, whether self-efficacy and intrinsic motivation are important constructs for explaining self-controlled learning benefits. The path model was created using theory-based and empirically supported relationships to examine causal links between these psychological constructs and physical performance. We hypothesised that self-efficacy and intrinsic motivation would have greater predictive power for learning under self-controlled compared to yoked conditions. Participants learned double-mini trampoline progressions, and measures of physical performance, self-efficacy and intrinsic motivation were collected over two practice days and a delayed retention day. The self-controlled group (M = 2.04, SD = .98) completed significantly more skill progressions in retention than their yoked counterparts (M = 1.3, SD = .65). The path model displayed adequate fit, and similar significant path coefficients were found for both groups wherein each variable was predominantly predicted by its preceding time point (e.g., self-efficacy time 1 predicts self-efficacy time 2). Interestingly, the model was not moderated by group; thus, failing to support the hypothesis that self-efficacy and intrinsic motivation have greater predictive power for learning under self-controlled relative to yoked conditions.     

电机及电力拖动实验教学方式改革探索

针对实验教学目标的能力定位,对电机及电力拖动实验教学方式进行了改革,突出了实验技能和工程问题分析能力的培养。     

Age and sex differences in motor performance of pre‐school Nigerian children

Differences in motor performance according to chronological age and gender of 341 young Nigerian children (ages 3 to 5) were examined. Motor test items designed by Morris et al. (1981) were administered to the subjects. Analysis of variance was used to determine significant differences in the motor performance of the groups. In the whole sample, more age differences than sex differences in performance were noted. Except for the balancing and running performances of the girls, a fairly linear trend of improvement with age was observed in the motor performances of the groups. At each age level the boys consistently performed better than the girls in four of the six motor tests (catching, standing long jump, tennis ball throw and speed run). Generally, the 4‐ and 5‐year‐old children performed homogeneously, with a great disparity in performance noted for the 3‐year‐old children. The results of this study confirm that age and sex differences in motor performance occur at early childhood. Prospective studies should seek to control the extraneous factors which influence motor development and account for the observed differences in motor performance of pre‐school children.