The effects of surface traction characteristics on frictional demand and kinematics in tennis

The interaction between footwear and surfaces influences the forces experienced by tennis players. The purpose of this study was to investigate traction demand and kinematic adaptation during tennis-specific movements with changes in traction characteristics of surfaces. We hypothesised that players would increase the utilised coefficient of friction (horizontal to vertical ground reaction force ratio) when the shoe surface combination had a high coefficient of friction and flex their knee after contact to facilitate braking. Eight participants performed two separate movements, side jump out of stance and running forehand. Ground reaction force was measured and three-dimensional kinematic data were recorded. Clay surface and cushioned acrylic hard court (low vs. high shoe–surface friction) were used. The peak utilised coefficient of friction was greater on clay than the hard court. The knee was less flexed at impact on clay ( ? 5.6 ± 10.2°) and at peak flexion ( ? 13.1 ± 12.0°) during the running forehand. Our results indicate that tennis players adapt the level of utilised friction according to the characteristics of the surface, and this adaptation favours sliding on the low friction surface. Less knee flexion facilitates sliding on clay, whereas greater knee flexion contributes to braking on the hard court.     

Relationships between computational thinking and the quality of computer programs

Education and Information Technologies - Computational thinking – the ability to reformulate and solve problems in ways that can be undertaken by computers – has been heralded as a...     

Recruiting,Funding, and Hiring of Doctoral Students in Physical Education Teacher Education

ABSTRACT

This article examines trends and issues surrounding recruiting, funding, and hiring of doctoral physical education teacher education (D-PETE) students and graduates. Sources for this examination were background data collected by Boyce and her colleagues, the existing literature on these topics, and qualitative data gathered from 30 sport pedagogists during one round-table session at the National Association for Kinesiology in Higher Education (NAKHE) conference in January 2015. All three sources indicated the importance of recruiting and funding of students and hiring of graduates to the future of D-PETE programs. A number of paths were identified which sport pedagogists could follow in order to keep D-PETE programs safe and help them flourish. Unfortunately, agreement as to which of these paths the field should take was often in short supply. In the conclusions section, suggestions for future research of recruiting, funding, and hiring are made with the goal of providing data which could lead to sport pedagogists making more informed decisions regarding the future direction of D-PETE.     

Kindergarten Adjustment Difficulty: The Contribution of Children's Effortful Control and Parental Control

Research Findings: This paper examines the extent to which children's effortful control and early family experiences predict difficulty in kindergarten adjustment. One hundred and eighty-two children from 31 kindergarten classrooms in rural elementary schools in the Southeast participated. Teachers reported on children's difficulty with kindergarten adjustment, and parents completed measures assessing children's effortful control (inhibitory control and attentional focus) and types of parental control (i.e., lax, firm, and harsh). A hierarchical regression analysis was performed to address three research questions: First, how does effortful control (inhibitory control and attentional focus) contribute to children's difficulty with kindergarten adjustment? Second, how does parental control predict children's difficulty with kindergarten adjustment? Third, to what extent does parental control moderate the relation between effortful control and difficulty with kindergarten adjustment? Practice or Policy: Children lower on inhibitory control showed greater difficulty with kindergarten adjustment than children with higher inhibitory control. Furthermore, lax parental control, but not firm or harsh parental control, predicted children's adjustment problems. Lax parental control moderated the relation between children's inhibitory control and difficulty with kindergarten adjustment; specifically, higher levels of lax parental control coupled with lower levels of inhibitory control predicted more difficulty with the adjustment to kindergarten.     

Embedded Technical Expression: Code and the Leveraging of Functionality

Abstract

In this article, I argue that a key problem for understanding the social ramifications of software is an implicit separation of software programs into two separate elements: expressive aspects, which are seen as socially driven and affectual, and functional aspects, understood as scientific and rational. In order to overcome this binary, I develop an alternative framework that examines the ways software expresses best practices, correct behaviors, and social organization. A key element of this framework is an understanding of software programs as simultaneously rhetorical and tangible objects. Given that Western society is dependent on sociotechnical systems in which software plays a crucial role, understanding the complex ways software expresses normative tasks, practices, and social orders is increasingly important.     

A re-examination of the benefits of exercise for state body satisfaction: Consideration of individual difference factors

Abstract

Although the link between exercise and body image is well documented, the considerable inter-individual variability in this relationship has been largely ignored. Therefore, the aim of the present study was to test the contributions of key body image and exercise-related moderators (age, body mass index (BMI), exercise frequency, trait body dissatisfaction, internalisation of appearance standards, and body surveillance tendencies) in predicting variability in the exercise-body satisfaction relationship. Thirty-seven undergraduate women completed a questionnaire containing the above trait-based measures and then carried a Personal Digital Assistant (PDA) for a 7-day period. Participants were instructed to use the PDA to self-report their state body satisfaction immediately following an exercise session and also when the PDA signalled at each of six random intervals throughout the day. Multilevel modelling revealed a bi-directional relationship between exercise and state body satisfaction. Moreover, post-exercise increases in state body satisfaction were strongest for individuals who were younger and engaged in regular exercise, and weakest for individuals with high BMI and/or the tendency to compare their appearance with others. These findings highlight potential limits on the efficacy of exercise-based therapy for body image disturbances.     

The influence of` preseason training phase and training load on body composition and its relationship with physical qualities in professional junior rugby league players

ABSTRACT

This study investigated changes in body composition in relation to training load determined using RPE and duration (sRPE), and its relationship with physical qualities over a preseason period. Sixteen professional academy players (age = 17.2 ± 0.7 years; stature = 179.9 ± 4.9 cm; body mass = 88.5 ± 10.1 kg) participated in the study. Body composition was assessed before and after each training phase and physical qualities assessed at the start and end of preseason. Across the whole preseason period, skinfold thickness, body fat percentage and fat mass were most likely lower (ES = ?0.73 to ?1.00), and fat free mass and lean mass were likely to most likely higher (ES = 0.31 to 0.40). Results indicated that the magnitude of change appeared phase-dependent (ES = ?0.05 to ?0.85) and demonstrated large individual variability. Changes in physical qualities ranged from unclear to most likely (ES = ?0.50 to 0.64). Small to moderate correlations were observed between changes in body composition, and TL with changes in physical qualities. This study suggests training phase and TL can influence a player’s body composition; that large inter-participant variability exists; and that body composition and TL are related to the change in physical qualities.     

Conference communications

Abstract

The objective of this study was to provide anthropometric, physiological, and performance characteristics of an elite international handball team. Twenty-one elite handball players were tested and categorized according to their playing positions (goalkeepers, backs, pivots, and wings). Testing consisted of anthropometric and physiological measures of height, body mass, percentage body fat and endurance ([Vdot]O_2max), performance measures of speed (5, 10, and 30 m), strength (bench press and squat), unilateral and bilateral horizontal jumping ability, and a 5-jump horizontal test. Significant differences were found between player positions for some anthropometric characteristics (height and percentage body fat) but not for the physiological or performance characteristics. Strong correlations were noted between single leg horizontal jumping distances with 5-, 10-, and 30-m sprint times (r = 0.51–0.80; P < 0.01). The best predictors of sprint times were single leg horizontal jumping with the dominant leg and the distance measured for the 5-jump test, which when combined accounted for 72% of the common variance associated with sprint ability. In conclusion, performance abilities between positions in elite team-handball players appear to be very similar. Single leg horizontal jumping distance could be a specific standardized test for predicting sprinting ability in elite handball players.     

Science assessments for all: Integrating science simulations into balanced state science assessment systems

This article reports on the collaboration of six states to study how simulation‐based science assessments can become transformative components of multi‐level, balanced state science assessment systems. The project studied the psychometric quality, feasibility, and utility of simulation‐based science assessments designed to serve formative purposes during a unit and to provide summative evidence of end‐of‐unit proficiencies. The frameworks of evidence‐centered assessment design and model‐based learning shaped the specifications for the assessments. The simulations provided the three most common forms of accommodations in state testing programs: audio recording of text, screen magnification, and support for extended time. The SimScientists program at WestEd developed simulation‐based, curriculum‐embedded, and unit benchmark assessments for two middle school topics, Ecosystems and Force & Motion. These were field‐tested in three states. Data included student characteristics, responses to the assessments, cognitive labs, classroom observations, and teacher surveys and interviews. UCLA CRESST conducted an evaluation of the implementation. Feasibility and utility were examined in classroom observations, teacher surveys and interviews, and by the six‐state Design Panel. Technical quality data included AAAS reviews of the items' alignment with standards and quality of the science, cognitive labs, and assessment data. Student data were analyzed using multidimensional Item Response Theory (IRT) methods. IRT analyses demonstrated the high psychometric quality (reliability and validity) of the assessments and their discrimination between content knowledge and inquiry practices. Students performed better on the interactive, simulation‐based assessments than on the static, conventional items in the posttest. Importantly, gaps between performance of the general population and English language learners and students with disabilities were considerably smaller on the simulation‐based assessments than on the posttests. The Design Panel participated in development of two models for integrating science simulations into a balanced state science assessment system. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 363–393, 2012