The kinematic differences between off-spin and leg-spin bowling in cricket     

Aaron J. Beach  René E. D. Ferdinands  Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(3):295-313

Spin bowling is generally coached using a standard technical framework, but this practice has not been based upon a comparative biomechanical analysis of leg-spin and off-spin bowling. This study analysed the three-dimensional (3D) kinematics of 23 off-spin and 20 leg-spin bowlers using a Cortex motion analysis system to identify how aspects of the respective techniques differed. A multivariate ANOVA found that certain data tended to validate some of the stated differences in the coaching literature. Off-spin bowlers had a significantly shorter stride length (p = 0.006) and spin rate (p = 0.001), but a greater release height than leg-spinners (p = 0.007). In addition, a number of other kinematic differences were identified that were not previously documented in coaching literature. These included a larger rear knee flexion (p = 0.007), faster approach speed (p < 0.001), and flexing elbow action during the arm acceleration compared with an extension action used by most of the off-spin bowlers. Off-spin and leg-spin bowlers also deviated from the standard coaching model for the shoulder alignment, front knee angle at release, and forearm mechanics. This study suggests that off-spin and leg-spin are distinct bowling techniques, supporting the development of two different coaching models in spin bowling.  相似文献   

Exploring the everyday realities of grass-roots football coaching: towards a relational perspective     

Paul Potrac  Lee Nelson  Jimmy O’Gorman 《Soccer & Society》2016,17(6):910-925

While scholars have increasingly engaged with the (micro)political and emotional experiences of coaches in professional and semi-professional football, little attention has been given to grass-roots coaches’ understandings of these issues. The aim of this paper is to outline one possible research agenda that could contribute to the development of a rich and increasingly nuanced understanding of the everyday realities of being a grass-roots football coach. In particular, we consider (volunteer) coaches’ participation in grass-roots football to be an inherently relational endeavour. Following the presentation of a creative fiction that is based upon our shared experiences of being grass-roots football coaches, we then illustrate how relational thinking might be productively applied to exploring the social, (micro)political and emotional features of grass-roots football coaching.  相似文献   

Effect of repeat-sprint training in hypoxia on post-exercise interleukin-6 and F2-isoprostanes     

Paul S. R. Goods  Brian Dawson  Grant J. Landers  Christopher J. Gore  Kevin Croft  Peter Peeling 《European Journal of Sport Science》2016,16(8):1047-1054

This investigation examined the oxidative stress (F₂-Isoprostane; F₂-IsoP) and inflammatory (interleukin-6; IL-6) responses to repeat-sprint training in hypoxia (RSH). Ten trained male team sport athletes performed 3(sets)*9(repetitions)*5?s cycling sprints in simulated altitude (3000?m) and sea-level conditions. Mean and peak sprint power output (MPO and PPO) were recorded, and blood samples were collected pre-exercise, and again at 8 and 60?min post-exercise. Both MPO and PPO were significantly reduced in hypoxia (compared to sea-level) in the second (MPO: 855?±?89 vs. 739?±?95?W, p?=?.006; PPO: 1024?±?114 vs. 895?±?112?W, p?=?.010) and third (MPO: 819?±?105 vs. 686?±?83?W, p?=?.008; PPO: 985?±?125 vs. 834?±?99?W, p?=?.008) sets, respectively. IL-6 was significantly increased from pre- to 1?h post-exercise in both hypoxia (0.7?±?0.2 vs. 2.4?±?1.4?pg/mL, p?=?.004) and sea-level conditions (0.7?±?0.2 vs. 1.6?±?0.3?pg/mL, p?d?=?0.80) suggesting higher IL-6 levels of post-hypoxia. F₂-IsoP was significantly lower 1?h post-exercise in both the hypoxic (p?=?.005) and sea-level (p?=?.002) conditions, with no differences between trials. While hypoxia can impact on exercise intensity and may result in greater post-exercise inflammation, it appears to have little effect on oxidative stress. These results indicate that team sport organisations with ready access to hypoxic training facilities could confidently administer RSH without significantly increasing the post-exercise inflammatory or oxidative stress response.  相似文献   

Measurement precision of body composition variables in elite wheelchair athletes,using dual-energy X-ray absorptiometry     

Mhairi Keil  Julia O. Totosy de Zepetnek  Katherine Brooke-Wavell 《European Journal of Sport Science》2016,16(1):65-71

The purpose of this study was to assess the reproducibility of body composition measurements by dual-energy X-ray absorptiometry (DXA) in 12 elite male wheelchair basketball players (age 31 ± 7 years, BMI 21 ± 2 kg/m² and onset of disability 25 ± 9 years). Two whole body scans were performed on each participant in the supine position on the same day, using Lunar Prodigy Advance DXA (GE Lunar, Madison, WI, USA). Participants dismounted from the scanning table and were repositioned in-between the first and second scan. Whole body coefficient of variation (CV) values for bone mineral content (BMC), fat mass (FM) and soft tissue lean mass (LTM) were all <2.0%. With the exclusion of arm FM (CV = 7.8%), CV values ranged from 0.1 to 3.7% for all total body and segmental measurements of BMC, FM and LTM. The least significant change that can be attributed to the effect of treatment intervention in an individual is 1.0 kg, 1.1 kg, 0.12 kg for FM, LTM, and BMC, respectively. This information can be used to determine meaningful changes in body composition when assessed using the same methods longitudinally. Whilst there may be challenges in the correct positioning of an individual with disability that can introduce greater measurement error, DXA is a highly reproducible technique in the estimation of total and regional body composition of elite wheelchair basketball athletes.  相似文献   

Effects of load mass carried in a backpack upon respiratory muscle fatigue     

Mark Faghy  Sam Blacker  Peter I. Brown 《European Journal of Sport Science》2016,16(8):1032-1038

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20?kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60?min walking at 6.5?km?h^?1 wearing a backpack of either 0 (LC₀), 10 (LC₁₀), 15 (LC₁₅) or 20?kg (LC₂₀). Inspiratory (P_Imax) and expiratory (P_Emax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60?s of each trial. Results: Group mean P_Imax and P_Emax were unchanged following 60-min load carriage in all conditions (p?>?.05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p?p?>?.05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20?kg in a backpack for up to 60?min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.  相似文献   

Education and social cohesion: developing a framework for education sector reform in Sri Lanka1     

Peter Colenso 《Compare》2005,35(4):411-428

There is increasing interest in understanding and describing the links between education and ‘social cohesion’. However, the theoretical and empirical base for understanding these links is limited. There is also a shortage of practical tools for education policy‐makers and planners, to help them assess the impact of policies and investments, and to plan for future reform. This paper describes the initial development of an analytical and planning framework for addressing education and social cohesion within the context of a sector‐wide approach to education reform in Sri Lanka. A brief literature review suggests three inter‐connected domains in which links between education and social cohesion might be usefully analysed, together with three working hypotheses: (i) political economy/governance: education affects social cohesion through transparency and participation in education policy formulation, planning and management; (ii) equity/equality of opportunity: education affects social cohesion through the distribution of education resources, opportunities and outcomes; (iii) teaching/learning: education affects social cohesion through the development of certain competencies in students. Drawing on this analytical framework, research conducted in Sri Lanka is used to identify a set of interventions to promote social cohesion, with corresponding baseline, process and outcome indicators as benchmarks for measuring the progress and impact of intended policy measures. This process is described within the context of a ‘sector‐wide approach’ to education reform, intended to bring together the activities of the government and external partners within a single comprehensive medium‐term planning and budgetary framework.  相似文献   

The Nature–Nurture Question: Teachers’ perceptions of how genes and the environment influence educationally relevant behaviour     

Sheila O. Walker  Robert Plomin 《教育心理学》2005,25(5):509-516

Despite a substantial body of research suggesting genetic influence on educationally relevant behavioural traits, it is not clear how the nature–nurture question is perceived by teachers. In order to answer this question, we surveyed 667 UK primary school teachers, and for comparison also surveyed 1,340 parents about their perceptions of genetic and environmental influence on personality, intelligence, behaviour problems, learning difficulties, and mental illness. For these five domains of behaviour, the percentages of teachers who reported that genetics were at least as important as environment were .87, .94, .43, .94, and .91, respectively. Results for parents were similar (.92, .93, .54, .86, and .89). We also found that 80% of teachers reported no coverage of genetics during teacher training.  相似文献   

Knowledge acquisition by computerized audiovisual feedback     

Fischer  Peter Michael  Mandl  Heinz 《European Journal of Psychology of Education - EJPE》1988,3(2):217-233

The present article gives an outline of the state of art in computer assisted intervention by learning-concomitant differential feedback. Based on the spectrum of possible meanings and interpretations given to the concepts ‘interaction’ and ‘interactive’ this concept is elaborated and illustrated by prototypical theoretical approaches. Based on our own empirical findings arguments are given showing that sophisticated audiovisual interactive new technologies can properly be used even on the small machines available in schools if the content materials and the flow of control given to the learner are carefully designed and based on principles of cognitive science.

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The study of butterflies     

Peter Smetacek 《Resonance》2001,6(5):8-15

In this part of the series on butterflies, we look at the types of variations found within species as well as their causes.  相似文献   

Comment: Reasoning with conditionals     

Peter F. W. Preece 《科学教学研究杂志》1993,30(9):1209-1210

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