Realistic evaluation of hull performance for rowing shells, canoes, and kayaks in unsteady flow

In this study, we investigated the effect of hull dynamics in shallow water on the hydrodynamic performance of rowing shells as well as canoes and kayaks. An approach was developed to generate data in a towing tank using a test rig capable of reproducing realistic speed profiles. The impact of unsteady shallow-water effects on wave-making resistance was examined via experimental measurements on a benchmark hull. The data generated were used to explore the validity of a computational approach developed to predict unsteady shallow-water wave resistance. Comparison of measured and predicted results showed that the computational approach correctly predicted complex unsteady wave-resistance phenomena at low oscillation frequency and speed, but that total resistance was substantially under-predicted at moderate oscillation frequency and speed. It was postulated that this discrepancy arose from unsteady viscous effects. This was investigated via hot-film measurements for a full-scale single scull in unsteady flow in both towing-tank and field-trial conditions. Results suggested a strong link between acceleration and turbulence and demonstrated that the measured real-world viscous-flow behaviour could be successfully reproduced in the tank. Thus a suitable tank-test approach could provide a reliable guide to hull performance characterization in unsteady flow.     

高职大学生体质下降因子分析对策

采用文献资料法、测量法、数理统计法;以宁波市高职在校的大二学生实施《学生体质健康标准》测试的数据为依据,进行统计分析研究.针对影响学生体质的身体形态因子、机能因子、素质因子针对性的提出对策.以求为改善、增强高职院校学生健康为目标的体育教学体系和课程改革提供可参考的依据.     

Latent growth curve modeling in exercise science

ABSTRACT

Longitudinal measurement enables the examination of behavioral or psychological change. One approach to examining longitudinal measurements is the use of latent growth curve modeling (LGCM). This approach affords the assessment of inter- and intraindividual change. Yet, this approach likely is underused in exercise science. The purpose of the current study was to describe and demonstrate the use of LGCM to examine change using multiple measurements in the field of exercise science. We first provide a substantive review of LGCM. We highlight the use of unconditional models to find an appropriate model of change, how and why to utilize autoregressions, and how to examine predictors of change in conditional models. We then provide an illustration of the approach using data from the Michigan State Motor Performance Study. In the conclusion, we discuss the advantages and limitations of the approach and suggest future directions when assessing longitudinal data in exercise science.     

Methode zur Aktivenraten-Prognose in der Sportentwicklungsplanung

The quantitative sports development planning needed as a basis a forecast of sports practice on the quantitative extent and location. To support this it would be helpful to have cohort data, but their preparation needed at least a generation time, but then they would already be out of date. It is therefore appropriate to go back to resorted longitudinal data in lower age subdivisions which are, in a suitable manner with modified cross-sectional data are linked. Which is common practice, for example in the preparation of forecasting mortality tables for demographic prognosis. In the previous practice were predominantly empirical data on sport activity are kept constant and only linked to the future population. The survey results have only been published for age classes, which is unsuitable for a prognosis. The paper shows alternative how such class values in single year of age data can be transmitted when the results of an empirical study have been published only grouped. Then we made a suggestion as to how the development of cohorts in longitudinal section and the age specific sports activity can be linked to a forecast. For this, the sports activity is expressed as active rate (physically active inhabitants/1000 residents) defined and consistently over all ages from 0 to 99 years and more developed. From this it can be a measure of the active sporting years under the conditions of study year developed. These are the combined active rates, as can be expressed as years active in sports per inhabitant, when the ratios of the survey year would apply to the entire population. The new code is similar to the “combined birth rate” in the demography, where they give good services in analysis and forecasting. The forecast latitude per year of age is limited by external circumstances, so that it never reached 1000 active per 1000 inhabitants. These are the “obstacle rates” to determine inhabitants who are hindered to active sports at that age in that year. As the difference between the unattainable maximum of 1000 minus the obstacle rate to the current active rate results in the age specific prognosis latitude, called “potential rate”. From present periodic surveys of the extent of sporting engagements by age and sex and its projection on the entire forecast period results in “years with sport” expressible annual change. Oriented to the also changing annual potential rates may apply to the change volume sports years are divided annually to the individual age years. This is a data forecast oriented on longitudinal and cross-sectional data of the degree of physical activity in the form of an age-specific active rate.     

Considerations for the use of functional principal components analysis in sports biomechanics: examples from on-water rowing

The proliferation of new biomechanical technology in laboratory and field settings facilitates the capture of data-sets consisting of complex time-series. An understanding of the appropriate statistical approaches for analysing and interpreting these data-sets is required and the functional data analysis (FDA) family of statistical techniques has emerged in the biomechanical literature. Given the use of FDA is currently in its infancy with biomechanical data, this paper will form the first of a two part series aiming to address practical issues surrounding the application of FDA techniques in biomechanics. This work focuses on functional principal components analysis (fPCA), which is explored using existing literature and sample data from an on-water rowing database. In particular methodological considerations for the implementation of fPCA such as temporal normalisation of data, removal of unwanted forms of variation in a data-set and documented methods for preserving the original temporal properties within a set of curves are explored in detail as a part of this review. Limitations and strengths of the technique are outlined and recommendations are provided to encourage the appropriate use of fPCA within the field of applied sports biomechanics.     

安徽省大学生1985～2000年体质状况动态分析研究

根据安徽省大学生体质调研数据 ,应用文献资料调研、体质测试、逻辑分析等研究方法 ,对我省 19～ 2 2岁大学生的体质健康状况进行了横向和纵向的系统分析研究 ,揭示了其形态发育和生理机能发育水平以及身体素质发展水平的规律变化 ,为我省主管部门的决策提供基础资料和科学依据     

A shot taxonomy in the era of tracking data in professional tennis

Shots are an essential part of the language of tennis yet little is known about the distinct types of shots in the professional game. In this study, we build a taxonomy of shots for elite tennis players using tracking data from multiple years of men’s and women’s matches at the Australian Open. Our taxonomy is constructed using model-based multi-stage functional data clustering, an unsupervised machine learning approach. Among 270,023 men’s and 178,136 women’s shots, we found 13 distinct types of serves to both the Ad and Deuce court for male players and 17 and 15 types to the Ad and Deuce for female players. More variety was found among serve returns and rally shots compared to the serve; with less variety on the backhand than forehand. There was also more overlap in the physical characteristics of groundstroke shots between male and female players than on serve. Shot type was strongly associated with winning points and shots in the highest speed and lowest net clearance categories tended to be the most effective. This data-driven dictionary of shots provides a framework for analysis of elite player performance, characterizing playing style, and designing more representative practice.     

The scientific foundations and associated injury risks of early soccer specialisation

ABSTRACT

Early specialisation is characterised by formal participation in a single sport at the exclusion of others. Limited data are available to support this approach in the development of soccer players who attain elite status later in life. Of growing concern is the associated increased risk of injury and suggestions that single sport specialisation is a risk factor independent of age, growth, biological maturation and training volumes. In the United Kingdom, elite soccer organisations have recently adopted an early sport specialisation approach following the introduction of the Elite Player Performance Plan. A key tenet of this programme is increased opportunities for training through a marked rise in the specified on-pitch hours per week. The accumulation of high training hours may be less of a relevant marker for success, and the impact of such a significant increase in training volume for young athletes who are experiencing a range of growth and maturational processes is currently unknown. This critical commentary includes an evidence-based discussion of the effectiveness of early sport specialisation and the potential injury risks associated with such programmes placing a specific focus on elite male youth soccer players. Available data indicate that modifications to the existing Elite Player Performance Plan framework could enhance players’ development and reduce injury risk. Proposed alterations include reduced volume of soccer-specific training at key stages of growth and maturation and guidelines for the provision of a greater variety of physical activities that are integrated within other programme components.     

Endurance tests are the most reliable core stability related measurements

PurposeTo determine the intra-tester reliability of clinical measurements that assess five components related to core stability: strength, endurance, flexibility, motor control, and function.MethodsParticipants were 15 college-aged males who had not suffered any orthopedic injury in the past year. Core strength measurements included eight isometric tests and a sit-up test. The four core endurance tests were the trunk flexor test, trunk extensor test, and bilateral side bridge tests. Flexibility tests included the sit-and-reach test and active range of the trunk and hip joint motions. Proprioception via passive reposition tests of the hips and a single limb balance test on an unsteady platform were used to evaluate core motor control. Functional measurements consisted of a squat test and a single leg hop test for time and distance. Measurements were performed during two data collection sessions with a week's rest between the sessions. Intra-class correlation coefficients were calculated to establish reliability.ResultsThe overall intra-rater reliability for all core stability related measurements ranged from low (ICC = 0.35, left hip reposition) to very high (ICC = 0.98, sit-and-reach). As a group, the core endurance tests were observed to be the most reliable.ConclusionThere are highly reliable tests in each of the five groups. Overall, core endurance tests are the most reliable measurements, followed by the flexibility, strength, neuromuscular control, and functional tests, respectively.     

Childhood single skinfold thickness is a better predictor for adult relative fat mass in females than the body mass index: Data from a 30-year longitudinal growth study

Abstract

Information on the prediction of adult relative fat mass (percent body fat,%BF) using measures from pre-pubertal ages and early childhood is scarce. In the present longitudinal study, we assess the development of different anthropometric indicators of percent body fat during childhood, adolescence, and adulthood in 37½-year-old females stratified for low and high percent body fat. Consequently, we study the predictability of percent body fat based on simple anthropometric measurements during childhood and adolescence.

Anthropometric data from the Belgian longitudinal experimental growth study “LEGS” were used. Beginning in 1969, five yearly cohorts of about 100 individuals each (mean age 6 years) were recruited in public kindergartens. Of the original 515 participants (260 males, 255 females) that were measured annually from age 6 to 18 years, 59 males and 60 females agreed to participate in a follow-up study in 2004. During the follow-up measurements, the participants were invited for a body-composition assessment by bioelectrical impedance analysis (BIA). We stratified the participants into low (%BF-BIA < 35%) and high (%BF-BIA≥35%) relative fat mass samples. Pearson correlations were calculated and used as tracking coefficients. Multiple stepwise linear regression was applied with anthropometric variables at each age separately as predictors for adult percent body fat, expressed as%BF-BIA, %BF-Segal, and %BF-D&W (Durnin & Womersley, 1974).

The results indicate that a single skinfold thickness during adolescence is a better predictor for adult percent body fat than adolescent body mass index. Additionally, our results suggest that this holds during childhood as early as from age 8 onwards. The use of single skinfold measurements as predictors for adult adiposity and obesity is supported by other arguments, including: (1) body mass index as a proxy for overweight does not discriminate between fat mass and fat-free mass, and (2) an excess of adipose tissue is more strongly associated with morbidity than the body mass index.     

Leveraging community sport organizations to promote community capacity: Strategic outcomes,challenges, and theoretical considerations

Community sport organizations (CSOs) provide valuable contexts for promoting community development. These initiatives are most effective when they involve local stakeholders in the process of development. A key first step to achieving this objective is building community capacity, defined as local stakeholders’ skills, knowledge, and resources that may be leveraged for change. Interestingly, despite this conceptual importance, few researchers have focused on capacity building in the sport context. This has limited the theoretical advancement of community capacity theory as it relates to CSOs and community development. Using a qualitative case study approach, the authors analyze the outcomes and challenges of implementing community capacity building strategies in an American CSO, and draw on the empirical data to contribute to this theoretical conversation. Interviews, participant observation, and document analysis were used to generate data, and deductive techniques were used for thematic analysis. The results highlight the outcomes of the capacity building strategies and challenges associated with implementation. In addition, the conclusion focuses on theoretical contributions to community capacity theory, namely the role of sport in facilitating inter-community relations across social groups and the link with process models of organizational capacity.     

A generalized rank-order method for nonparametric analysis of data from exercise science: a tutorial

Frequent violations of the assumption that data are normally distributed occur in exercise science and other life and behavioral sciences. When this assumption is violated, parametric statistical analyses may be inappropriate for data analysis. We provide a rationale for using a generalized form of nonparametric analyses based on the Puri and Sen (1985) L treated as a chi 2 approximation. If data do not meet the assumption of normality, this nonparametric approach has substantial power and is easy to use. An advantage of this generalized technique is that ranked data may be used in standard parametric statistical programs widely available on desktop and mainframe computers, for example, regression, analysis of variance (ANOVA), multivariate analysis of variance (MANOVA) within BioMed, SAS, SPSS. Once the data are ranked and analyzed with these programs, the only adjustment required is to use a standard formula to calculate the nonparametric test statistic, L, instead of the parametric test statistic (e.g., F). Thus, rank-order nonparametric models become parallel with their parametric counterparts allowing the researcher to select between them based on characteristics of the data distribution. Examples of this approach are provided using data from exercise science for regression, ANOVA (including repeated measures) and MANOVA techniques from SPSSPC. Using these procedures, researchers can easily examine data distributions and make an appropriate decision about parametric or nonparametric analyses while continuing to use their regular statistical packages.     

Model-based automatic tracking of articulated human movement

This study applied a vision-based tracking approach to the analysis of articulated, three-dimensional (3D) whole-body human movements. A 3D computer graphics model of the human body was constructed from ellipsoid solids and customized to two gymnasts for size and colour. The model was used in the generation of model images from multiple camera views with simulated environments based on measurements taken on each of three synchronized video cameras and the lighting sources present in the original recording environment. A hierarchical procedure was used whereby the torso was tracked initially to establish whole-body position and orientation and subsequently body segments were added successively to the model to establish body configuration. An iterative procedure was used at each stage to optimize each new set of variables using a score based on the RGB colour difference between the model images and video images at each stage. Tracking experiments were carried out on movement sequences using both synthetic and video image data. Promising qualitative results were obtained with consistent model matching in all sequences, including sequences involving whole-body rotational movements. Accurate tracking results were obtained for the synthetic image sequences. Automatic tracking results for the video images were also compared with kinematic estimates obtained via manual digitization and favourable comparisons were obtained. It is concluded that with further development this model-based approach using colour matching should provide the basis of a robust and accurate tracking system applicable to data collection for biomechanics studies.     

基于泛函分析的大学生体育舞蹈综合素质动态变化的量化评估模型

为了深入分析与评估大学生体育舞蹈综合素质变化情况,确立了一种用于系统化评估大学生体育舞蹈综合素质变化的整体思路,选择了评估参照信息并给出其测度方法;结合当代体育舞蹈特色确定了评估指标并给出评估指标的计算方法;随后,基于泛函分析方法建立了大学生体育舞蹈综合素质动态变化的评估模型,说明了模型的功能及使用方法,以湖南商学院为例进行评估实验验证了本文方法可行性、实用性、有效性。     

Multiple Time Scale Models in Sport and Exercise Science

In sport and exercise research, examining both within- and between-individual variation is crucial. The ability to investigate change both within competitive events and across a competitive season is a priority for many sport researchers. The aim of this article is to demonstrate an approach to analyzing intensive longitudinal data collected through time-scale-dependent longitudinal designs. Following didactic presentation of the approach, two illustrations from secondary data analysis are used to describe the modeling process in detail. Illustration 1 includes affective response data from an exercise intervention randomized pilot study. Illustration 2 uses referee and player distance data collected during professional soccer games in the English Premier League. Each illustration describes a process for testing and comparing multiple time scale models based on the three-level multilevel model, and results are interpreted. In the discussion, advantages and limitations of the approach are highlighted.     

老年人功能性健身智能监控系统的设计

本文综合运用专家访谈法、文献资料法、数理统计法等多种科研方法,针对中国人口老龄化的问题,集中解决物联网核心技术分析、功能性健身方案修订、物联网平台的数据收集及管理、功能性锻炼方法设计四大关键问题,以实用性的健身方法通过云端服务于社区老年人,旨在提升老年人群的生活基础体能锻炼的安全性,解决老年人运动常见性问题,在一定程度上减轻家庭、社会和国家的负担;加速老年人健康事业的发展,满足老年人日益增长的多元化健身需求,为国家制定老年人健康发展计划提供直接有效的应用解决方案,从而推动"全民健身"事业的发展。