Long-axis rotation: The missing link in proximal-to-distal segmental sequencing

Most assessments of segmental sequencing in throwing, striking or kicking have indicated a proximal-to-distal sequencing of end-point linear speeds, joint angular velocities, segment angular velocities and resultant joint moments. However, the role of long-axis rotations has not been adequately quantified and located in the proximal-to-distal sequence. The timing and importance of pronation-supination in the development of racquet head speed have been examined in the tennis serve and squash forehand drive and considered in relation to conventional concepts of proximal-to-distal sequencing. Both long-axis rotations reached their peak angular speeds late in both strokes, typically after shoulder flexion-extension, shoulder abduction-adduction and elbow extension. These results clarify and confirm the importance of upper limb long-axis rotations in the production of racquet head speed. It appears that traditional proximal-to-distal sequencing concepts are inadequate to describe accurately the complexity of the tennis serve or squash forehand drive. It is essential to consider upper arm and forearm longitudinal axis rotations in explaining the mechanics of these movements and in developing coaching emphases, strength training schedules and injury prevention programmes.     

Optimizing segmental movement in the jumping header in soccer

This study looks at segmental movements in the jumping header from an optimization viewpoint. Investigations on the header so far have focused on head restriction in the movement but have not clarified how and to what extent body segments influence the performance of the skill. In the present study a biomechanical model was used to analyze the jumping header in simulated competition to give a clear picture of an optimized header. Skilled soccer players headed balls at speeds of 13 m x s(-1) the results indicated that the head moves as a free non-restricted segment in the jumping header and should be allowed to do so, even though much soccer literature says otherwise to prevent injuries. The arm movement showed individual characteristics and gave no general advantages in optimizing ball speed after impact in the header The movement of the legs was, on the other hand, the single most important factor in the skill. Therefore, coaches and players shouldfocus on developing muscle strength in the stomach, back and pelvis and should put no restrictions on head and arm movement to optimize the jumping header.     

Promoting perseverance and challenge in physical education: the missing ingredient for improved games teaching

This paper explores critical notions about how improved understandings of students learning experiences within practical learning environments could sensitise teachers to appreciate the complex influences more that affect how levels of challenge and perseverance are constructed by students. The authors, in furthering their critique, build on the model of constructivism developed by Ollis and Sproule. This model attempted in embryonic terms to recognise the specific situational factors that most influenced the minded ways in which students identified and responded to learning challenges. In refining these ideas further the authors specifically consider how teaching games for understanding (TGfU) methodologies could be enhanced by recognising the meta-cognitions of students when constructing rich task led learning episodes. In conclusion, it is posited that comprehending the complexity of learning theory holds considerable promise for the ongoing development of physical education as a valuable and integral part of the school learning experience.     

试论篮球训练理论中的“环节论”

我国篮球训练理论在现有基础上应有新的突破,并提出“环节论”观点:(一)“环节论”的定义;(二)“环节论”体现了篮球对抗的整体规律;(三)“环节论”的核心——积极转化;(四)狠抓“两头”,关键在“转化”。     

体育报纸消息头缺失现象探析

体育消息是体育新闻的基本体式。但报纸体育新闻写作消息头缺失现象却十分严重，从某种程度上说，不仅影响了消息结构的完整性和规范性，甚至还会使人对消息来源的真实性和权威性产生疑问。从体育报纸消息头使用的必要性与缺失的危害、消息头缺失的原因探析及防止消息头缺失的建议等几个方面进行初步的探讨。     

对现代奥林匹克运动中运动员主体缺失的哲学思考

研究认为现代奥林匹克运动是随着科技的发展而不断发展,在这一过程中,科技帮助人在奥林匹克运动中彰显了自己作为主体的地位,但由于人们越来越依赖于科技,使得科技与人共同承担了运动过程与结果,造成运动员的主体地位的缺失。     

The three-dimensional kinetic behaviour of the pelvic rotation in maximal sprint running

The purpose of this study was to investigate the effect of lumbosacral kinetics on sprinting. Twelve male sprinters performed 50 m sprints at maximal effort. Kinematic and ground reaction force data were recorded at approximately 40 m from sprint commencement. A whole-body inverse dynamics approach was applied to calculate joint forces and torques at the hip and lumbosacral joints. The contribution of the hips and lumbosacral joint torques to pelvic rotation was subsequently calculated, with joint force powers indicating the rate of mechanical energy transfer between segments across joint centres calculated for both hip joints. The kinetic analysis indicated that the lumbosacral torsional torque contributed significantly to pelvic rotation. Additionally, the pelvic rotation exerted anterior–posterior joint forces on the hips, contributing to the large positive joint force power at the hip of the stance leg. These hip joint force powers assisted in motion recovery during sprinting. In conclusion, the lumbosacral torsional torque might contribute to the recovery motion in sprinting through application of the anterior–posterior joint forces at the hip joints via pelvic rotation.     

我国体育赞助市场诚信缺失的原因及维护对策

从体育赞助市场诚信缺失的原因入手,全面分析我国体育赞助市场诚信缺失的表现,并对我国体育赞助市场诚信缺失的行为进行剖析,在此基础上针对我国体育赞助市场中的诚信缺失行为提出针对性的措施.研究认为我国体育赞助市场法制建设落后于发展需求,体育赞助市场各关联方对诚信重要性认识不足.目前,需完善法律法规,建设强有力的道德约束机制,才能有效改进我国体育赞助市场的诚信环境,不断促进我国体育赞助市场的健康有序发展.     

The mirror’s curse: Weight perceptions mediate the link between physical activity and life satisfaction among 727,865 teens in 44 countries

Purpose:The present study aimed to examine the link between physical activity(PA)and life satisfaction in a large international study of adolescents.We also aimed to test whether overweight and underweight perceptions act as mediators and whether age and sex acted as moderators.Methods:For this purpose,we analyzed data from the Health Behavior in School-aged Children study,which comprises 727,865 observations from 44 nations at 4 measurement occasions.Results:Multilevel analyses revealed a positive link between PA and life satisfaction.In addition,underweight and overweight perceptions mediated the effect of PA on life satisfaction.We further found that age and sex acted as moderators.In older adolescents,stronger effects were found in the links between PA and life satisfaction,PA and overweight perception,and both weight perceptions and life satisfaction.In addition,in female adolescents,the link between overweight perception and life satisfaction was stronger.Conversely,the links between PA and both weight perceptions were stronger for boys.Conclusion:The results suggest that weight perception explains part of the relationship between PA and life satisfaction in adolescents and that these effects vary as a function of age and sex.     

The role of upper torso and pelvis rotation in driving performance during the golf swing

While the role of the upper torso and pelvis in driving performance is anecdotally appreciated by golf instructors, their actual biomechanical role is unclear. The aims of this study were to describe upper torso and pelvis rotation and velocity during the golf swing and determine their role in ball velocity. One hundred recreational golfers underwent a biomechanical golf swing analysis using their own driver. Upper torso and pelvic rotation and velocity, and torso-pelvic separation and velocity, were measured for each swing. Ball velocity was assessed with a golf launch monitor. Group differences (groups based on ball velocity) and moderate relationships (r > or = 0.50; P < 0.001) were observed between an increase in ball velocity and the following variables: increased torso-pelvic separation at the top of the swing, maximum torso-pelvic separation, maximum upper torso rotation velocity, upper torso rotational velocity at lead arm parallel and last 40 ms before impact, maximum torso-pelvic separation velocity and torso-pelvic separation velocity at both lead arm parallel and at the last 40 ms before impact. Torso-pelvic separation contributes to greater upper torso rotation velocity and torso-pelvic separation velocity during the downswing, ultimately contributing to greater ball velocity. Golf instructors can consider increasing ball velocity by maximizing separation between the upper torso and pelvis at the top of and initiation of the downswing.     

中外花样滑冰双人滑抛后外结环3周跳技术对比

抛跳技术是我国双人滑的优势技术,通过对中外选手抛后外结环3周跳的技术进行对比,找出我国抛跳技术的特殊性,为双人滑选手提供技术参考.     

The influence of Cardan rotation sequence on angular orientation data for the lower limb in the soccer kick

Abstract

The influence of the Cardan rotation sequence on the orientation angles for joints is well known but has not been explored for dynamic sports movements. The purpose of this study is to establish the influence of Cardan rotation sequence on the orientation angles of the ankle, knee, and hip of the support leg and pelvis during dynamic sports movements, typified by a maximal instep kick in soccer. We found that: (a) the X (flexion/extension) axis rotations provide data that are robust for any sequence used other than the YXZ sequence, although the Y (abduction/adduction) and Z (internal/external) axes rotations are variable in both shape and offset magnitude; (b) the preferred rotation sequence is either XYZ or XZY for dynamic sports movements, although for the soccer kick the XYZ rotation sequence has been widely used and so this is recommended as a standard; and (c) most uncertainties exist in the Y and Z axes and are most apparent at the beginning of the movement. Where uncertainty exists in identifying Y and Z axes orientations, the integrated angular velocity may be considered as an alternative to determine the relative changes in segment orientation.     

Shoulder 3D range of motion and humerus rotation in two volleyball spike techniques: injury prevention and performance

Repetitive stresses and movements on the shoulder in the volleyball spike expose this joint to overuse injuries, bringing athletes to a career threatening injury. Assuming that specific spike techniques play an important role in injury risk, we compared the kinematic of the traditional (TT) and the alternative (AT) techniques in 21 elite athletes, evaluating their safety with respect to performance. Glenohumeral joint was set as the centre of an imaginary sphere, intersected by the distal end of the humerus at different angles. Shoulder range of motion and angular velocities were calculated and compared to the joint limits. Ball speed and jump height were also assessed. Results indicated the trajectory of the humerus to be different for the TT, with maximal flexion of the shoulder reduced by 10 degrees, and horizontal abduction 15 degrees higher. No difference was found for external rotation angles, while axial rotation velocities were significantly higher in AT, with a 5% higher ball speed. Results suggest AT as a potential preventive solution to shoulder chronic pathologies, reducing shoulder flexion during spiking. The proposed method allows visualisation of risks associated with different overhead manoeuvres, by depicting humerus angles and velocities with respect to joint limits in the same 3D space.     

Differences in trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes

ABSTRACT

Although polo is a well-known equestrian sport, it is fundamentally misunderstood. The purpose of this study was to examine trunk and upper extremity kinematics and segmental velocities during the offside forehand polo swing between male and female athletes. Ten female and 17 male professional polo athletes volunteered. An electromagnetic tracking system collected kinematic data at 100 Hz while participants performed three offside forehand polo swings from a stationary wooden horse. One-way ANOVAs revealed statistically significant differences (p<0.05) in all kinematic variables and segmental velocities. Specifically, males exhibited a greater mean difference (MD=23°) of trunk flexion at take away (TA) and top of backswing (TOB)(MD=29°) trunk lateral flexion at ball contact (BC)(MD=23°), trunk rotation at TA(MD=97°) and TOB(MD=118°), shoulder abduction at TOB(MD=64°), and shoulder elevation at TOB(MD=13°) and BC(MD=40°). Females displayed greater trunk rotation at BC(MD=91°), shoulder elevation at TA(MD=19°), and elbow flexion at TA(MD=90°). Additionally, females generated greater segmental velocities early in the swing, while the males generated velocity later. The movement patterns observed amongst the males suggest energy is being transferred more efficiently along the kinetic chain, thus more efficient swing mechanics, but further investigation into the role of the trunk and lumbopelvic-hip complex in reference to the polo swing is warranted.     

An analysis of practice activities and instructional behaviours used by youth soccer coaches during practice: Exploring the link between science and application

Abstract

We examined the practice activities and instructional behaviours employed by 25 youth soccer coaches during 70 different practice sessions. We evaluated the extent to which these activities and behaviours differ from those shown in contemporary research to best facilitate skill acquisition. Nine coaches worked with the under-9 years age group and eight coaches each with the under-13 and under-16 years age groups; nine of those coaches were employed at the elite level, nine at the sub-elite level, and seven at the non-elite level. Coaches had players spend more time in activities that were deemed less relevant to soccer match performance, termed “training form” (e.g. physical training, technique and skills practices), than activities deemed more relevant, termed “playing form” (e.g. small-sided/conditioned games and phase of play activities). Coaches provided high levels of instruction, feedback, and management, irrespective of the activity in which players engaged. Few differences in practice activities and instructional behaviours were reported across skill and age groups, implying the absence of any notable age- or skill-related progression. Findings are discussed with reference to recent research in the areas of skill acquisition, motor learning, and expert performance.     

小抡臂扣球、大抡臂扣球和屈臂扣球对击球速度影响的研究

通过对两种扣球动作击球瞬时速度的定量化研究和公式推导,从理论上说明在排球扣球中,抡臂扣球动作的击球速度快于屈臂动作。     

课堂:研究性学习的主阵地

研究性学习是以培养学生自主探索精神为特征的一种教学方式,其主阵地在课堂。只有课堂的学习方式发生变革,才能有效地促进学生研究能力的发展。