浅析我国业余拳击运动发展的制约因素

从形态、训练方法、普及范围等几个方面提出了目前制约中国业余拳击运动发展的因素,指出在目前的情况下,针对基层开展业余拳击的现状,从法律法规、训练体系、市场推广等方面解决问题,找出适合业余拳击发展的训练之路.     

Influence of longswing technique on the kinematics and key release parameters of the straddle Tkachev on uneven bars

Tkachev on uneven bars is a release and re-grasp skill performed using variations of preparatory longswing techniques; the reasons why different techniques are chosen remains unclear. This study examined kinematic and key release parameters specific to three distinct techniques with the aim of understanding the relative benefits of each. During two international artistic gymnastics competitions six arch, straddle and pike longswings preceding the straddle Tkachev were recorded using twin video cameras. Calibration and movement images were digitised and reconstructed using 3D DLT. Shoulder and hip angular kinematics, angular momentum and key release parameters were compared between techniques. In the arch longswing, the first and second hip functional phases began significantly earlier than the straddle or pike. No significant differences were established for release parameters although large effect sizes for horizontal release velocity and angular momenta about the mass centre and bar were reported between the arch and other two variants. Therefore, the arch variant may provide the opportunity to develop more complex combinations following the Tkachev. Providing insight into mechanical advantages of specific longswing techniques, and highlighting those that elicit desirable characteristics offers the potential to provide coaches with objective data on technique selection and ultimately skill development.     

Musculoskeletal demands of progressions for the longswing on high bar

Kinetic analyses of the chalked bar longswing on high bar and its associated progressions were used to explain musculoskeletal contributions during the performance of these skills. Data on four international male gymnasts performing three series of chalked bar longswings and eight progressions were recorded. Customized body segment inertia parameters, two-dimensional kinematics (50 Hz), and bar forces (1000 Hz) were used as input to inverse dynamic modelling. The analysis focused on the relative contributions of the knees, hips, and shoulders with root mean squared differences between the chalked bar longswing and the progressions being used to rank the progressions. Seventy per cent of the total work occurred between 200° and 240° of angular rotation in the longswing, 67% of which was contributed by the shoulders. The shoulders were also dominant in all progressions, with the largest such contribution occurring in the looped bar longswing with “no action”. The least similar progression was the looped bar pendulum swing, while the most similar was the chalked bar bent knee longswing. This study provides a useful means for ranking progressions based on their kinetic similarity to the chalked bar longswing and builds on earlier research in identifying that progressions can be classified into those similar in physical demand (kinetics) and those similar in geometry (kinematics).     

高职单片机应用课程理实一体化实践

如何打破理论教学和实践教学相分离的传统模式,一直是职业教学研究的重点课题。本文以单片机应用课程为例阐述了理实一体化课程计划开发、理实一体化教材编写、理实一体化教学场地建设及构建一体化的考核评价方式。     

对影响农村学校体育发展因素的初探

农村学校体育的重要性是不容置疑的,而在广大农村地区体育教育现状令人担扰.从经济发展水平、应试教育、管理机制等几方面探讨影响农村学校体育发展的因素,并从明确目的、完善评价体系、加强管理及投入等方面提出相应的对策与建议.     

高可靠内部局域网环境下联机编目及OPAC的实现

介绍在局域网环境下如何用天融信NGFW3000防火墙的NAT功能和端口映射功能保障联机编目和OPAC的实现。     

中国高新技术企业专利权对未来经营绩效影响的实证研究

专利权数量和经营绩效关系的研究大多采取同期的数据。公司积累的专利权数量对经营绩效的影响具有滞后性,进而提出了公司专利权数量对未来经营绩效影响的理论假设,并以我国高新技术产业上市公司为样本进行实证研究。实证分析的结果发现:高新技术上市公司拥有的专利权总数与公司未来业绩缺乏明显的相关关系。在各类型专利权指标中,只有发明专利对企业后续两年的经营绩效产生正向显著影响。     

Stance limb kinetics of older male athletes endurance running performance

The aim of this study was to examine the age-based, lower limb kinetics of running performances of endurance athletes. Six running trials were performed by 24 male athletes, who were distinguished by three age groupings (S35: 26–32 years, M50: 50–54 years, M60+: 60–68 years). Lower limb coordinate and ground reaction force data were collected using a nine camera infra-red system synchronised with a force plate. A slower anteroposterior (M ± SD S35 = 4.13 ± 0.54 m/s: M60+ = 3.34 ± 0.40 m/s, p < 0.05) running velocity was associated with significant (p < 0.05) decreases in step length and discrete vertical ground contact force between M60+and S35 athletes. The M60+athletes simultaneously generated a 32% and 42% reduction (p < 0.05) in ankle joint moment when compared to the M50 and S35 athletes and 72% (p < 0.05) reduction in knee joint stiffness when compared to S35 athletes. Age-based declines in running performance were associated with reduced stance phase force tolerance and generation that may be accounted for due to an inhibited force–velocity muscular function of the lower limb. Joint-specific coaching strategies customised to athlete age are warranted to maintain/enhance athletes' dynamic performance.     

Kinematic changes during learning the longswing on high bar

The purpose of this study is to provide evidence of technique changes during learning a sports-specific skill, the looped bar longswing (LLS). Thirteen male participants with no previous high bar experience took part in a training study. Kinematic data were collected using a CODA motion analysis system (200 Hz) during eight weekly testing sessions. Analyses focused on the amplitude of swing and the functional phase (FP) actions, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical. Three groups were identified based on the number of sessions it took each participant to perform the LLS (G1: most successful, G2: intermediate, and G3: least successful). All participants were able to significantly increase swing amplitude over the training period (p < 0.05). For each participant the hip FP started significantly: later for G1, earlier for G2, and did not change for G3. Extension actions at the shoulders were dissimilar to those reported for elite gymnasts performing the longswing. The FP of the hips provides a mechanism to distinguish between the learners of different skill levels. The study has provided support for a single-subject design when investigating technique changes during learning.     

Modelling the flight of a soccer ball in a direct free kick

This study involved a theoretical and an experimental investigation of the direct free kick in soccer. Our aim was to develop a mathematical model of the ball's flight incorporating aerodynamic lift and drag forces to explore this important 'set-play'. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ball's spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m x s(-1), the ball's initial elevation must be constrained between 16.5 degrees and 17.5 degrees and the ball kicked with almost perfect sidespin.