竞技蹦床落网缓冲与蹬伸压网阶段矛盾体的力学分析

采用文献资料法、观察法及力学分析法,运用机械能守恒、运动学原理和冲量定理,分析了运动员落网缓冲与蹬伸展体过程。结果发现,入网缓冲前身体姿势的固定,对落网缓冲阶段和蹬伸压网阶段网下降的深度有不同的影响。因而寻求最佳的入网姿势,使落网缓冲和蹬伸压网阶段网下降的深度达到最大值是最追求绝对高度必须解决的一个问题。     

2019年夏季全国气候趋势展望

2019年春夏季,赤道中东太平洋将维持弱-中等强度厄尔尼诺（El Niño）。中国科学院大气物理研究所的全国气候趋势预测结果表明,预计2019年汛期（6—8月）,长江中下游以南大部分地区降水偏多,其中江南地区偏多2—5成,可能发生局地洪涝灾害;新疆北部、东北北部、四川东部和陕西南部等地降水正常略偏多。我国其他大部分地区降水正常略偏少,其中河套地区降水偏少2—5成。预计2019年登陆台风数正常略偏多。     

竞技太极拳中32系列难度动作单脚支撑落地稳定性训练探析

基于运动人体科学与运动训练学的相关理论，采用文献分析法、参与观察法、专家访谈法、问卷调查法等研究方法，对竞技太极拳中32系列难度动作落地单脚支撑技术特征进行理论分析和规律探讨。旨在从整体上系统地理解竞技太极拳中32系列难度动作各阶段间的关系，进而准确把握此类动作训练方法设计的理论基础，从而设计科学合理的训练方法，以提高运动员32系列难度动作落地单脚支撑的稳定性。研究得出，可通过SWISS球上俯卧转体等训练提高核心肌群的协调控制能力，BOSU球上单双腿直立或半蹲等练习增强髋关节肌群的离心收缩能力和协调控制能力，仰卧屈膝足跟夹SWISS球、手法松解等方式增强膝关节不同肌群的等长收缩、向心收缩、神经协调控制能力；通过踝关节PNF拉伸、跖趾关节PNF拉伸等增强足底非固有肌离心收缩能力和柔韧性，提高足底固有肌的神经协调能力。     

基层电大开放教育接轨农村、服务农民的和谐理念

致力于中国农民素质教育是电大系统实施网络教育必须担负的历史使命,基层电大接轨农村、服务农民是开放教育可持续发展的必然趋势。当今农村地区发展的不平衡现状和农民个体活动呈现的独立性、选择性、多变性等形态,决定了各地基层电大在向农村和农民实施开放教育的过程中,必须于教育观念、教育技术以及教育中远期目标上紧紧把持和谐的理念。     

Blocking landing techniques in volleyball and the possible association with anterior cruciate ligament injury

The number and type of landings performed after blocking during volleyball matches has been related to the potential risk of ACL injury. The aim of the present study was to determine whether gender affects the frequency of specific blocking landing techniques with potential risk of ACL injury from the perspective of foot contact and subsequent movement after the block used by volleyball players during competitive matches. Three matches involving four female volleyball teams (fourteen sets) and three matches involving four male volleyball teams (thirteen sets) in the Czech Republic were analyzed for this study. A Pearson chi-square test of independence was used to detect the relationship between gender and different blocking techniques. The results of the present study showed that gender affected single-leg landings with subsequent movement in lateral direction and double-leg landings. Although the total number of landings was lower for male athletes than for female athletes, a larger portion of male athletes demonstrated single leg landings with a subsequent movement than female athletes. Single leg landings with a subsequent movement have a higher potential risk of ACL injury.     

Effect of shoe wearing time and midsole hardness on ground reaction forces,ankle stability and perceived comfort in basketball landing

ABSTRACT

This study examined the effect of wearing time on comfort perception and landing biomechanics of basketball shoes with different midsole hardness. Fifteen basketball players performed drop landing and layup first step while wearing shoes of different wearing time (new, 2-, 4-, 6- and 8-week) and hardness (soft, medium and hard). Two-way ANOVA with repeated measures was performed on GRF, ankle kinematic and comfort perception variables. Increased wearing time was associated with poorer force attenuation and comfort perception during landing activities (p < 0.05). The new shoes had significantly smaller forefoot (2- and 4-week) and rearfoot peak GRF impacts (all time conditions) in drop landing and smaller rearfoot peak GRF impact (6- and 8-week) in layup; shoes with 4-week of wearing time had significantly better perceptions of forefoot cushioning, forefoot stability, rearfoot cushioning, rearfoot stability and overall comfort than the new shoes (p < 0.05). Compared with hard shoes, the soft shoes had better rearfoot cushioning but poorer forefoot cushioning (p < 0.05). Shoe hardness and wearing time would play an influential role in GRF and comfort perception, but not in ankle kinematics. Although shoe cushioning performance would decrease even after a short wearing period, the best comfort perception was found at 4-week wearing time.     

Skating

Technical evaluation in the sport of figure skating is characterized by a subjective marking system. Figure skating judges are responsible for quickly and accurately discerning the quality of technical elements as well as assigning a score to the overall aesthetic appearance of a performance. Traditionally, overall placement marks are assigned for the entire performance; however, the landing of a jump is widely acknowledged as one of the most critical elements of a skater's program. Therefore, our aims were to identify the biomechanical variables that contribute to technical success in executing landings and to establish whether landings rated as biomechanically optimal are also awarded high technical merit scores by judges. Ten nationally ranked competitive figure skaters were asked to execute on‐ice, double and triple revolution jumps and to try to land the jumps void of technical faults within a calibrated space. Data were collected at 60 Hz using standard three‐dimensional videography. Data reduction was done using the APAS system (Ariel Dynamics Inc). Concurrently, videotapes were viewed and evaluated by 42 accredited judges to determine the perceived technical quality of the landing performances. Judges were asked to evaluate the landing phase of each jump against a landing criteria document. A comparative criteria model was developed to facilitate an assessment of excellence in landing performances through both empirical and subjective analyses. Results of these analyses were twofold: a biomechanical profile of on‐ice landings was obtained, and on‐ice jump landing strategies rated by empirical evaluations were in agreement with judge's perceptions of the same performances.     

Statistical modelling of knee valgus during a continuous jump test

Landing with the knee in a valgus position is recognized as a risk factor for anterior cruciate ligament (ACL) injury. Using linear and non-linear regression analyses, the purpose of this study was to examine the correlation between two-dimensional (2D) knee valgus and three-dimensional (3D) knee kinematics measured during a jump landing task. Twenty-eight female collegiate athletes participated. All participants were required to perform a continuous jump test. The average maximum angles of abduction and internal tibial rotation during landing were measured using the Point Cluster Technique. Average peak knee valgus angle was measured using a 2D approach. Linear and non-linear regression analyses between 2D valgus and 3D knee abduction, and between 2D valgus and 3D internal tibial rotation, were performed. The R ² value between 2D valgus and 3D knee abduction was significantly different from zero and had a moderate correlation for all models, whereas the R ² value between 2D valgus and 3D internal tibial rotation was not significantly different from zero. The 2D approach could be used to screen a specific group of individuals for risk of ACL injury; however, using frontal plane 2D analysis of valgus motion to evaluate internal tibial rotation is not advised.     

Effects of mat characteristics on plantar pressure patterns and perceived mat properties during landing in gymnastics

Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction.     

课程改革需要“软着陆”吗？

查有梁教授在《论新课程改革的“软着陆”》一文提出了《对话》里的“八个误导”,指出这些误导表现出了西方后现代理论在中国课程改革中的一种思潮,因此得出课程改革需“软着陆”。查文对新课改“突变式”、“运动式”、“大跃进式”的非难,对新课改成果悲观的看法是站不住脚的,因此有必要就“误导”涉及的关于教育基本价值取向、基础学力观和知识观、课程实施观和教师角色转型、课程改革立足点与发展趋势等问题与查有梁教授进行商榷。