Mechanisms of anterior cruciate ligament injuries in elite women’s netball: a systematic video analysis

This study involved a systematic video analysis of 16 anterior cruciate ligament (ACL) injuries sustained by elite-level netball players during televised games in order to describe the game situation, the movement patterns involved, the player’s behaviour, and a potential injury mechanism. Eight of the ACL injuries were classified as “indirect contact” and eight as “non-contact”. Two common scenarios were identified. In Scenario A the player was jumping to receive or intercept a pass and whilst competing for the ball experienced a perturbation in the air. As a result the player’s landing was unbalanced with loading occurring predominantly on the knee of the injured side. In Scenario B the player was generally in a good position at ground contact, but then noticeably altered the alignment of the trunk before the landing was completed. This involved rotating and laterally flexing the trunk without altering the alignment of the feet. Apparent knee valgus collapse on the knee of the injured side was observed in 3/6 Scenario A cases and 5/6 Scenario B cases. Players may benefit from landing training programmes that incorporate tasks that use a ball and include decision-making components or require players to learn to cope with being unbalanced.     

关于田径教材中跑的技术原理某些理论问题的探讨

教材中，跑的周期阶段划分方法，脱离了跑步技术的实际应用，没有达到便于分析技术动作的目的，提出新的划分观点是基于两腿周期动作同时具有对应性、同步性和反方向性的特征，把单腿动作周期划分为折叠后摆、前摆、下压着地缓冲、后蹬四个阶段，有利于双腿动作协调配合的动力学特征分析。支撑腿着地缓冲时，髋关节不是主动弯曲，而是积极伸展；踝、膝关节的弯曲缓冲是被动的，而不是主动的。“踝、膝、髋关节主动弯曲缓冲”的技术要求是不妥当的，其结果必然导致缓冲时间的延长，而不是“缩短缓冲时间”。     

嫦娥三号软着陆轨道设计及最优控制策略

对于嫦娥三号着陆轨道,根据阶段的不同状况逐一处理：①着陆准备阶段：由物理分析得到轨道方程。②主减速阶段：建立适当坐标系,求出该阶段抛物线的三次多项式方程。③快速调整阶段：经过多重分析确定下降方案。④粗避障段：经过划分板块设定阈值,确定降落范围。⑤精避障段：用同样的原理确定最终降落地点。⑥缓速下降阶段：视作自由落体运动。对最优控制策略问题,对软着陆过程进行受力分析,考虑着陆过程中推进力、单位时间燃耗和飞行速度随着飞行时间的变化情况,从而得出控制策略。     

论新课程改革的“软着陆”

新课程改革需要“软着陆”,是指课改的进程要减慢速度,课改的实施要稳步成功。钟启泉教授的一篇对新课程改革的总结性《对话》提出的一系列观点,都不利于课程改革的“软着陆”,是对课程改革的误导。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。新课程改革如何“软着陆”,这需要以“科学发展观”为指导。     

关于羽毛球双打发球落点变化及稳定性的技术分析

在羽毛球双打比赛中发球点有相当重要的位置。规则规定没有发球权就没有得分。发球质量的好坏决定着比赛的胜负。而发球落点的变化性是高水平双打选手发球技术的重要标志。     

2018年夏季全国气候趋势展望

中科院大气所ENSO预测结果显示,2018年夏季（6—8月）,赤道中东太平洋海温将处于中性状态。中科院大气所的全国气候趋势预测结果表明,2018年夏季（6—8月）,全国总体形势为降水趋于常年。部分地区可能呈现偏多或偏少的情况。具体为,东北东部、华北大部、西北地区东部、江南大部、华南北部和中部降水正常略偏多,其中河套地区降水偏多2—5成,可能发生局地洪涝。我国其他大部分地区降水正常略偏少。登陆台风数正常偏少。     

Shock and impact reduction in moderate and strenuous landing activities

Shock reduction has been well studied in moderate activities such as walking and running. However, there is a clear lack of research concerning shock wave transmission and reduction in more strenuous landing activities. In this study, we examined the impact of shock transmission and reduction in landing activities with varied mechanical demands. Ten active males were recruited for the study. They performed five successful step-off landing trials from each of five heights: 30, 45, 60, 75, and 90 cm. Right sagittal kinematics, ground reaction forces, and acceleration were recorded simultaneously. Impact frequencies were analysed using a discrete Fast Fourier Transform and power spectral density was computed. Increased range of motion for the ankle, knee, and hip joints was observed at higher landing heights. The peaks of the vertical ground reaction force, forehead and tibial accelerations, and eccentric muscle work by lower extremity joints were increased with increased landing heights. The peak head power spectral density was severely attenuated at higher frequencies but the peak tibia power spectral density did not demonstrate this trend. Shock reduction showed increased reduction at higher frequencies, but minimal changes across five landing heights. Unlike the responses observed for walking and running, the shock reduction did not show significant improvement with elevated mechanical demands.     

Vertical Ground Reaction Forces of Children during One- and Two-Leg Rope Jumping

Abstract

Sport offers opportunities for children to identify and resolve moral issues. Moral issues in sport have primarily been studied from the researcher's perspective, with the child's perspective relatively ignored. Thus, the purpose of this study was to explore the nature and content of the issues children experienced in sport. Interview participants consisted of 7 boys and 8 girls ranging in age from 10 to 12 years (M = 11.6 years, SD = 1.7) who had competitive youth sport experience. An inductive content analysis revealed that children identified issues surrounding three overall dimensions concerning fairness of adult's actions, negative game behaviors, and negative team behaviors. Specific examples of issues included unfair actions by coaches, disrespecting opponents, and selfish behavior in practice. The self-identified issues both confirmed and expanded upon the content found in hypothetical moral dilemmas in sport.     

试论跑的支撑时期着地缓冲与后蹬阶段的止、起点的划分

我国主要田径教材关于跑的周期阶段的划分存在着多种理论,其中对支撑时期着地缓冲与后蹬起、止点的划分也存在较大分歧.为解决该问题,运用信息技术为主的方法,对当今世界男子100 m记录保持者博尔特的有关技术参数进行分析,提出了着地缓冲与后蹬止、起点的新划分方法,指出划分应具体量化,以期为短跑技术分析的实际运用提供理论依据.     

高、低帮篮球鞋对落地时踝关节稳定及肌肉功能影响的研究

目的:探讨高、低帮篮球鞋对落地时踝关节内翻的运动学、地面反作用力及下肢主要肌群活动的影响,尝试理解高、低帮篮球鞋与踝关节落地稳定之间的关系;方法:13名受试者分别穿着高、低帮篮球鞋,手抓杠悬于空中,从40 cm高度分别垂直下落至内翻15°、内翻30°、内翻25°伴随跖屈10°(25°+10°)、内翻25°伴随跖屈20°(25°+20°)的倾斜面上,分析其踝关节运动学、地面反作用力及小腿主要外翻和背屈肌群(胫骨前肌、腓骨长肌和腓骨短肌)的肌电活动;结果:高、低帮鞋对内翻角度的变化、最大内翻角速度和地面垂直及水平冲击力没有显著影响;在15°倾斜面时,穿着高帮鞋出现预激活时间比低帮鞋晚(P<0.05),同时,在15°和25°+20°下腓骨长肌和腓骨短肌落地前50 ms的平均振幅更小(P<0.05);结论:选取的高帮鞋对踝关节的运动学和冲击力的改变不显著,但却在一定程度上影响了周围肌肉的预激活,对限制踝关节活动起到了积极的作用.