Could knee joint mechanics during the golf swing be contributing to chronic knee injuries in professional golfers?

ABSTRACT

Full three-dimensional movements and external moments in golfers’ knees and the possible involvement in injuries have not been evaluated using motion capture at high sample frequencies. This study measured joint angles and external moments around the three anatomical axes in both knees of 10 professional golfers performing golf drives whilst standing on two force plates in a motion capture laboratory. Significant differences were found in the knee joint moments between the lead and trail limbs for the peak values and throughout all stages during the swing phase. A significantly higher net abduction moment impulse was seen in the trail limb compared with the lead limb (?0.518 vs. ?0.135 Nms.kg^?1), indicating greater loading over the whole swing, which could contribute to knee lateral compartment or anterior cruciate ligament injuries. A significant correlation (r = ?0.85) between clubhead speed at ball contact and maximum joint moment was found, with the largest correlations being found for joint moments at the top of the backswing event and at the end of the follow-through. Therefore, although knee moments can contribute to high clubhead speeds, the large moments and impulses suggest that they may also contribute to chronic knee injuries or exacerbate existing conditions.     

对中学篮球教学中重视学生“球感”训练的实验研究

本文通过对学生进行“球感”的训练 ,提高了学生对篮球运动中的控制球和支配球的能力 ,并令一些平时不怎么喜爱篮球运动的学生也乐意参加了 ,提高了学生的身体素质、终身体育意识和锻炼的习惯。     

论终身教育思想对体育课程改革的影响

为了适应现代社会的快速发展 ,人类改变了将人生划分为学习和工作两个阶段的观念 ,产生了终身教育的思想。终身教育思想又对教育的组成部分———体育产生影响 ,促使了终身体育思想的产生。终身体育思想对体育课程改革起到十分重要的影响作用 ,主要表现在对体育课程目标、体育教学内容、体育教学模式和体育教学评价等方面改革的影响 ,使改革充分体现了体育课程为终身体育打基础的思想     

试论排球主客场赛制运行特点及赛前训练

本文结合排球新赛制的运行特点，对主客场赛制的周期训练理论、赛前训练的几个训练学问题进行了初步的研究。     

SciELO对发展中国家开放存取期刊建设的启示

本文对科技在线电子图书馆（SciELO）的开放存取期刊进行了深入、具体的调查与分析，包括对学科分布、影响因子、即时因子和半衰期进行质量评价研究，以对发展中国家开放存取期刊建设有所启示。     

网络链接分析研究进展

本文对网络链接分析研究的进展情况作了较为全面、详细的介绍，并分析了目前网络链接分析研究中存在的问题。     

Impact Factors and the Central Limit Theorem: Why citation averages are scale dependent

Citation averages, and Impact Factors (IFs) in particular, are sensitive to sample size. Here, we apply the Central Limit Theorem to IFs to understand their scale-dependent behavior. For a journal of n randomly selected papers from a population of all papers, we expect from the Theorem that its IF fluctuates around the population average μ, and spans a range of values proportional to $\sigma /\sqrt{n}$, where σ² is the variance of the population's citation distribution. The $1/\sqrt{n}$ dependence has profound implications for IF rankings: The larger a journal, the narrower the range around μ where its IF lies. IF rankings therefore allocate an unfair advantage to smaller journals in the high IF ranks, and to larger journals in the low IF ranks. As a result, we expect a scale-dependent stratification of journals in IF rankings, whereby small journals occupy the top, middle, and bottom ranks; mid-sized journals occupy the middle ranks; and very large journals have IFs that asymptotically approach μ. We obtain qualitative and quantitative confirmation of these predictions by analyzing (i) the complete set of 166,498 IF & journal-size data pairs in the 1997–2016 Journal Citation Reports of Clarivate Analytics, (ii) the top-cited portion of 276,000 physics papers published in 2014–2015, and (iii) the citation distributions of an arbitrarily sampled list of physics journals. We conclude that the Central Limit Theorem is a good predictor of the IF range of actual journals, while sustained deviations from its predictions are a mark of true, non-random, citation impact. IF rankings are thus misleading unless one compares like-sized journals or adjusts for these effects. We propose the Φ index, a rescaled IF that accounts for size effects, and which can be readily generalized to account also for different citation practices across research fields. Our methodology applies to other citation averages that are used to compare research fields, university departments or countries in various types of rankings.     

The influence of shoe drop on the kinematics and kinetics of children tennis players

This study investigated the immediate effects of reducing the shoe drop (i.e. the difference between the heel and the forefoot height) on the kinematics and kinetics of the lower extremities of children tennis players performing a tennis-specific movement. Thirteen children tennis players performed a series of simulated open stance forehands wearing 3 pairs of shoes differing only in the drop: 0 (D0), 6 (D6) and the control condition of 12?mm (D12). Two embedded forceplates and a motion capture system were used to analyse the ground reaction forces and ankle and knee joint angles and moments of the leading lower limb. In D6 compared with D12, the peak impact force was reduced by 24% (p?=?.004) and the ankle was less dorsiflexed at foot strike (p?=?.037). In D0 compared with D12, the peak impact force was reduced by 17% (p?=?.049), the ankle was less dorsiflexed at foot strike (p?=?.045) and the knee was more flexed at foot strike (p?=?.007). In addition, 4 out of 13 participants (31%) presented a forefoot strike pattern for some of the trials in D0. No difference was observed across shoe conditions for the peak knee extensor moment (p?=?.658) or the peak ankle plantarflexor moment (p?=?.071). The results provide preliminary data supporting the hypothesis that for children tennis players, using a 6-mm lower shoe drop might reduce heel impact forces and thus limit potentially impact-related injuries.     

Hydrogenation properties of mechanically milled Mg2Nio.8Cr0.2-CoO/Al2O3 composites

Mg2Ni0.8Cr0.2-x wt.% CoO/Al2O3 (x=0.5, 1, 2 and 3) composites were prepared by mechanically milling sintered Mg2Ni0.8Cr0.2 alloy and CoO/Al2O3 compound for 45 h. The addition of CoO/Al2O3 compound resulted in the good kinetics properties of hydriding/dehydriding reaction of the composites. The composite with 1.0 wt.% CoO/Al2O3 catalyst could reach the maximum hydrogen absorption capacity (2.9 wt.%) within 5 min at 393 K under H2 pressure of 4 MPa, and can desorb rapidly at 493 K. The decomposition and synthesis of hydrogen molecule on Mg2Ni0.8Cr0.2 alloy surface was promoted by addition of CoO/Al2O3 catalyst. In addition, the formation of metallic Ni particles, strain and defects during the ball milling process also resulted in the improved hydrogenation performance of Mg2Ni-based alloys.     

上海世博交流影响力的网络模型

基于上海世博会对世界人民之间交流的影响力评价问题,建立了以国家和上海世博会为结点的网络模型,定义了世博交流影响力和未与中国建交的国家参展的交流影响力.分析显示:世博交流影响力随各参展国的投入和参展国数目的增加而增大;没有世博结点的网络交流状态越好,上海世博会的影响力越小.最后,通过数值算例验证上述结论.