质点组内力的功改变质心动能的条件     

田志川 《通化师范学院学报》2003,24(6):25-26

讨论了质点组内力的功是可以改变质心动能的，以及所满足的条件．  相似文献   

A comparison of methods to determine bilateral asymmetries in vertical leg stiffness     

Sean J. Maloney  Iain M. Fletcher  Joanna Richards 《Journal of sports sciences》2016,34(9):829-835

Whilst the measurement and quantification of vertical leg stiffness (K_vert) asymmetry is of important practical relevance to athletic performance, literature investigating bilateral asymmetry in K_vert is limited. Moreover, how the type of task used to assess K_vert may affect the expression of asymmetry has not been properly determined. Twelve healthy males performed three types of performance tasks on a dual force plate system to determine K_vert asymmetries; the tasks were (a) bilateral hopping, (b) bilateral drop jumping and (c) unilateral drop jumping. Across all the three methods, K_vert was significantly different between compliant and stiff limbs (P < 0.001) with a significant interaction effect between limb and method (P = 0.005). Differences in K_vert between compliant and stiff limbs were ?5.3% (P < 0.001), ?21.8% (P = 0.007) and ?15.1% (P < 0.001) for the bilateral hopping, bilateral drop jumping and unilateral drop jumping methods, respectively. All the three methods were able to detect significant differences between compliant and stiff limbs, and could be used as a diagnostic tool to assess K_vert asymmetry. Drop jumping tasks detected larger K_vert asymmetries than hopping, suggesting that asymmetries may be expressed to a greater extent in acyclic, maximal performance tasks.  相似文献   

Dribbling determinants in sub-elite youth soccer players     

Matteo Zago  Andrea Gianluca Piovan  Isabella Annoni  Daniela Ciprandi  F. Marcello Iaia 《Journal of sports sciences》2016,34(5):411-419

Dribbling speed in soccer is considered critical to the outcome of the game and can assist in the talent identification process. However, little is known about the biomechanics of this skill. By means of a motion capture system, we aimed to quantitatively investigate the determinants of effective dribbling skill in a group of 10 Under-13 sub-elite players, divided by the median-split technique according to their dribbling test time (faster and slower groups). Foot-ball contacts cadence, centre of mass (CoM), ranges of motion (RoM), velocity and acceleration, as well as stride length, cadence and variability were computed. Hip and knee joint RoMs were also considered. Faster players, as compared to slower players, showed a 30% higher foot-ball cadence (3.0 ± 0.1 vs. 2.3 ± 0.2 contacts · s^?1, P < 0.01); reduced CoM mediolateral (0.91 ± 0.05 vs. 1.14 ± 0.16 m, P < 0.05) and vertical (0.19 ± 0.01 vs. 0.25 ± 0.03 m, P < 0.05) RoMs; higher right stride cadence (+20%, P < 0.05) with lower variability (P < 0.05); reduced hip and knee flexion RoMs (P < 0.05). In conclusion, faster players are able to run with the ball through a shorter path in a more economical way. To effectively develop dribbling skill, coaches are encouraged to design specific practices where high stride frequency and narrow run trajectories are required.  相似文献   

社区居家养老服务中心体育服务需求与供给研究——以武汉市为例     

代方梅  刘亚奇  杨双  王靖  徐妍 《湖北体育科技》2016,(11):941-944

运用文献资料法、问卷调查法、数理统计法等,对武汉市社区居家养老服务中心的体育服务需求与供给现状进行研究。研究表明:社区老年人有较强的参与体育活动愿望,且参与体育活动在时段选择、时间长度、时间频率、活动强度等方面有着自身的规律;而养老服务中心的体育服务在场地设施、健身指导、信息宣传等方面与老年人的需求存在差距。建议:社会转型期的社区居家养老服务中的体育服务应做到体育服务供给主体多元化、体育服务内容多样化、体育服务人员专业化、体育志愿服务常态化。  相似文献   

大众文化的兴起     

宋巍 《黑龙江教育学院学报》2008,27(3):100-102

“大众文化”作为一个20世纪新兴的文化现象,有着独特的内涵和特征,对于这一文化现象兴起的原因历来众说纷纭,大众文化兴起的原因主要表现为：（1）科技时代机械复制技术的成果;（2）大众精神层面需求的滋生推进了这一文化现象的产生与发展;（3）产业利润的驱使也推动了这一现象的产生。  相似文献   

对成人心血管机能健康评价的探讨     

朱长征  殷川 《德州学院学报》2003,19(4):87-91

对德州市成人的心血管机能指标：心率、收缩压、舒张压、台阶指数进行分析与评价，结果为下等和差等、研究认为健康意识差、膳食结构不合理、运动习惯差、缺少体育文化氛围是造成现状的重要原因，针对群体状况提出“自我感觉练习法”和几项对策与建议，以指导健身练习。  相似文献   

物理化学实验大循环教学方法初探   总被引：3，自引：0，他引：3  

董丽红  王海燕 《通化师范学院学报》2004,25(2):69-70

探讨了在物理化学实验大循环实验中如何充分利用有限的课堂时间和实验设备完成实验要求的教学方法，这些方法也适用于其他学科的循环实验。  相似文献   

高等教育大众化质量问题浅探     

彭旭 《嘉应学院学报》2002,20(5):87-90

中国高等教育大众化的临近使得高等教育的质量问题日益成为人们关注的热点。本文主要从微观即学校内部的角度来分析影响高等教育质量的原因并从五个方面提出了解决办法。  相似文献   

火焰原子吸收光谱法测定废水中不同价态铬的含量   总被引：1，自引：0，他引：1  

李淑新  许明远  马淑珍  曹继福 《唐山师范学院学报》2002,24(2):33-35

建立了火焰原子吸收光谱法测定不同价态铬含量的方法。该方法的检出限为0.029mg·L-1;相对标准偏差为0.54%;平均加标回收率为99.3%;利用此分析方法测定了废水中不同价态铬的含量,结果令人满意。  相似文献   

大体积混凝土温度应力造成裂缝的控制     

ZHENG You wei 《福建工程学院学报》2001,(Z1)

分析大体积砼温度裂缝 ,提出降低温度应力、防止大体积砼裂缝几项措施  相似文献