下肢肌在踏跳动作中的储能     

周强 《浙江体育科学》2000,22(1):44-47,64

下肢肌肉储能大小和再利用率反映了运动员下肢肌的力量素质和动作技术的优劣 ,也是评定运动员下肢肌肉力量素质的动力学指标。我们采用高速摄影和三维测力 ,对 6名运动员在跳跃踏跳中 ,下肢肌肉的储能大小、负功利用率及其影响因素进行了研究。试验结果表明 :1 .外负荷变化时 ,踏跳缓冲结束瞬时肌肉的力值不同 ,且存在极值 ,此极值的大小与运动员的力量素质有关。 2 .下肢肌肉的储能与缓冲结束瞬时的力值之间有一定的比例关系 ,当肌肉受到一个最佳的拉伸力时 ,肌肉储能最多。 3.肌肉在向心收缩过程 ,对其在离心收缩过程中肌肉所做的负功的利用率 ,随着外负荷的增大而降低  相似文献   

地壳运动原动力的新假说     

王春华 《衡阳师范学院学报》2014,(1):111-114

董妙先的《多四季论》假说,揭示了地球表面存在大冷大热的效应变化。这种巨大冷热差异造成地壳岩层的热胀冷缩力就是地壳运动的原动力。当异常低温期,地壳岩层大规模冷缩开裂,形成海洋;当异常高温期,地壳板块大规模膨胀扩展,推挤出板块周边的山脉。地球表面现有的两大山脉是在中生代末的高温期由两大古陆膨胀扩展拼接成联合大陆时推挤而成;三大海洋是新生代寒冷期由联合大陆冷缩破裂而成。先有两大山脉,后有三大海洋。  相似文献   

便携式肌肉等张收缩关节功率曲线测试系统的研制及等速肌力测试验证   总被引：1，自引：0，他引：1  

李林  纪仲秋 《成都体育学院学报》2014,(9)

采用惯性传感技术和无线蓝牙采集技术研制了便携式肌肉等张收缩关节功率曲线测试系统,详细说明了该测试系统的内部结构和数据处理方法。该测试系统采用三次样条插值法插值,能够方便准确的测试不同负重下肌肉等张收缩的最大峰值关节功率曲线,能方便携带到课堂和操场上进行教学和测试,在运动员选材、日常力量训练等多个方面都有非常重要的应用。采用BIODEX等速肌力测试系统对膝关节关节功率进行测试分析,测试结果和本测试系统获得的结果通过配对样本T检验方法,双侧显著性水平大于0.05,提示二者没有显著差异,验证了本系统的数据有效性。  相似文献   

Relationships between functional movement screen scores,maturation and physical performance in young soccer players     

Rhodri S. Lloyd  Jon L. Oliver  John M. Radnor  Benjamin C. Rhodes  Avery D. Faigenbaum  Gregory D. Myer 《Journal of sports sciences》2015,33(1):11-19

The purpose of this study was to examine relationships between functional movement screen scores, maturation and physical performance in young soccer players. Thirty males (11–16 years) were assessed for maturation, functional movement screen scores and a range of physical performance tests (squat jump, reactive strength index protocol and reactive agility cut). Older players significantly outperformed younger participants in all tests (P < 0.05; effect sizes = 1.25–3.40). Deep overhead squat, in-line lunge, active straight leg raise and rotary stability test were significantly correlated to all performance tests. In-line lunge performance explained the greatest variance in reactive strength index (adjusted R² = 47%) and reactive agility cut (adjusted R² = 38%) performance, whilst maturation was the strongest predictor of squat jump performance (adjusted R² = 46%). This study demonstrated that variation of physical performance in youth soccer players could be explained by a combination of both functional movement screen scores and maturation.  相似文献   

sEMG feature analysis on forearm muscle fatigue during isometric contractions     

明东  王欣  徐瑞  邱爽  赵欣  綦宏志  周鹏  张力新  万柏坤 《天津大学学报(英文版)》2014,20(2):139-143

In order to detect and assess the muscle fatigue state with the surface electromyography(sEMG) characteristic parameters,this paper carried out a series of isometric contraction experiments to induce the fatigue on the forearm muscles from four subjects,and recorded the sEMG signals of the flexor carpi ulnaris.sEMG's median frequency(MDF) and mean frequency(MF) were extracted by short term Fourier transform(STFT),and the root mean square(RMS) of wavelet coefficients in the frequency band of 5—45 Hz was obtained by continuous wavelet transform(CWT).The results demonstrate that both MDF and MF show downward trends within 1 min; however,RMS shows an upward trend within the same time.The three parameters are closely correlated with absolute values of mean correlation coefficients greater than 0.8.It is suggested that the three parameters above can be used as reliable indicators to evaluate the level of muscle fatigue during isometric contractions.  相似文献   

Greater fatigability in knee-flexors vs. knee-extensors after a standardized fatiguing protocol     

Giuseppe Coratella  Sidney Grosprêtre  Philippe Gimenez  Laurent Mourot 《European Journal of Sport Science》2018,18(8):1110-1118

The present study aimed to investigate the effects of a standardized fatiguing protocol on central and peripheral fatigue in knee-flexors and knee-extensors. Thirteen healthy men (age: 23?±?3 years; height: 1.78?±?0.09 m; body-mass: 73.6?±?9.2?kg) volunteered for the present study. Maximal voluntary contraction (MVC), Electromyography (EMG) activity, voluntary activation level (VAL) as an index of central fatigue and twitch potentiation as an index of peripheral fatigue were measured before and after the fatiguing protocol. The fatiguing protocol consisted of a 0.6 duty-cycle to exhaustion (6?s isometric contraction, 4?s recovery) at 70% MVC. After the fatiguing protocol, MVC decreased in both (Effect-size (ES)?=?1.14) and knee-extensors (ES?=?1.14), and EMG activity increased in both knee-flexors (ES?=?2.33) and knee-extensors (ES?=?1.54). Decreases in VAL occurred in knee-flexors (ES?=?0.92) but not in knee-extensors (ES?=?0.04). Decreases in potentiation occurred in both knee-flexors (ES?=?0.84) and knee-extensors (ES?=?0.58). The greater central occurrence of fatigue in knee-flexors than in knee-extensors may depend on the different muscle morphology and coupled with a greater tolerance to fatigue in knee-extensors. The present data add further insight to the complicated knee-flexors-to-knee-extensors strength relationship and the mechanisms behind the different occurrence of fatigue.  相似文献   

一类广义压缩型映象的不动点     

朱元国 《赣南师范学院学报》1998,(3)

本文在完备度量空间中讨论了一类广义压缩型映象不动点的存在及唯一性,是Ｂａｎａｃｈ压缩原理的一种推广。  相似文献   

对一幅插图的补充     

蔡晶 《中学生物教学》1998,(3)

对一幅插图的补充九年义务教育三年制初级中学教科书《生物》第一册（上）Ｐ．１９图Ⅰ—６是细胞分裂过程图。笔者在教学中感到这幅图由于对细胞核的分裂未加体现,因而略显欠缺。书中原图如下：图１书中对图的说明是这样的：细胞分裂就是一个细胞分成两个细胞。简单地说...  相似文献   

短跑支撑阶段运动生物力学分析          下载免费PDF全文

施宝兴 《体育科研》2010,31(6):40-43

采用测力、高速录像及特殊的数据平滑处理方法研究短跑运动员途中跑技术的运动学和动力学特征,进行田径技术原理的探索。结果表明,支撑时期可以分为着地阶段和蹬伸阶段,蹬伸阶段可分前蹬,后蹬前段,后蹬后段。途中跑前蹬段是人体重心垂直方向向上加速的重要时刻,前蹬时下肢一定程度的垂直加速用力虽影响水平速度,但对提高垂直速度有积极意义,前蹬和后蹬前段是身体重心垂直向上加速运动的阶段。着地缓冲后的前蹬用力也是实现良好成绩的技术之一。途中跑着地和前蹬阶段失去的水平速度损失完全可以从后蹬中得到补充。着地点过近对前支撑阶段获得重要的垂直速度不利,支撑阶段离地前的20ms身体重心速度已经开始下降。  相似文献