Effect of different velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles     

Alejandro Pérez-Castilla  Paulino Padial  Antonio J. Morales-Artacho  Belén Feriche 《Journal of sports sciences》2018,36(12):1331-1339

This study compared the effects of two velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles. Twenty men were counterbalanced in two groups (VL10 and VL20) based on their maximum power capacity. Both groups used the same exercises, relative intensity and repetition volume, only differing in the velocity loss threshold of each set (VL10: 10% vs. VL20: 20%). Pre- and post-training assessments included an incremental loading test and a 15-m linear sprint to assess the force- and load-velocity relationships and athletic performance variables, respectively. No significant between-group differences (P > 0.05) were observed for the force-velocity relationship parameters (ES range = 0.15–0.42), the MPV attained against different external loads (ES range = 0.02–0.18) or the 15-m sprint time (ES = 0.09). A high between-participants variability was reported for the number of repetitions completed in each training set (CV = 30.3% for VL10 and 29.4% for VL20). These results suggest that both velocity loss thresholds induce similar changes on the lower-body function. The high and variable number of repetitions completed may compromise the velocity-based approach for prescribing and monitoring the repetition volume during a power-oriented resistance training program conducted with the countermovement jump exercise.  相似文献   

液滴撞击凹凸槽道表面液膜的动态演变     

周鑫  王宏  朱恂  陈蓉  廖强  丁玉栋 《中国科学院大学学报》2020,37(2):255-262

为研究固体表面结构对液滴撞击液膜后演变行为的影响规律，采用CLSVOF方法模拟液滴撞击不同尺寸槽道上的表面液膜的流动过程，获得不同槽道高度和宽度时液滴撞击液膜后的演变行为，探索撞击速度、液膜黏度和表面张力对撞击后液膜铺展行为、水花飞溅高度和二次液滴形成的影响。结果表明，槽道结构对液滴撞击液膜后的动态行为具有显著影响，随着槽道高度的增加，冠状水花厚度越薄，越容易产生二次液滴；随着液膜黏度的增大，则抑制冠状水花形成与二次液滴的产生；液膜表面张力减小时，射流更加明显，二次液滴数更多，飞溅现象提前，冠状水花消失时间延后。  相似文献   

Can changes in resistance exercise workload influence internal load,countermovement jump performance and the endocrine response?     

Daniel J Hiscock  Brian Dawson  Michael Clarke  Peter Peeling 《Journal of sports sciences》2018,36(2):191-197

This study examined the influence of differing volume load and intensity (%1 repetition maximum[%1RM]) resistance exercise workouts on session rating of perceived exertion (sRPE) countermovement jump (CMJ) performance and endocrine responses. Twelve participants performed a workout comprising four exercises (bench press, back squat, deadlift and prone bench pull) in randomised order as either power (POW); 3 sets × 6 repetitions at 45%1RM × 3 min inter-set rest, strength (ST); 3 sets × 3 repetitions at 90%1RM × 3 min inter-set rest, or hypertrophy (HYP); 3 sets × 10 repetitions at 70%1RM × 1 min inter-set rest in a randomised-crossover design. CMJ performance and endocrine responses were measured immediately pre-, post-, 12, 24, 48 and 72 h post-exercise. POW sRPE (3.0 ± 1.0) was lower than ST (4.5 ± 1.0) (P = 0.01), and both were lower than HYP (8.5 ± 1.0) (P = 0.01). Duration of CMJ decrement was longer (P ≤ 0.05) for HYP (72 h) compared to POW (12 h) and ST (24 h). Testosterone concentration was greater (P ≤ 0.05) immediately post-exercise in HYP compared to POW and ST. In conclusion, less inter-set rest, greater volume load and intensity (%1RM) may increase sRPE, duration of CMJ performance decrement and testosterone responses in resistance exercise.  相似文献   

中国的主要贸易伙伴和对外贸易地理方向研究     

杨扬 《湖北广播电视大学学报》2007,27(7):95-96

中国入世五年来,在世贸组织的框架下,中国的对外贸易实现了飞速发展。对外贸易地理方向又称对外贸易地区分布或国别结构,是指一定时期内各个国家或区域集团在一国对外贸易中所占有的地位。一国的对外贸易地理方向通常受经济互补性、国际分工的形式与贸易政策的影响。对外贸易地理方向,从地理上讲,也就是一国贸易伙伴的分布。中国主要的贸易伙伴既保持了相对较强的稳定性,也在各种因素的作用下悄然地出现着一些变化。本文试图通过对影响中国主要贸易伙伴变迁的这些因素加以分析,整体把握中国对外贸易地理方向的格局和发展趋势。  相似文献   

低年级学生数感培养的实践与思考     

赵妍 《天津教育》2021,(11):24-25

《义务教育数学课程标准(2011版)》提出了十个核心词,“数感”是其中一个,且位列第一,是教师在备课、研课、评课时常用的关键词。关于数感及学生数感的培养,许多专家、学者、一线教师已有了丰硕的理论及实践研究结果。相比之下,小学低年级的研究较之中高年级则单薄得多。然而数感作为一种自觉的行为,更应该从学生起步阶段加以培养,应渗透到数学学习的整个过程。  相似文献   

上海内河集装箱运量预测   总被引：2，自引：0，他引：2  

郑士源  刘晓峰  宗蓓华 《预测》2002,21(4):30-35

本文在对上海内河运输网络中各节点集装箱生成量进行预测的基础上，根据公路、水路的成本比较对各节点间集装箱的运量进行分流，得出了未来20年间上海内河网络中的集装箱运输量。从预测的结果可看出，随着内河集装箱运输条件的改善，内河集装箱运量占集装箱运输总量的比例逐渐上升，将成为上海国际航运中心不可缺少的集疏运方式。  相似文献   

新疆库车凹陷侏罗系多粒级黏土矿物分析方法及其对沉积-成岩环境的指示     

吴朝东  王琪琪冯雪 顾萧 《中国科技期刊研究》2007,23(7):1655-1663

本文选取库车坳陷侏罗系阿合组—齐古组的碎屑岩样品，利用Stokes原理，通过同步跟进与离心分析相结合的多粒级提取的方式提取不同粒径的黏土矿物，包括〉20μm；20μm～5μm；5μm～2μm；2μm～0．2μm和〈0．2μm。不同粒径组分的黏土矿物呈现出不同的型貌特征，在20～2μm范围内的样品中，自生黏土矿物少见，大量可见碎屑来源的黏土矿物，由于经过了长期的机械搬运，难见完整的晶型。在〈2μm的样品中大量存在自生黏土矿物，大量成集合体，同时也存在碎屑蚀变成因的黏土矿物。通过XRD方法定量分析了所分离出的不同粒径黏土矿物的相对含量，黏土粒径范围内的黏土矿物相对含量呈现些规律变化。碎屑伊利石含量有随着粒级的减小而减少的趋势，而自生伊利石和伊蒙混层只在2～0．2μm及0，2μm以下粒级才出现，并且集中在0．2μm以下粒级范围内；在古气候，沉积环境和母岩特性及分布基本一致的情况下，高岭石的分布有随着岩性的变粗呈现升高的趋势，而伊利石呈负相关关系。碎屑岩中黏土矿物的形貌特征表明，黏土矿物有陆源碎屑来源与自生两种成因，应用Decoform软件对0．2μm以下黏土矿物中不同成因的伊利石进行了计算，并就存在的比例与粒径的关系进行了讨论。黏土矿物组合揭示侏罗纪沉积环境由酸性环境向微碱性环境过渡，早侏罗世和中侏罗世早期为气候潮湿时期，高岭石的含量明显高于侏罗世晚期地层，恰克马克期到齐古期高岭石含量开始出现减小的趋势。从恰克马克期开始，气候缓慢向干旱变化，高龄石含量降低，而伊利石的平均含量明显增加，反映黏土矿物组合主要受沉积环境和成岩作用共同影响。  相似文献   

Two direct Tustin discretization methods for fractional-order differentiator/integrator   总被引：1，自引：0，他引：1  

Blas M. Vinagre  Ivo Petráš 《Journal of The Franklin Institute》2003,340(5):349-362

This paper deals with fractional calculus and its approximate discretization. Two direct discretization methods useful in control and digital filtering are presented for discretizing the fractional-order differentiator or integrator. Detailed mathematical formulae and tables are given. An illustrative example is presented to show the practically usefulness of the two proposed discretization schemes. Comparative remarks between the two methods are also given.  相似文献   

谈周朴园权势意识的凸现     

曾细珍 《衡水师专学报》2011,(2):50-51

《雷雨》是现代文学的经典之作,它含蓄的语言和丰富的潜台词是文坛上永不褪色的华彩。以周朴园的语言为分析对象,从语量和语势两角度,探析周朴园的权势意识的凸现手段,体会曹禺的语言艺术魅力。  相似文献   

试探"金陵十二钗"副册及又副册写了哪些人     

胥惠民 《新疆教育学院学报》2006,22(1):86-94

根据曹雪芹安排“金陵十二钗”正册顺序给我们的启发,加上脂砚斋的批语“宝玉系诸艳之贯”、“通部情案,皆必从石兄挂号”给我们的提示,即按照和贾宝玉的关系来确定是否进入“金陵十二钗”的名单,对副册、又副册名单作了具体的考索,希望能对理解《红楼梦》提供一定参考。  相似文献