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1.
Gerda Strutzenberger Tobias Wunsch Josef Kroell Jacqueline Dastl Hermann Schwameder 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):97-108
Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0–1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect. 相似文献
2.
格日乐图 《吉林体育学院学报》2005,21(1):46-47
揭示优秀速滑运动员蹬冰技术的时间特点，对明确clap式冰刀蹬冰技术动作结构具有重要的意义。通过运动学3维摄像方法分析后认为：在一个单步中右单步支撑时间大于左单步，而这种时值的延长体现在单支撑阶段。但右腿单支撑时间的延长并不是随意的，而是受节律限制，其单步时间与单支撑时间之比为：1．4：1。 相似文献
3.
为提高电动汽车能量利用率、改善车辆制动效果,依照制动踏板的不同工作状态,设计了一种并联制动控制策略。在制动踏板踩下的复合制动工况,按照相关制动法规对机械制动和再生制动进行合理分配;在滑行制动工况,以能量回收效率为目标函数,运用遗传算法优化电机在不同转速下的最佳制动转矩。分别在典型道路工况和常规制动工况下对该策略进行实车测试,结果表明:在中国轻型汽车行驶工况(CLTC-P)下,该策略的节能贡献度可达25.93%,在滑行制动工况能量回收效率较原车提升64.07%,车辆制动距离也有明显缩减。 相似文献
4.
对掷标枪最后用力技术的再认识 总被引：8，自引：0，他引：8
在分析和研究掷标枪最后用力技术的基础上，从掷标枪最后用力技术要求的本质出发，对一些有争议的技术环节提出看法，将最后用力技术分为5个阶段：右蹬技术、左蹬技术、“满弓”动作、“鞭打”动作、出手动作。 相似文献
5.
ABSTRACTHistorical pedal harps from the early nineteenth century are highly adorned objects, decorated with various techniques such as polychromy, gilding, decoupage, and gilt composition ornaments. Even though a large number of such instruments are kept in private and public collections, until now their decorative features have not been examined systematically. Moreover, little has been written about the motives behind the choice of various decorative techniques by harp makers. This article presents results from the investigation of a double-action harp made in 1818 by Erard, the leading manufacturer of harps in Regency London, focusing on the technological aspects of its decorative features. Various analytical methods, such as visual examination, microscopy, SEM-EDX, FTIR, and Py-GC-MS, were used to identify the inorganic and organic components in the coating of the harp and to analyse its stratigraphy. Inspection with ultraviolet light revealed details of the original layers and of later additions, while radiography made the internal structure as well as damaged areas and repairs visible. The outcome of this object-based examination was complemented by archival research on the Erard firm, providing new insight into Erard’s production and marketing strategies. 相似文献
6.
优秀跳远运动员起跳环节支撑腿表面肌电活动特征研究 总被引：2，自引：0，他引：2
通过表面肌电和运动学同步测试,揭示优秀跳远运动员起跳环节下肢肌肉表面肌电活动特征。研究结果表明：运动员起跳过程中比目鱼肌、腓肠肌、股外侧肌、股内侧肌是起跳腿的主要发力肌肉;所测肌肉最大发力时的顺序为：胫骨前肌首先发力,股外侧肌和股内侧肌次之,腓肠肌、比目鱼肌、股二头肌依次最后发力至最大;在整个起跳环节,踝关节和膝关节的拮抗肌共激活水平较高,其中尤以缓冲阶段踝关节的共激活水平最高。上述特征提示,在专项训练实践中,教练员应设计与跳远起跳用力特征相一致的专项力量训练手段,以打造出良好的专项力量素质。 相似文献
7.
Abstract The study investigated the absolute and relative (% maximal) physiological demands of constant power output at three pedal rates chosen to incorporate the range used by racing cyclists. Following the assessment of maximal exercise capabilities utilizing a recently developed racing cycle ergometry system, ten highly trained racing cyclists undertook a randomized sequence of work bouts at low (70.0 ± 1.1), medium (94.8 ± 0.8) and high (126.5 ± 1.1) pedal rates per minute at constant power output under an unloaded (free wheel) condition and under a loaded (196.2 ± 8.0 W) condition which demanded approximately 75% VO2 max. In both the unloaded and loaded conditions absolute cardiorespiratory demands of work at the highest pedal rate were significantly higher than those at the low and medium pedal rates (P<0.05). Similarly, the relative (% max) cardiorespiratory demands of unloaded work at the highest pedalling rate were significantly greater that at low and medium pedal rates (P < 0.05). There were clear, but nonsignificant trends of elevated relative cardiorespiratory demands during loaded work at the highest pedal rate, compared with low and medium pedal rates. Furthermore, net muscular efficiency demonstrated a significant decline (P<0.01) at the highest pedalling rate (21.2%) compared with the medium (24.0%) and low (25.6%) pedalling rates, confirming that metabolic economy of constant power output declined with increased pedalling rate under simulated racing cycling conditions. 相似文献
8.
伍建峰 《南昌教育学院学报》2012,(7):171+175
跳远踏板的准确性直接影响着运动员在比赛中个人水平的发挥,进而导致对比赛成绩产生不好的影响.即使是水平再高的运动员也会在比赛中因为种种原因而影响跳远踏板的准确性,所以,对于影响跳远踏板准确性的因素要深入地进行分析,以期在实践中帮助运动员针对性地规避内因等可控因素,同时也正确看待一些不可抗的外力因素对运动员产生的影响 相似文献
9.
孙大平 《贵阳学院学报(社会科学版)》2013,(1):97-100
钢琴被称为“乐器之王”,而踏板则被喻为“钢琴的灵魂”,由此可见踏板在钢琴演奏中的地位与作用。踏板在钢琴演奏中极具个性,不同的演奏家在同一乐曲的同一段落也许会运用不同的踏板技法,即便是同一个演奏家在不同场所演奏同一首乐曲,踏板的使用也可能会有变化。这种现象是许多因素所致,如乐器、声部平衡、作品风格、演奏场所和美学观等。踏板的准确运用可增强钢琴演奏的表现力,使乐曲更具生命力。 相似文献
10.
我国部分优秀女子沙滩排球运动员起跳环节肌电与运动学同步研究分析 总被引：1，自引：0，他引：1
林世行 《天津体育学院学报》2008,23(6):538-541
运用肌电与摄像对我国部分优秀女子沙滩排球运动员起跳环节的同步研究分析,结果表明:起跳时在一定范围内延长缓冲时间,有利于踩实沙子,减少蹬踏时的下陷幅度;缩短蹬伸时间,有利于下肢做爆发式的用力。踝关节、膝关节、髋关节运动方式符合能量传递原理,而各关节上附着的肌肉用力起始并不遵循动作顺序原理,主要是因沙地具有流动性、可压迫性造成的。这是沙排起跳用力方式与室内不同的主要特征之一。 相似文献