对散打运动员肢体打击效果的力学探讨     

王聚龙  李强 《广州体育学院学报》2004,24(4):27-29

采用献资料法并结合教学中的实践经验，分析了肢体打击效果的力学原理，提出了怎样加大散打肢体打击效果的一些力学方法和两条途径，给散打运动员提供力学的思维方式。  相似文献   

Option Strike Price and Managerial Investment Decisions     

刘鸿雁  张维 《天津大学学报(英文版)》2003,9(1)

Ｉｎｍｏｄｅｒｎｃｏｒｐｏｒａｔｉｏｎｓ ,ｔｈｅｂａｓｉｃｏｒｆｕｎｄａｍｅｎｔａｌｇｏａｌｓｏｆｂｏｔｈｔｈｅｐｒｉｎｃｉｐａｌ (ｏｒｓｔｏｃｋｈｏｌｄｅｒｓ)ａｎｄｔｈｅａ ｇｅｎｔ (ｏｒｔｈｅｍａｎａｇｅｒ)ａｒｅｔｏｍａｘｉｍｉｚｅｔｈｅｉｒｒｅｓｐｅｃｔｉｖｅｅｘｐｅｃｔｅｄｕｔｉｌｉｔｙ .Ｔｈｏｕｇｈ ,ｄｕｅｔｏｔｈｅｉｒｄｉｆｆｅｒｅｎｔｆｅａｔｕｒｅｓ ,ｔｈｅｙｍａｙｈａｖｅｑｕｉｔｅｄｉｆｆｅｒｅｎｔａｃｔｉｏｎｃｈｏｉｃｅｓ .Ｓｉｎｃｅｓｔｏｃｋ ｈｏｌｄｅｒｓ′ｉｎｖｅｓｔｍｅ…  相似文献   

Comparison of foot strike patterns of barefoot and minimally shod runners in a recreational road race     

《运动与健康科学(英文)》2014,3(2):137-142

BackgroundPrevious studies of foot strike patterns of distance runners in road races have typically found that the overwhelming majority of shod runners initially contact the ground on the rearfoot. However, none of these studies has attempted to quantify foot strike patterns of barefoot or minimally shod runners. This study classifies foot strike patterns of barefoot and minimally shod runners in a recreational road race.MethodsHigh-speed video footage was obtained of 169 barefoot and 42 minimally shod distance runners at the 2011 New York City Barefoot Run. Foot strike patterns were classified for each runner, and frequencies of forefoot, midfoot, and rearfoot striking were compared between the barefoot and minimally shod groups.ResultsA total of 59.2% of barefoot runners were forefoot strikers, 20.1% were midfoot strikers, and 20.7% were rearfoot strikers. For minimally shod runners, 33.3% were forefoot strikers, 19.1% were midfoot strikers, and 47.6% were rearfoot strikers. Foot strike distributions for barefoot and minimally shod runners were significantly different both from one another and from previously reported foot strike distributions of shod road racers.ConclusionFoot strike patterns differ between barefoot and minimally shod runners, with forefoot striking being more common, and rearfoot striking less common in the barefoot group.  相似文献   

Strike type variation among Tarahumara Indians in minimal sandals versus conventional running shoes     

《运动与健康科学(英文)》2014,3(2):86-94

PurposeThis study examined variation in foot strike types, lower extremity kinematics, and arch height and stiffness among Tarahumara Indians from the Sierra Tarahumara, Mexico.MethodsHigh speed video was used to study the kinematics of 23 individuals, 13 who habitually wear traditional minimal running sandals (huaraches), and 10 who habitually wear modern, conventional running shoes with elevated, cushioned heels and arch support. Measurements of foot shape and arch stiffness were taken on these individuals plus an additional sample of 12 individuals.ResultsMinimally shod Tarahumara exhibit much variation with 40% primarily using midfoot strikes, 30% primarily using forefoot strikes, and 30% primarily using rearfoot strikes. In contrast, 75% of the conventionally shod Tarahumara primarily used rearfoot strikes, and 25% primarily used midfoot strikes. Individuals who used forefoot or midfoot strikes landed with significantly more plantarflexed ankles, flexed knees, and flexed hips than runners who used rearfoot strikes. Foot measurements indicate that conventionally shod Tarahumara also have significantly less stiff arches than those wearing minimal shoes.ConclusionThese data reinforce earlier studies that there is variation among foot strike patterns among minimally shod runners, but also support the hypothesis that foot stiffness and important aspects of running form, including foot strike, differ between runners who grow up using minimal versus modern, conventional footwear.  相似文献   

试析1922年开滦五矿同盟罢工失败的主观原因   总被引：2，自引：0，他引：2  

阎永增  陈珺 《唐山师范学院学报》2004,26(1):69-71

1922年开滦五矿工人同盟大罢工，是中国第一次罢工高潮中最主要的一次罢工，在中国工运史上写下了光辉的一页，深入总结这次罢工失败的原因，尤其是主观原因，对全面认识这次罢工具有重要意义。文章对罢工失败的主观原因作了系统论述，并指出主客观因素的统一，应是全面考察这次罢工失败的立足点。  相似文献   

冷战后美国反恐怖主义政策评析     

纪胜利 《哈尔滨学院学报》2002,23(9):35-40

尽管冷战后美国的反恐怖主义措施比较全面有力，有许多值得借鉴之处，但是针对美国和国际社会的恐怖事件仍然层出不穷，说明美国的反思恐怖主义措施仍是治标不治本。要铲除恐怖主义必须标本兼治，国际社会要更加重视发展问题，公正地处理地区冲突，加强相互理解与对话，而不是刺激不同文明之间的对立。  相似文献   

长走向大断面顺槽连续快速掘进工艺研究     

鲁学斌 《雁北师范学院学报》2013,(3):74-76

文章介绍了机掘在走向长、断面大的顺槽中,通过选择适宜的支护形式、支护参数、支护材料以及支护质量,实现快速掘进的工艺流程,提升了掘进效率。  相似文献   

Three Strikes and You're Out     

《Legal Reference Services Quarterly》2013,32(4):55-85

Abstract

This research pathfinder is a comprehensive guide of the recent trend in criminal law for enhanced sentences for repeat offenders-pop-ularly called “three strike laws.” Particular attention is given to California law because it is the most often cited example of this type of law.  相似文献   

Comparison of plantar loads among runners with different strike patterns     

Zhen Wei  Zhiwang Zhang  Jiayi Jiang  Yu Zhang 《Journal of sports sciences》2013,31(18):2152-2158

ABSTRACT

This study aimed to explore the plantar loading variables between habitual rearfoot strike (RFS) and non-rearfoot strike (NRFS) during running. 78 healthy males participated in this study (41 RFS, 37 NRFS). In-shoe pressure sensors were used to measure plantar loading while the participants were running on a 15 m indoor runway with their preferred foot strike pattern (FSP) at 12.0 ± 5% km/h. Results indicate that force and pressure parameters were much higher in the rearfoot and midfoot regions during RFS running and relatively greater in forefoot region during NRFS running. However, compared with NRFS running, the contact area, maximum force and force-time-integrals during RFS running on total foot were 21.44% (P < 0.001, ES = 2.29), 13.99% (P = 0.006, ES = 0.64) and 21.27% (P < 0.001, ES = 0.85) higher, respectively. Total foot peak pressure and pressure-time-integral between two FSPs were similar. Higher loads in the rearfoot region may transmit to the knee joint and result in patellofemoral joint injuries. NRFS runners’ higher loads in forefoot seem to be ralated to metatarsal stress fractures and compensatory damage to the Achilles tendon. Therefore, runners should choose proper FSPs according to their unique physical conditions.  相似文献   

Lower extremity joint loads in habitual rearfoot and mid/forefoot strike runners with normal and shortened stride lengths     

Elizabeth R. Boyer  Timothy R. Derrick 《Journal of sports sciences》2018,36(5):499-505

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2–14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: ?9.9 ± 0.9, hFF-FFS: ?9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one’s SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads.  相似文献