Effects of adding a preceding run-up on performance, blood lactate concentration and heart rate during maximal intermittent vertical jumping

In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps.     

Characterizing the mechanical parameters of forward and backward falls as experienced in snowboarding

Wrist injuries are frequently observed after falls in snowboarding. In this study, laboratory experiments mimicking forward and backward falls were analysed. In six different falling scenarios, participants self-initiated falls from a static initial position. Eighteen volunteers conducted a total of 741 trials. Measurements were taken for basic parameters describing the kinematics as well as the biomechanical loading during impact, such as impact force, impact acceleration, and velocity. The effective mass affecting the wrist in a fall also was determined. The elbow angle at impact showed a more extended arm in backward falls compared to forward falls, whereas the wrist angle at impact remained similar in forward and backward falls. The study results suggest a new performance standard for wrist guards, indicating the following parameters to characterize an impact: an effective mass acting on one wrist of 3-5 kg, an impact angle of 75 degrees of the forearm relative to the ground, and an impact velocity of 3 m/s.     

Effect of a semi electro-mechanical engine valve on performance and emissions in a single cylinder spark ignited engine

In this study, an electro-mechanical valve （EMV） system for the intake valve ofa fottr stroke, single cylinder, overhead valve and spark ignition （SI） engine was designed and constructed. An engine with the EMV system and a standard engine were tested to observe the effects of the EMV on engine performance and emissions at different speeds under full load. The EMV engine showed improved engine power, engine torque and break specific fuel consumption （BSFC）. A 66% decrease in CO emissions was also obtained with the EMV system, but hydrocarbons （HC） and NOx emissions increased by 12% and 13% respectively.     

英国联合信息系统委员会2010—2012年战略规划（草案）

1外界环境 自JISC的上一份发展战略实施以来,教育环境已经发生了重大变化。技术上的巨大发展、特别是网络技术的发展非常迅速,近期英国及世界经济出现越来越多的危机和严重的滑坡,这些变化使得JISC在考虑如何为其团体提高自身附加值具有极其重要的意义。     

快意复活节岛:失落于世界尽头的静美

"他们中有的刻有文身,有的胖,有的瘦,我们觉得可以根据他们鼻子的特点辨别出镇上一些人之间的关系",帕特里夏·瓦尔加斯说道。我现在身处复活岛。帕特里夏是一位考古学家,也是智利的建筑旅游服务组织(ATS)的创始人之一。她正在介绍"摩艾"这举世闻名的巨石群,这些石像是在公元12至14世纪由岛上新石器时代的住民在山上开凿而成。     

“阿尔茨海默”的宽恕

2010年2月,那个我人生中所知的"父亲"去世了,那时候我见过母亲。去年8月我再去纽约上州探望母亲,我觉得那应当是她最后一次认出我了。两年半的时间没见面,母亲的病情明显恶化了。     

我按爷爷的方式生活

我的爷爷是个与众不同的人。他第一次带我去钓鱼时,我才发现他是多么的与众不同。那是一个夏天,我们沿着山岗的斜坡,去往他的秘密钓鱼塘。爷爷沿着只有他那双老练的眼睛才能辨出的山间小路迂回前进,一路上说个不停。他熟知他农场中的每一块石头和每一棵植物。我艰难地往前赶才能跟上他那大步流星的脚步,听清他滔滔不绝的话语。“没多远了,”爷爷拨开树枝向我喊道。我们在一对对高大的松树中间蜿蜒穿行。到处都是松树的针叶。我们就像置身于一条隧道之中。一条漆黑的隧道。最后,我们终于穿过了松林,站在一潭犹如清晨一样清爽袭人的池塘边。“…     

THE GIFT OF THE MAGI

漂亮的发卡倾诉着爱的浪漫,精致的表链承载着爱人的良苦用心。这一切正是因为爱着你的爱,梦着你的梦,所以快乐着你的快乐,幸福着你的幸福。