Coordination variability and skill development in expert triple jumpers

The aim of this study was to examine the influence of skill of expert triple jumpers on the coordination variability of lower extremity intra-limb couplings. In contrast to the traditional motor learning perspective, we hypothesized that as skill and thus performance increases, movement coordination variability will also increase. Three-dimensional kinematic and ground reaction force data were collected during the hop-step transition phase of the triple jump. Relative motion plots and a modified vector coding technique were used to quantify the coordination variability across the trials. The results were consistent with a U-shaped curve, representing coordination variability, as skill increases. The high coordination variability in less skilled athletes is present while the appropriate characteristics defining the movement coordination patterns are acquired. This coordination variability may not be beneficial to performance. As the refinement of these characteristics is achieved, coordination variability decreases, resulting in a more consistent or regulated performance. In the final stages of developing a skilled performance, a functional variability is accessed that brings flexibility to the system allowing it to cope with perturbations. This study highlights the need to address the learning effect when analysing coordination variability from a dynamical systems perspective.     

迷上练习场

在许多职业赛事上,你不用破费很多就可以大有所获。乔·狄克逊的下巴紧紧贴在球场的钢丝网上,场内的罗杰·费德勒现在离她只有不到5码远。这位她最喜爱的网球选手,在她的注视下练习完上旋发球后,接着开始练习正手抽击。这是一记典型的费德勒式正拍,球"嗖"地飞出,刚刚过网,狠狠地砸在了边线上。狄克逊情不自禁地吹了个口哨,费德勒轻     

巴黎风情画——Blizzard WWI 2008赛场日记

很荣幸参加2008 Blizzard Enter- tainment Worldwide Invitational,作为WE魔兽世界竞技场战队的成员。第一次参加《魔兽世界:燃烧的远征》(World of WarCraft:The Burning Crusade)的竞技场大赛,虽然最后没能取得理想的成绩,但从魔兽世界目前极少的线下赛来看,WWI确实是一次难得的锻炼机会,这次失败也促使我更加努力的练习,对胜利的渴望,遗憾绝对不会留到下次!     

浅谈初级DotA CW阵容与节奏的掌握

DotA游戏基本可以分为以下几个层次：单机AI、路人战、IH、CW比赛。当你厌倦了每天在路人房里孤军备战,而有时队友又让你无奈。或许会找到一个小团体进行IH、内战、开黑,而开黑时往往双方实力悬殊,不能良好地发挥个人实力,基本会养成一些路人战的坏习惯。这时找一个大的平台,进行CW吧!这更正式、更有竞技性,双方都有很强实力的比赛是非常精彩的。其中在IH以后就要考虑阵容问题了,而高等CW还要考虑相互克制关系,团战破解对方优势的打法,这里主要谈一下目前较热的初级CW的一些细节。     

《电子竞技》专访：走近波兰战神NEO

今天《电子竞技》特约记者N.n为大家带来一个neo的独家采访。采访的过程其实是一波三折的,早在一个月前我们打算为这位憨态可掬的战神小朋友（呃,憨态可掬,原谅我用了这个词,暂时没有想到别的形容他可爱的词）做一个特别专访。     

Mixing methods in assessing coaches' decision making

Mixing methods has recently achieved respectability as an appropriate approach to research design, offering a variety of advantages (Tashakkori & Teddlie, 2003). The purpose of this paper is to outline and evaluate a mixed methods approach within the domain of coaches' decision making. Illustrated with data from a policy-capturing study on coaches' decisions about an injured gymnast's participation in competition, the approach involves the concurrent collection of quantitative and qualitative data and a three-phase process of data analysis. It is argued that (a) the method described can provide additional insights into the factors involved in coaches' decision making, beyond those provided via quantitative or qualitative methods alone, and (b) mixing methods holds promise for coaching research more generally.     

The influence of self-determination in physical education on leisure-time physical activity behavior

Using a multitheory approach, this study was designed to investigate the influence of urban adolescents' perceived autonomy and competence in physical education on their physical activity intentions and behaviors during leisure time. A transcontextual model was hypothesized and tested. Urban adolescents (N=653, ages 11-15 years) completed questionnaires assessing relevant psychological constructs and moderate to vigorous physical activity and then had their cardiorespiratory fitness assessed with the Progressive Aerobic Cardiovascular Endurance Run (PACER) test. Based on our structural equation modeling analyses and fit indexes, the transcontextual model adequately fit the data. We concluded that the two theoretical frameworks--SDT and theory of planned behavior--can be integrated to provide an enhanced understanding of the influence of physical education on leisure-time physical activity. The results revealed that perceived autonomy and competence in physical education are interrelated and function as a whole for enhancing leisure-time physically active intentions and behavior.     

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 - 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g x kg(-1) body mass x day(-1); n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.     

Effects of rest interval during high-repetition resistance training on strength, aerobic fitness, and repeated-sprint ability

The effect of altering the rest period on adaptations to high-repetition resistance training is not well known. Eighteen active females were matched according to leg strength and repeated-sprint ability and randomly allocated to one of two groups. One group performed resistance training with 20-s rest intervals between sets, while the other group employed 80-s rest intervals between sets. Both groups performed the same total training volume and load. Each group trained 3 days a week for 5 weeks [15- to 20-repetition maximum (RM), 2 - 5 sets]. Repeated-sprint ability (5x6-s maximal cycle sprints), 3-RM leg press strength, and anthropometry were determined before and after each training programme. There was a greater improvement in repeated-sprint ability after training with 20-s rest intervals (12.5%) than after training with 80-s rest intervals (5.4%) (P = 0.030). In contrast, there were greater improvements in strength after training with 80-s rest intervals (45.9%) than after training with 20-s rest intervals (19.6%) (P = 0.010). There were no changes in anthropometry for either group following training. These results suggest that when training volume and load are matched, despite a smaller increase in strength, 5 weeks of training with short rest periods results in greater improvements in repeated-sprint ability than the same training with long rest periods.