Timing of ball release in overarm throws affects ball speed in unskilled but not skilled individuals

We tested the hypothesis that variability in the timing of ball release in overarm throws affects ball speed. Nine unskilled and six skilled throwers made 30 throws fast and accurately from a sitting and standing position. Angular positions of finger and arm segments were recorded with search-coils at 1000 Hz; ball speed was measured with a radar gun. The time of ball release from the fingertips was measured with respect to seven arm kinematic reference points. Mean timing windows for ball release were 28 ms for unskilled throwers and 7 ms for skilled throwers. Mixed-model analyses of variance showed that a there was a statistically significant relationship between ball speed and the timing of ball release in unskilled throwers, but not in skilled throwers. This was presumably due to the difference in variability of the timing of ball release between the two groups. In contrast, skilled throwers showed a relationship between ball speed and peak forearm angular velocity (one measure of arm speed). We conclude that although variability in the timing of ball release can affect ball speed, this is only a major factor in unskilled throwers. When skilled throwers throw fast, variability in ball speed is due to variability in arm speed.     

Physiological correlates to off-road cycling performance

The aim of this study was to examine the relationships between maximal and submaximal tests for aerobic fitness and performance in an off-road cross-country circuit race. Thirteen competitive off-road male cyclists participated in the study. Peak oxygen uptake (VO2peak), peak power output, and lactate thresholds corresponding to 1 mmol x l(-1) above baseline (lactate threshold) and to 4 mmol x l(-1) (onset of blood lactate accumulation) were measured during an incremental cycling test. Race time and final ranking within the same group of cyclists were determined during a cross-country off-road competition. All correlations between the measured parameters of aerobic fitness and off-road cycling performance were significant, particularly between race time and physiological parameters scaled to body mass0.79 (r = -0.68 to -0.94; P < 0.05) and between final ranking and physiological parameters expressed relative to body mass0.79 (r = -0.81 to - 0.96; P < 0.001). Moreover, there was a large difference (effect sizes = 1.12-1.70) in all measured parameters of aerobic fitness between the group of six cyclists with a race time above the median and the group of six cyclists with a race time below the median (P < 0.05). In conclusion, the results of this study provide empirical support to the widespread use of these maximal (VO2peak, peak power output) and submaximal (lactate thresholds) parameters of aerobic fitness in the physiological assessments of off-road cyclists. Furthermore, our results suggest body size should be taken into account when evaluating such athletes.     

A single session of resistance exercise does not reduce postprandial lipaemia

This study investigated the effect of a single session of resistance exercise on postprandial lipaemia. Eleven healthy normolipidaemic men with a mean age of 23 (standard error = 1.4) years performed two trials at least 1 week apart in a counterbalanced randomized design. In each trial, participants consumed a test meal (1.2 g fat, 1.1 g carbohydrate, 0.2 g protein and 68 kJ x kg(-1) body mass) between 08.00 and 09.00 h following a 12 h fast. The afternoon before one trial, the participants performed an 88 min bout of resistance exercise. Before the other trial, the participants were inactive (control trial). Resistance exercise was performed using free weights and included four sets of 10 repetitions of each of 11 exercises. Sets were performed at 80% of 10-repetition maximum with a 2 min work and rest interval. Venous blood samples were obtained in the fasted state and at intervals for 6 h postprandially. Fasting plasma triacylglycerol (TAG) concentration did not differ significantly between control (1.03 +/- 0.13 mmol x l(-1)) and exercise (0.94 +/- 0.09 mmol x l(-1)) trials (mean +/- standard error). Similarly, the 6 h total area under the plasma TAG concentration versus time curve did not differ significantly between the control (9.84 +/- 1.40 mmol l(-1) x 6 h(-1)) and exercise (9.38 +/- 1.12 mmol x l(-1) x 6 h(-1)) trials. These findings suggest that a single session of resistance exercise does not reduce postprandial lipaemia.     

記憶研究的幾個問題

巴甫洛夫的研究、把注意放在条件反射联系形成,保持,和其表现的考查上,创造了牢固科学的基础,以理解在心理学中基本上获得识记,保持,和再生的过程,及其敍述的特征是什麽,并进一步作有效的研究。原则上巴甫洛夫学说,是和唯心主义的行为主义观念本质上不同的。巴甫洛夫     

拼球运动员要善于观察和判断临场情况

通常在谈排球比赛时,首先是谈队员通过球作出的各种动作.当排球比赛结束后,教练员只着重讲队员们所犯的技术性错误,却很少提到队员在接触球以前出现的错误动作.这是不对的.这样评价一场排球比赛是有很大局限性的.如果仔细分析一下队员的活动,你会确信,正是因为在接触球以前     

重寫人

一、重寫人和报紙的关系作为编輯部內部的工作者,他的許多工作公众很少知道,就是他的报館同事也很少知道。他是寫作工匠,对新聞有特别的了解,并且有可貴的采訪經驗。他是有經驗的記者有些記者在报館內工作比在街上采訪工作得好些。有些記者相反。一个人只要善于了解别人就能找到新聞重要來源的门徑了。可是,他們也許不会組織摘記,不会寫精彩的新聞。如果把他們采訪到的事     

400米跨栏运动员的力量训练

通过对高水平男女400米跨栏运动员的训练计划以及体育科学信息和个人经验的分析,我们得以了解到进行这一项目力量训练的一些有效途径.力量发展的年计划通常有两个主要阶段,第一阶段<11-12月份>是用来发展绝对力量和爆     

A comparison of time-motion performance between age groups in judo matches

The aim of this study was to compare time-motion indicators during judo matches performed by athletes from different age groups. The following age groups were analysed: Pre-Juvenile (13-14 years, n = 522), Juvenile (15-16 years, n = 353); Junior (19 years, n = 349) and Senior (>20 years, n = 587). The time-motion indicators included: Total Combat Time, Standing Combat Time, Displacement Without Contact, Gripping Time, Groundwork Combat Time and Pause Time. Analysis of variance (ANOVA) one-way and the Tukey test, as well as the Kruskal-Wallis test and Mann-Whitney (for non-parametric data), were conducted, using P < 0.05 as significance level. The results showed that all analysed groups obtained a median of 7 (first quantile - 3, third quantile - 12) sequences of combat/pause cycles. In total time of combat, the result was: for Total Combat Time, Standing Combat Time and Gripping Time: Pre-Juvenile and Senior were significantly longer than Juvenile and Junior. Considering Displacement Without Contact, Junior was significantly longer than all other age groups. For Groundwork Combat Time, Senior was significantly longer than all other age groups and Pre-Juvenile was longer than Junior. These results can be used to improve the physiological performance in intermittent practices, as well as technical-tactical training during judo sessions.