Influence of a stressing constraint on stiffness and damping functions of a ski simulator's platform motion

The aim of this study was to assess the effect of stress on a previously acquired motor coordination. Following a longitudinal learning experiment, four participants performed oscillations on a ski simulator, either in normal or stressful conditions. The results showed that the amplitude of the oscillations decreased under stress, but no significant effect was seen regarding coordination, suggesting the strong resistance to stress of overlearned behaviour. Nevertheless, for one participant, a transient regression towards a former stage of learning was observed. This result was consistent with the regression hypothesis formulated by Fuchs (1962).     

String vibration dampers do not reduce racket frame vibration transfer to the forearm

In this study, we examined the effect of string vibration damping devices on reducing racket frame vibration transfer to the forearm. Twenty participants volunteered to hold a tennis racket stationary in a forehand and backhand stroking position while tennis balls were fired at 20 m x s(-1) towards two impact locations, the node of vibration and the dead spot. A three-way analysis of variance with repeated measures on damping condition, impact location and stroke condition was performed on the data. The resonant frequency of the hand-held racket was found to be approximately 120 Hz. No significant differences in amplitude of vibration at the resonant frequency were found for the wrist or the elbow when damped and non-damped impacts were compared. Impacts at the dead spot produced greater amplitudes of vibration (P < 0.01) but no interaction between impact location and string dampers was evident. The string dampers had no effect on the grip force used or the muscle electrical activity in the forearm after impact. In conclusion, we found that string dampers do not reduce the amount of racket frame vibration received at the forearm. We suggest that string dampers remain a popular accessory among tennis players because of their acoustic effects and psychological support rather than any mechanical advantage.     

从手球比赛中运动员受罚情况分析防守上存在的问题

通过对国内外一些重大手球比赛的情况分析，阐述在日常训练中，各级教练员要正确处理好防与攻的关系，加强提高一防一的对抗能力，从而使手球运动的技、战术更向前推进一步。     

Effect of verbal instructions and image size on visual search strategies in basketball free throw shooting

We assessed the effects on basketball free throw performance of two types of verbal directions with an external attentional focus. Novices (n = 16) were pre-tested on free throw performance and assigned to two groups of similar ability (n = 8 in each). Both groups received verbal instructions with an external focus on either movement dynamics (movement form) or movement effects (e.g. ball trajectory relative to basket). The participants also observed a skilled model performing the task on either a small or large screen monitor, to ascertain the effects of visual presentation mode on task performance. After observation of six videotaped trials, all participants were given a post-test. Visual search patterns were monitored during observation and cross-referenced with performance on the pre- and post-test. Group effects were noted for verbal instructions and image size on visual search strategies and free throw performance. The 'movement effects' group saw a significant improvement in outcome scores between the pre-test and post-test. These results supported evidence that this group spent more viewing time on information outside the body than the 'movement dynamics' group. Image size affected both groups equally with more fixations of shorter duration when viewing the small screen. The results support the benefits of instructions when observing a model with an external focus on movement effects, not dynamics.     

Change in throwing pattern: critical values for control parameter of velocity

The purpose of this study was to determine the critical values at which throwing patterns change when scaling up on the control parameter of velocity. Thirty-six participants (ages: 6-12 years) were categorized into four throwing levels according to patterns represented by temporal joint lag. Each participant was required to complete 5 overhand throws at each of 10 relative velocities for a total of 50 trials per participant. The lowest velocity was 10% of maximum, with increases in increments of 10% up to a maximum effort. Quantitative and qualitative analyses indicated that critical values varied according to throwing category and joint. Generally, lower skilled throwers (Levels 1 and 2) had less stable joint lag and changed patterns at lower velocities than higher skilled (Levels 3 and 4) throwers.     

“老虎”伍兹成功的内幕

在“虎”爸的眼中,印度民族英雄甘地、南非前总统曼德拉远不如他的儿子“老虎”伍兹。这位狂傲的老先生认为自己的儿子是“上帝选中的人”,是“下一个救世主”。“老虎”伍兹现在是高尔夫球坛最有天赋和财富的球员,而他的爸爸埃尔·伍兹,已经把“老虎”出生的房子设定为将来的高尔夫圣地。“虎穴”将成圣地在“老虎”伍兹功成名就后,“虎”爸埃尔并没有搬到一些更名贵的住宅区,而是仍住在当年儿子成长的那间屋子里,因为埃尔深信这间房子终有一天会成为全美国高尔夫球爱好者朝拜的圣地,所以他要守住这块宝地。     

The effect of two different 18-week walking programmes on aerobic fitness, selected blood lipids and factor XIIa

Forty-nine previously sedentary or low active individuals aged 40-71 years were allocated to three groups. The long walking group participated in an 18-week walking programme which consisted of walks lasting 20-40 min; the repetitive short walking group completed walks of between 10 and 15 min, up to three times a day, with no less than 120 min between each walk; and the control group maintained their low level of activity. Both walking programmes began at a prescribed 60 min x week(-1), which increased steadily up to 200 min x week(-1) by week 12. During the study, the long walking group walked for an estimated 2514 min (139 min x week(-1)), expending an estimated 67.5 MJ (3.72 MJ x week(-1)) at an estimated 73% of their age-predicted maximum heart rate and 68% of their estimated VO2max. The repetitive short walking group walked for an estimated 2476 min (135 min x week(-1)), expending an estimated 58.5 MJ (3.17 MJ x week(-1)) at an estimated 71% of their age-predicted maximum heart rate and 65% of their estimated VO2max. The results showed a statistically significant reduction in heart rate during a standardized step test (pre- vs post-intervention) in both walking groups, indicating an improvement in aerobic fitness, although the control group showed a higher average heart rate during the post-intervention test, indicating reduced fitness. When compared with the male subjects pre-intervention, the females possessed more favourable levels of high-density lipoprotein (HDL) cholesterol (P< 0.001), apolipoprotein (apo) AI (P < 0.001) and ratios of total cholesterol:HDL cholesterol (P< 0.02) and low-density lipoprotein (LDL) cholesterol: HDL cholesterol (P< 0.02). Compared with the controls post-intervention, the walking groups showed no statistically significant changes in total cholesterol, LDL cholesterol, HDL cholesterol, apo AI, apo AII, apo B, or the ratios of total cholesterol: HDL cholesterol, LDL cholesterol: HDL cholesterol, apo AI: apo B or apo AI: apo AII (P > 0.05). Relative to the walking groups, factor XIIa increased in the control group (P < 0.05). We conclude that, although both walking programmes appeared to improve aerobic fitness, there was no evidence of improvements in the blood lipids or associated apolipoproteins of the walking groups. Further analysis indicated that this apparent lack of change may have been related to the subjects' relatively good pre-intervention blood lipid profiles, which restricted the potential for change. The implications of the observed changes in the coagulation/fibrinolytic factors remain unclear.     

大腕

曼联又赢了!从2001年12月15日的英超第17轮对米德尔斯堡开始,他们接连取得了8连胜(包括2002年1月7日的足总杯比赛),这些接连不断的胜利使得这支昔日的无敌之师又一次攀升到了联赛积分榜首席,尽管只是以净胜球的优势暂居第一的位置,但是对于厚爱“红魔”的球迷来说不啻于天大的惊喜,要知道一个多月以前他     

疾速60秒

一身休闲的运动装,还有一张青春的面庞,走在大街上如果你看到史青玉的模样,你会认为他与时下很标准的时尚青年没有区别,甚至当他坐在我面前的时候,我都难以相信他就是本届亚运会场地自行车个人赛的第五名。他太年轻了,看起来就像刚上大学的年轻人,可就是他,在本届亚运会上拼尽全力为我国在不是优势项目上挣得了足够的荣誉,也为黑龙江省自行车队闯出了名声。 今年只有21岁的史青玉出生在1981年,由于从小就接受体育锻炼,所以他的身体素质非常好,也许正是这无心插柳的结果使他走上了自行车的道路,1998年的时候他从齐齐哈尔业余体校来到哈尔滨试训,他强壮的身体和良好的柔韧性给教练留下了深刻的印象,于是当教练征求他的意见愿不愿意从事自行车运动时,年轻的史青玉毫不犹豫地答应了。哪个时候太小了,什么也不懂,丝毫没有考虑到训练的艰苦,现在再想,自行车是世界上最艰苦的运动,而且非常地枯燥,训练起来非常地累,一天下来什么