EMG amplitude and spatial assimilation effects in rapid bimanual movement.

To investigate whether spatial assimilation effects are due to premovement control processes or postinitiation feedback processes, surface EMG recordings were made from two agonists and one antagonist during both single and dual movements involving the upper limb(s). In the single condition, subjects (N = 7) made 25 Short (20 degrees) and 25 Long (60 degrees) reversal movements using levers in the sagittal plane, in 195 ms to reversal. In the dual condition, both Short and Long movements were performed simultaneously for 75 trials, the last 25 of which were without knowledge of results. Subjects overshot the Short target in the dual condition, showing spatial assimilation effects. Overshooting was associated with increased peak EMG in the initial (premovement) agonist burst, supporting the notion that spatial assimilation effects are modulated via premovement control processes.     

Spatial assimilation effects and error detection in rapid overlapping and sequential bimanual movements.

This study verified earlier anecdotal evidence indicating that spatial assimilations could be reduced by offsetting movements in time. In Experiment 1, 40 right-handed participants (ages 18-23 years) made single and dual quick lever reversals of 20 degrees and 60 degrees with the left and right limbs, respectively. Participants were assigned to either the Overlapping (O) group, in which one limb began when the other limb reached the reversal point, or to the Sequential (S) group in which one limb followed the other with a delay of 114 ms, on average. The shorter-distance limb of the O group overshot relative to the S group. Short-distance spatial assimilations were also shown in the S group in Experiment 2, when the delay was increased to 250, 500, or 1,500 ms (N = 30), suggesting that assimilation effects can be caused by command interactions at both the planning and the execution levels.     

Divided attention in bimanual aiming movements: effects on movement accuracy

The role of focusing attention on one limb or both limbs in a bimanual aiming task was investigated in two experiments. Participants were prompted to focus attention on either limb (Experiment 1) or were free to choose their attentional strategy (Experiment 2). Fifty-two college-aged participants made quick, bimanual lever reversals in the sagittal plane over 20 degrees and 60 degrees in 210 ms to the reversal point. In both experiments, spatial accuracy was better when participants focused their attention on a single limb compared to the nonattended limb and when they paid attention to both limbs. However, no differences were shown on a no-knowledge of results (KR) retention test when participants paid attention to both limbs. In the second experiment, differences were maintained on a no-KR retention test when participants continued to select their own attentional strategy, although the statistical effect was smaller than in the first experiment. The findings suggested that the movement parameter selection process benefited from attentional focus.     

Detecting and correcting errors in rapid aiming movements: effects of movement time, distance, and velocity

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal that serves as a basis for a correction. The main question addressed in the current study was how distance, movement time, and velocity influence both spatial or temporal error detection. Forty college-aged participants (30 women and 10 men) performed rapid aiming movements over 30 degrees or 50 degrees in either 210 ms or 350 ms without vision. The participants verbally estimated the distance moved and the movement time during acquisition before knowledge of results was given and during an immediate retention test without knowledge of results. Spatial and temporal objective-subjective correlations were greater in the 210-ms condition compared to the 350-ms condition, but were not related to movement velocity.     

Random and blocked practice of movement sequences: differential effects on response structure and movement speed

Three similar six-element key press sequences were practiced under blocked or random practice schedules with acquisition conducted on one day and retention and transfer on the next day. The task required participants to type, as quickly as possible, one of three 6-element sequences as observed on a computer monitor. In blocked practice, participants completed all practice in one repeated sequence before the next repeated sequence was introduced. In random acquisition practice, the three repeated sequences were randomly presented to the participants. The data suggest that random practice results in participants adopting a uniform response structure, while blocked practice allows participants to exploit unique sequential aspects of the individual tasks. This finding suggests that random practice may not be as effective as blocked practice when one of the tasks being practiced together can be optimized through the development of a unique response structure.     

The end-state comfort effect in bimanual grip selection

During a unimanual grip selection task in which people pick up a lightweight dowel and place one end against targets at variable heights, the choice of hand grip (overhand vs. underhand) typically depends on the perception of how comfortable the arm will be at the end of the movement: an end-state comfort effect. The two experiments reported here extend this work to bimanual tasks. In each experiment, 26 right-handed participants used their left and right hands to simultaneously pick up two wooden dowels and place either the right or left end against a series of 14 targets ranging from 14 to 210 cm above the floor. These tasks were performed in systematic ascending and descending orders in Experiment 1 and in random order in Expiment 2. Results were generally consistent with predictions of end-state comfort in that, for the extreme highest and lowest targets, participants tended to select opposite grips with each hand. Taken together, our findings are consistent with the concept of constraint hierarchies within a posture-based motion-planning model.     

Retroactive interference effects of mentally imagined movement speed

In two retroactive interference experiments, we assessed the effect of mentally imagined movement speed on subsequent motor performance. All participants performed a sequential motor action at three speeds during a baseline test and a retention test. During the retention interval of Experiment 1, the participants (n = 50) physically performed the action at a slow speed, physically performed it at a fast speed, imagined it at a slow speed, imagined it at a fast speed, or performed a no-practice control task. In Experiment 2, the participants (n = 24) imagined the movement, overtly vocalized words, or both, all at a slow speed. The results revealed that the speed of the imagined motor action affected the speed of subsequent performance in the retention test and that imagery and physical practice were functionally equivalent. The results are consistent with Lang's bio-informational theory.     

Retroactive interference effects of mentally imagined movement speed

In two retroactive interference experiments, we assessed the effect of mentally imagined movement speed on subsequent motor performance. All participants performed a sequential motor action at three speeds during a baseline test and a retention test. During the retention interval of Experiment 1, the participants (n = 50) physically performed the action at a slow speed, physically performed it at a fast speed, imagined it at a slow speed, imagined it at a fast speed, or performed a no-practice control task. In Experiment 2, the participants (n = 24) imagined the movement, overtly vocalized words, or both, all at a slow speed. The results revealed that the speed of the imagined motor action affected the speed of subsequent performance in the retention test and that imagery and physical practice were functionally equivalent. The results are consistent with Lang's bio-informational theory.     

The effects of stride technique and pitch location on slo-pitch batting

In slo-pitch softball, the ball is delivered in an arc trajectory with a moderate velocity; hence, batters have time to adjust their stride technique based on the pitched ball location. The purpose of this study was to examine the influence of stride technique and pitched ball location on the mechanics of slo-pitch batting. A two-way ANOVA of two locations of pitch (inside and outside) x three strides (open, parallel, and closed) repeated measure study was conducted in this study. The results showed that the stride technique and pitched ball location did not have a consistent impact on the participants across different batting conditions, so the study recommends slo-pitch batters to explore different stride techniques when striking the ball. Further, to better understand the generalizability of the findings, the results indicated that participants were quite homogeneous as a group. Hence, coaches and educators may apply the findings from this study to other players with similar skill level.     

审美中的距离与参与

距离与参与问题是美学研究的热点和焦点问题之一。“距离”棍念具有多义性，既可指空间距离、时间距离，又可指艺术与生活之间的距离，更重要的指心理距离、审美距离。“距离”说的背后隐藏着明显的二元思维模式和鲜明的精英化立场。“距离”与“参与”相对，但“距离”本不拒绝“参与”。“距离”也罢，“参与”也罢，都有个“度”的问题，它们只是审美活动的不同侧面、不同维度、不同阶段而巳，不能只强调一方而无视另一方的存在。     

Psychological effects of rapid weight loss and attitudes towards eating among professional jockeys

Abstract

We examined the psychological effects of rapid weight loss among a sample of 41 professional jockeys (mean age 30.9 years, s = 7.0). Participants completed the Brunel Mood Scale (BRUMS) and the Eating Attitudes Test-26 (EAT-26) to establish the relationships between rapid weight loss, mood, and attitudes towards eating. These instruments were administered on three occasions: at the jockeys' minimal weight (achieved through rapid weight loss), their optimal riding weight (when they were not excessively restricting their weight and felt healthy), and their relaxed weight (when there were no forthcoming light rides or no rides at all). It was hypothesized that when riding at minimal weight, jockeys would record a more negative mood profile compared with scores recorded at optimal or relaxed weights. The same trend was expected for eating attitudes. These hypotheses were supported as jockeys reported significantly more negative mood profiles and eating attitudes at minimal weight. The EAT-26 scores indicated the presence of disordered attitudes towards eating at this weight. These results suggest that jockeys' endeavours to reach the minimum weight limit stipulated by governing bodies are likely to jeopardize their psychological well-being. Dialogue surrounding the appropriateness of current weight regulations is therefore encouraged.     

Psychological effects of rapid weight loss and attitudes towards eating among professional jockeys

We examined the psychological effects of rapid weight loss among a sample of 41 professional jockeys (mean age 30.9 years, s = 7.0). Participants completed the Brunel Mood Scale (BRUMS) and the Eating Attitudes Test-26 (EAT-26) to establish the relationships between rapid weight loss, mood, and attitudes towards eating. These instruments were administered on three occasions: at the jockeys' minimal weight (achieved through rapid weight loss), their optimal riding weight (when they were not excessively restricting their weight and felt healthy), and their relaxed weight (when there were no forthcoming light rides or no rides at all). It was hypothesized that when riding at minimal weight, jockeys would record a more negative mood profile compared with scores recorded at optimal or relaxed weights. The same trend was expected for eating attitudes. These hypotheses were supported as jockeys reported significantly more negative mood profiles and eating attitudes at minimal weight. The EAT-26 scores indicated the presence of disordered attitudes towards eating at this weight. These results suggest that jockeys' endeavours to reach the minimum weight limit stipulated by governing bodies are likely to jeopardize their psychological well-being. Dialogue surrounding the appropriateness of current weight regulations is therefore encouraged.     

对“功能动作训练”之“功能动作筛查”的审视与思考

作为一种全新训练理念的代表——功能动作训练正逐渐被我国专家学者及教练员所接受.所谓“功能动作训练”是在对人体基本动作模式进行测试、诊断和纠正的基础上,采用某些特殊设计的动作练习手段,以最大限度地规避运动损伤风险,提高动作效率,促进运动水平提高的动作方法体系的总和.其核心内容包括功能动作筛查、伤病预防和动作准备等8个部分.作为整个功能动作训练体系的奠基石,功能动作筛查的重要性是不言而喻的.分别从原理、作用、操作、排序及纠正方法5个方面对功能动作筛查理论进行系统的研究,以期为后续研究功能动作训练体系其他方面的内容奠定基础.     

Game location and aggression in rugby league

The present study examined the relationship between aggression and game location in rugby league. We videotaped a random sample of 21 professional rugby league games played in the 2000 Super League season. Trained observers recorded the frequency of aggressive behaviours. Consistent with previous research, which used territoriality theories as a basis for prediction, we hypothesized that the home team would behave more aggressively than the away team. The results showed no significant difference in the frequency of aggressive behaviours exhibited by the home and away teams. However, the away teams engaged in substantially more aggressive behaviours in games they lost compared with games they won. No significant differences in the pattern of aggressive behaviours for home and away teams emerged as a function of game time (i.e. first or second half) or game situation (i.e. when teams were winning, losing or drawing). The findings suggest that while home and away teams do not display different levels of aggression, the cost of behaving aggressively (in terms of game outcome) may be greater for the away team.     

Game location and aggression in rugby league

The present study examined the relationship between aggression and game location in rugby league. We videotaped a random sample of 21 professional rugby league games played in the 2000 Super League season. Trained observers recorded the frequency of aggressive behaviours. Consistent with previous research, which used territoriality theories as a basis for prediction, we hypothesized that the home team would behave more aggressively than the away team. The results showed no significant difference in the frequency of aggressive behaviours exhibited by the home and away teams. However, the away teams engaged in substantially more aggressive behaviours in games they lost compared with games they won. No significant differences in the pattern of aggressive behaviours for home and away teams emerged as a function of game time (i.e. first or second half) or game situation (i.e. when teams were winning, losing or drawing). The findings suggest that while home and away teams do not display different levels of aggression, the cost of behaving aggressively (in terms of game outcome) may be greater for the away team.     

奥林匹克运动与经济

奥林匹克运动与经济有着内在的必然的联系，离开物质基础和经济实力，奥林匹克就无法生存和发展。但奥林匹克运动毕竟不是经济活动，奥林匹克在与经济结合时，有自己的宗旨、特征和运动方式，在北京申办2008年奥运会成功后，深刻认识和分析奥林匹克运动与经济的关系，有助于我们趋利避害，推动奥林匹克运动的普及和发展。     

中长跑

技术概述与短跑运动员以脚前掌外侧着地不同,中跑运动员更倾向于用脚的中部外侧着地,而长跑运动员则以脚的中部与脚跟之间的外侧着地。在中、长跑中,脚的着地过程都是由脚尖移至整个脚掌,进而由于体重因素,脚跟触地。