Automatic measurement of key ski jumping phases and temporal events with a wearable system   总被引：1，自引：0，他引：1  

Chardonnens J  Favre J  Le Callennec B  Cuendet F  Gremion G  Aminian K 《Journal of sports sciences》2012,30(1):53-61

We propose a new method, based on inertial sensors, to automatically measure at high frequency the durations of the main phases of ski jumping (i.e. take-off release, take-off, and early flight). The kinematics of the ski jumping movement were recorded by four inertial sensors, attached to the thigh and shank of junior athletes, for 40 jumps performed during indoor conditions and 36 jumps in field conditions. An algorithm was designed to detect temporal events from the recorded signals and to estimate the duration of each phase. These durations were evaluated against a reference camera-based motion capture system and by trainers conducting video observations. The precision for the take-off release and take-off durations (indoor < 39 ms, outdoor = 27 ms) can be considered technically valid for performance assessment. The errors for early flight duration (indoor = 22 ms, outdoor = 119 ms) were comparable to the trainers' variability and should be interpreted with caution. No significant changes in the error were noted between indoor and outdoor conditions, and individual jumping technique did not influence the error of take-off release and take-off. Therefore, the proposed system can provide valuable information for performance evaluation of ski jumpers during training sessions.  相似文献   

The planarity of the stickface motion in the field hockey hit     

Willmott AP  Dapena J 《Journal of sports sciences》2012,30(4):369-377

The field hockey hit is an important but poorly understood stroke. In this study, we investigated the planarity of the stickface motion during the downswing to better characterize the kinematics and to assess the suitability of planar pendulum models for simulating the hit. Thirteen experienced female field hockey players were filmed executing hits with a single approach step, and the kinematics of the centre of the stickface were measured. A method was developed for identifying how far back from impact the stickface motion was planar. Orthogonal regression was used to fit least-squares planes to the stickface path during sections of the downswing of varying length, with each section ending at impact. A section was considered planar if the root mean square residual between the stickface path and the fitted plane was less than 0.25% of the distance travelled by the stickface during that period. On average, the stickface motion was planar for the last 83 ± 12% of its downswing path, with the length of the planar section ranging from 1.85 m to 2.70 m. The suitability of a planar model for the stickface motion was supported, but further investigation of the stick and arm kinematics is warranted.  相似文献   

Achieving optimum sports performance during Ramadan: some practical recommendations     

RJ Maughan  Y Zerguini  H Chalabi  J Dvorak 《Journal of sports sciences》2012,30(Z1):S109-S117

Muslim athletes should fast from sunrise to sunset each day throughout the 30 days of Ramadan. Most athletes will continue to train throughout Ramadan, and they may also be required to compete at this time, but they will also engage in the religious, cultural, and social activities that Ramadan represents. The available evidence indicates that high-level athletes can maintain performance during Ramadan if physical training, food and fluid intake, and sleep are appropriate and well controlled. Individualized monitoring of athletes may help to prevent fatigue and overtraining and to reduce the risk of consequent illness and injury. The timing and intensity of training may require adjustment to optimize the training response, and training close to or after sunset may have advantages, but this will vary between individual and team sports and between environments that are predominantly Muslim and those that are predominantly non-Muslim. Training late in the day allows nutrition interventions after training to promote adaptations to the training stimulus, to promote recovery, and might help to reduce muscle damage. Sleep deficits have a number of adverse effects on well-being and performance, and athletes should ensure adequate sleep throughout Ramadan. In non-Muslim majority environments, especially in team sports, coaches and athletes should be sensitive to the needs of their team-mates who may be fasting. Event organizers should take account of the needs of Muslim athletes when scheduling the dates and timings of sports competitions.  相似文献   

Enlightenment and measurement - a way to improve health among high school students     

J Greve  LB Andersen 《Journal of sports sciences》2012,30(12):1199-1205

Abstract This paper examines the effect of participating in a web-based health programme that promotes personal tracking of high school students' own measurements of a number of health-related parameters. Danish cross-sectional survey data were used to examine the effects of the health programme on various health measures. Both quantile regression models and standard ordinary least squares (OLS) models were used to explore the correlations between the students' participation in the health programme and their body mass index (BMI), body fat percentage, aerobic fitness, and well-being. Participation in the health programme increased BMI and aerobic fitness among students with a BMI or an aerobic fitness value ranging from the 25th percentile to the 75th percentile and reduced body fat percentage among students with the highest percentages of body fat. In addition, the health programme led to an increased feeling of wellbeing among students, especially those with high BMI levels and poor aerobic fitness. As the schools participated in the health programme on voluntary basis and at a financial cost to themselves, the positive effects of participation found can only be stated to be valid among students from committed schools.  相似文献   

Effect of positioning on the accuracy of decision making of association football top-class referees and assistant referees during competitive matches   总被引：1，自引：1，他引：0  

J Mallo  PG Frutos  D Juárez  E Navarro 《Journal of sports sciences》2012,30(13):1437-1445

Abstract The aim of this study was to examine the effect of positioning on the correctness of decision making of top-class referees and assistant referees during international games. Match analyses were carried out during the Fédération Internationale de Football Association (FIFA) Confederations Cup 2009 and 380 foul play incidents and 165 offside situations were examined. The error percentage for the referees when indicating the incidents averaged 14%. The lowest error percentage occurred in the central area of the field, where the collaboration of the assistant referee is limited, and was achieved when indicating the incidents from a distance of 11-15?m, whereas this percentage peaked (23%) in the last 15-min match period. The error rate for the assistant referees was 13%. Distance of the assistant referee to the offside line did not have an impact on the quality of the offside decision. The risk of making incorrect decisions was reduced when the assistant referees viewed the offside situations from an angle between 46 and 60°. Incorrect offside decisions occurred twice as often in the second as in the first half of the games. Perceptual-cognitive training sessions specific to the requirements of the game should be implemented in the weekly schedule of football officials to reduce the overall error rate.  相似文献   

Self-control of task difficulty during training enhances motor learning of a complex coincidence-anticipation task     

Andrieux M  Danna J  Thon B 《Research quarterly for exercise and sport》2012,83(1):27-35

The aim of the present work was to analyze the influence of self-controlled task difficulty on motor learning. Participants had to intercept three targets falling at different velocities by displacing a stylus above a digitizer Task difficulty corresponded to racquet width. Half the participants (self-control condition) could choose the racquet width at the beginning of each trial. Each was paired with a participant from the yoked group. The self-control condition resulted in better performances and accuracy during immediate and delayed retention tests. These results confirm the advantage of a self-control condition on motor learning. They are discussed with reference to the challenge point hypothesis (Guadagnoli & Lee, 2004).  相似文献   

The interaction of functional and dysfunctional emotions during balance beam performance     

Cottyn J  De Clercq D  Crombez G  Lenoir M 《Research quarterly for exercise and sport》2012,83(2):300-307

The interaction between functional and dysfunctional emotions, as one of the major tenets of the individual zones of optimal functioning (IZOF) model (Hanin, 2000), was studied in a sport specific setting. Fourteen female gymnasts performed three attempts of a compulsory balance beam routine at three different heights. Heart rate and self-report of functional and dysfunctional emotions were measured during each routine. These data revealed the effectiveness of inducting emotions by manipulating height. Also, performance decreased on the most challenging condition, (i.e., the first attempt on the highest height). Moderated hierarchical regression analysis revealed a significant interaction between functional and dysfunctional emotions only when the dysfunctional emotion level was low.  相似文献   

PAT RILEY 传奇永铸     

马克·斯特因  以色列·古铁雷斯  凯文·阿诺维茨  亨利·阿伯特  J.A.阿丹德  布莱恩·温德霍斯特 《当代体育》2012,(26):42-45

帕特·莱利常为NBA的老球迷津津乐道的莫过于,他既有执教"SHOW TIME"的湖人队在八十年代夺取四次总冠军时英俊潇洒的一面,也有带领肮脏粗野的尼克斯队在九十年代打出铁血篮球的强硬狡猾的另一面。迄今为止,过去十七个赛季在迈阿密的工作是莱利的职业生涯中做过最长的。在这期间,他做过两次主教练,一次总经理,推倒重建热火一次又一次。从2008年至今,作为主席莱利最得意的杰作莫过于组建成现在这支三巨头带领的迈阿密热火,这支球队已经连续两个赛季打入总决赛了。上次热火问鼎总冠军还是六年前,莱利执教的以韦德和奥尼尔为核心的球队。我们的六位作家就他们各自的角度来描绘帕特·莱利,而主题只有一个:传奇永驻。  相似文献   

长期体育锻炼对中青年女性骨质状况及身体成分影响     

郑盼盼  刘海平 《精武》2012,(14):14-15

目的：本研究通过对比研究长期参加体育锻炼与久坐中青年士性的身体成分和量质状况,探究体育锻炼对于改善中青年女性身体成分和量质状况的作用。方法：本研究将34名受试者分为两组,一组为体育锻炼组（exercise group,EG,17人）,另一组为久坐组（sedentary group ,5G,17人）。分别测试两组受试者身体成分和骨密度指标。结果：EG教师体内水分含量、肌肉含量、蚕白质、无机盐、体脂肪、体脂百分比和骨密度指标明卫好高于SG（P〈0．05,P〈0．01）。两组教师身体质量参文和腰臀比无显著差别（P〉0．05）。结论：EG的身体成分和骨密度指标明量好于SG,提示中青年女性可通过规律性的运动,来最防肥胖、骨质疏松等疾病,从而达到改善体质水平。  相似文献   

Calling controversy: assessing synthetic biology's conflict potential     

Torgersen H  Hampel J 《Public understanding of science (Bristol, England)》2012,21(2):134-148

Will synthetic biology elicit controversies similar to those of genetically modified crops before? Maybe, but where exactly are the analogies, and how can we gain substantial insights rather than mere guesses? We argue that as well as the intrinsic properties of the technologies at stake, the context of their implementation is decisive. To assess mechanisms of past and potential controversies, an investigative tool is presented. The Gate Resonance model, derived from older models of societal conflict, allows the identification of key elements of conflict generating processes. In monitoring the developing debate on synthetic biology using this model, analogies to the case of genetically modified crops appear less convincing. So far, there are only few indications that a controversy is imminent.  相似文献