Mechanical jurisprudence.—No. IX     

Peter A. Browne 《Journal of The Franklin Institute》1826,(4):228-236

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网球比赛分析的几个关键点     

王磊 《中国体育教练员》2009,17(2)

许多运动队将全程比赛分析作为教练员的指导工具,研究己方和对方运动员的类型、战术和技术特点.网球项目中,拥有个人分析师的运动员并不多见,大部分运动员和教练员使用分析设备和程序提供的客观、可靠的反馈信息,自己进行赛前及赛后分析.很多教练员采用其他教练员的有效训练模式,因为不是所有人都有时间去分析1000h的大满贯录像来找出战术差异,但可利用他人的分析结果.赛事录像记录的客观数据提供了充足的反馈信息,教练员可根据这些反馈信息调整技战术,进行针对性的训练.  相似文献   

Nutritional strategies to optimize training and racing in middle-distance athletes     

Stellingwerff T  Boit MK  Res PT;International Association of Athletics Federations 《Journal of sports sciences》2007,25(Z1):S17-S28

Middle-distance athletes implement a dynamic continuum in training volume, duration, and intensity that utilizes all energy-producing pathways and muscle fibre types. At the centre of this periodized training regimen should be a periodized nutritional approach that takes into account acute and seasonal nutritional needs induced by specific training and competition loads. The majority of a middle-distance athlete's training and racing is dependant upon carbohydrate-derived energy provision. Thus, to support this training and racing intensity, a high carbohydrate intake should be targeted. The required energy expenditure throughout each training phase varies significantly, and thus the total energy intake should also vary accordingly to better maintain an ideal body composition. Optimizing acute recovery is highly dependant upon the immediate consumption of carbohydrate to maximize glycogen resynthesis rates. To optimize longer-term recovery, protein in conjunction with carbohydrate should be consumed. Supplementation of beta-alanine or sodium bicarbonate has been shown to augment intra- and extracellular buffering capacities, which may lead to a small performance increase. Future studies should aim to alter specific exercise (resistance vs. endurance) and/or nutrition stimuli and measure downstream effects at multiple levels that include gene and molecular signalling pathways, leading to muscle protein synthesis, that result in optimized phenotypic adaptation and performance.  相似文献   

Nutrition for the sprinter     

Tipton KD  Jeukendrup AE  Hespel P;International Association of Athletics Federations 《Journal of sports sciences》2007,25(Z1):S5-15

The primary roles for nutrition in sprints are for recovery from training and competition and influencing training adaptations. Sprint success is determined largely by the power-to-mass ratio, so sprinters aim to increase muscle mass and power. However, extra mass that does not increase power may be detrimental. Energy and protein intake are important for increasing muscle mass. If energy balance is maintained, increased mass and strength are possible on a wide range of protein intakes, so energy intake is crucial. Most sprinters likely consume ample protein. The quantity of energy and protein intake necessary for optimal training adaptations depends on the individual athlete and training demands; specific recommendations for all sprinters are, at best, useless, and are potentially harmful. However, if carbohydrate and fat intake are sufficient to maintain energy levels, then increased protein intake is unlikely to be detrimental. The type and timing of protein intake and nutrients ingested concurrently must be considered when designing optimal nutritional strategies for increasing muscle mass and power. On race day, athletes should avoid foods that result in gastrointestinal discomfort, dehydration or sluggishness. Several supplements potentially influence sprint training or performance. Beta-alanine and bicarbonate may be useful as buffering agents in longer sprints. Creatine may be efficacious for increasing muscle mass and strength and perhaps increasing intensity of repeat sprint performance during training.  相似文献   

Relational efficacy beliefs in athlete dyads: an investigation using actor-partner interdependence models     

Jackson B  Beauchamp MR  Knapp P 《运动与训练心理学杂志》2007,29(2):170-189

The first purpose of this study was to examine the interrelationships among three forms of relational efficacy within performing dyads, namely, self-efficacy, other-efficacy, and relation-inferred self-efficacy. The second objective was to examine the relationships between these efficacy beliefs and athletes' perceptions of their commitment to and satisfaction with their current partnership. Participants were 120 junior tennis players (age, M = 14.30 years, SD = 1.21) performing within 60 intact pairs (i.e., doubles). Results revealed that self-efficacy and other-efficacy were predictive of athlete commitment and satisfaction, respectively. In addition, by utilizing actor-partner interdependence models, partner as well as actor effects were evident. The findings illustrate that relational efficacy beliefs may not only have implications for the individual holding such beliefs, but also for his or her relational partner. Implications for the future study of efficacy beliefs within dyadic contexts are discussed.  相似文献   

Anthropometric dimensions of male powerlifters of varying body mass   总被引：1，自引：1，他引：0  

Keogh JW  Hume PA  Pearson SN  Mellow P 《Journal of sports sciences》2007,25(12):1365-1376

In this study, we examined the anthropometric dimensions of powerlifters across various body mass (competitive bodyweight) categories. Fifty-four male Oceania competitive powerlifters (9 lightweight, 30 middleweight, and 15 heavyweight) were recruited from one international and two national powerlifting competitions held in New Zealand. Powerlifters were assessed for 37 anthropometric dimensions by ISAK (International Society for the Advancement of Kinanthropometry) level II and III accredited anthropometrists. The powerlifters were highly mesomorphic and had large girths and bony breadths, both in absolute units and when expressed as Z(p)-scores compared through the Phantom (Ross & Wilson, 1974). These anthropometric characteristics were more pronounced in heavyweights, who were significantly heavier, had greater muscle and fat mass, were more endo-mesomorphic, and had larger girths and bony breadths than the lighter lifters. Although middleweight and heavyweight lifters typically had longer segment lengths than the lightweights, all three groups had similar Zp-scores for the segment lengths, indicating similar segment length proportions. While population comparisons would be required to identify any connection between specific anthropometric dimensions that confer a competitive advantage to the expression of maximal strength, anthropometric profiling may prove useful for talent identification and for the assessment of training progression in powerlifting.  相似文献   

Biomechanics of aggressive inline skating: landing and balancing on a grind rail     

Major MJ  Beaudoin AJ  Kurath P  Hsiao-Wecksler ET 《Journal of sports sciences》2007,25(12):1411-1422

Currently, only epidemiological injury data have been reported for the new extreme sport of aggressive inline skating, or trick skating. No studies have examined the biomechanics of this sport, which involves repetitive jumping and landing from railings, ramps, and ledges, often over 1 m in height. We present results of a pilot study that examined the effect of skater experience and lower extremity biomechanics on energy absorption ability, and observed balance strategies used during two basic tricks. In these tricks, the skater jumps onto an elevated rail and maintains balance while standing in a single position (stall) or sliding along the rail (grind). Lower extremity joint kinematics, impact force characteristics, and general movement behaviours were examined during landing and balance phases. Ten male skaters performed ten stalls and ten frontside grinds on an instrumented grind rail, capable of measuring vertical force. Vertical impact force was found to decrease with increasing skater experience in stalls (r = -0.84, P = 0.002) and grinds (r = -0.84, P = 0.009). This might imply that less-experienced skaters are (subconsciously) more concerned about maintaining balance than refining technique to minimize impact force. Similar to drop landing experiments, peak impact force decreased with increasing knee flexion during stalls (r = -0.65, P = 0.04). During stalls, skaters demonstrated classic balance maintenance strategies (ankle, hip, or multi-joint) depending on trick length. During grinds, skater centre of mass never passed over the rail base of support, suggesting the use of momentum produced from obliquely approaching the rail.  相似文献   

Helsen, Gilis and Weston (2006) err in testing the optical error hypothesis     

Oudejans RR  Bakker FC  Beek PJ 《Journal of sports sciences》2007,25(9):987-990

In this commentary, we react to the recent study by Helsen, Gilis and Weston (2006) on judging offside in football. Helsen et al. claim that their data falsify the optical error hypothesis presented by Oudejans et al. (2000). However, as we will elucidate here, they misinterpret this hypothesis and present a data set that is seriously flawed, and hence not suited to test it. Therefore, their conclusions regarding the optical error hypothesis are in error.  相似文献   

Elite football on artificial turf versus natural grass: movement patterns, technical standards, and player impressions     

Andersson H  Ekblom B  Krustrup P 《Journal of sports sciences》2008,26(2):113-122

The aim of the present study was to examine the movement patterns, ball skills, and the impressions of Swedish elite football players during competitive games on artificial turf and natural grass. Time - motion analyses (36 observations) and technical analyses (16 team observations) were performed and 72 male and 21 female players completed a questionnaire. No differences were observed between artificial turf and natural grass in terms of total distance covered (mean 10.19 km, s = 0.19 vs. 10.33 km, s = 0.23), high-intensity running (1.86 km, s = 0.10 vs. 1.87 km, s = 0.14), number of sprints (21, s = 1 vs. 22, s = 2), standing tackles (10, s = 1 vs. 11, s = 1) or headers per game (8, s = 1 vs. 8, s = 1), whereas there were fewer sliding tackles (P < 0.05) on artificial turf than natural grass (2.1, s = 0.5 vs. 4.3, s = 0.6). There were more short passes (218, s = 14 vs. 167, s = 12) and midfield-to-midfield passes (148, s = 11 vs. 107, s = 8) (both P < 0.05) on artificial turf than natural grass. On a scale of 0-10, where 0 = "better than", 5 = "equal to", and 10 = "worse than", the male players reported a negative overall impression (8.3, s = 0.2), poorer ball control (7.3, s = 0.3), and greater physical effort (7.2, s = 0.2) on artificial turf than natural grass. In conclusion, the running activities and technical standard were similar during games on artificial turf and natural grass. However, fewer sliding tackles and more short passes were performed during games on artificial turf. The observed change in playing style could partly explain the male players' negative impression of artificial turf.  相似文献   

Report to the directors of the London and Birmingham Railway Company,accompanied by experiments on the transverse strength, &c. of malleable iron,with reference to its use for railway bars     

Peter Barlow 《Journal of The Franklin Institute》1835,20(2):118-127

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