共查询到20条相似文献，搜索用时 31 毫秒
1.
Tetsuo Shimizu M. Tsuchida K. Kawai K. Takahashi K. Arakawa M. Satoh 《Sports Engineering》2009,12(1):21-30
The B-matrix method, which systematically analyses the dynamic response of non-symmetric rigid bodies, such as golf putters, is described. The three-dimensional translational and rotational accelerations of the putter face are represented by linear equations of input forces and moments represented in matrix form. The elements of the 6 × 6 B-matrix physically represent the acceleration intensity factors. This method is applied to the analysis of the putter face control mechanism. The input forces and moments are obtained by the inverse dynamics method, whilst special attention is paid to the putter face rotation, i.e. the angular acceleration around the axis of the shaft, $ \dot{w}_{ox} . $ The contribution of input forces and moments on $ \dot{w}_{ox} $ is discussed quantitatively. The results demonstrate that $ \dot{w}_{ox} $ is present even if the input force and moment are applied perpendicularly to the shaft. A cancelling mechanism to correct this motion is discussed based on the B-matrix method. 相似文献
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Michael J. Mazzoleni Claudio L. Battaglini Kerry J. Martin Erin M. Coffman Jordan A. Ekaidat William A. Wood Brian P. Mann 《Sports Engineering》2018,21(1):31-41
This study examines the viability of utilizing a dynamical system model and heuristic parameter estimation algorithm to make predictions for maximum heart rate (\(\mathrm {HR_{max}}\)) and maximal oxygen uptake (\(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\)) using data collected from a submaximal testing protocol. \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) is widely considered to be the best single measurement of overall fitness in humans. When a \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) assessment is not available, \(\mathrm {HR_{max}}\) is often used to prescribe exercise intensities for training and rehabilitation. In the absence of maximal cardiopulmonary exercise testing (CPET), \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) are typically estimated using traditional submaximal prediction methods with well-known limitations and inaccuracies. For this study, 12 regularly exercising healthy young adult males performed a bout of maximal CPET on a cycle ergometer to determine their true \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\). Participants also performed a submaximal bout of exercise at varied intensities. A dynamical system model and heuristic parameter estimation algorithm were applied to the submaximal data to estimate the participants’ \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\). The submaximal predictions were evaluated by computing the coefficient of determination \({R^2}\) and the standard error of the estimate (SEE) through comparisons with the true maximal values for \(\mathrm {HR_{max}}\) (\({R^2 = 0.96}\), SEE = 2.4 bpm) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) (\({R^2 = 0.93}\), SEE = 2.1 mL kg\(^{-1}\) min\(^{-1}\)). The results from this study suggest that a dynamical system model and heuristic parameter estimation algorithm can provide accurate predictions for \(\mathrm {HR_{max}}\) and \(\dot{\mathrm {V}}{\mathrm {O_{2max}}}\) using data collected from a submaximal testing protocol. 相似文献
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Laurent Bosquet Antoine Duchene Paul Raoul Delhors Gregory Dupont Helen Carter 《Journal of sports sciences》2013,31(6):663-670
Abstract The aim of this study was to compare maximal accumulated oxygen deficit (hereafter O2 deficit) estimated from the methods of Whipp et al. (1986), Medbo et al. (1988), and Hill et al. (1998) to determine whether they agree sufficiently to be used interchangeably. Nineteen moderately to highly trained endurance runners first performed an incremental test to exhaustion for the determination of maximal oxygen uptake ([Vdot]O2max) and peak treadmill speed, followed by six randomly ordered constant-speed tests at 95, 100, 105, 110, 110, and 120% of peak treadmill speed. All tests were separated by at least 72 h and were performed within 4 weeks. The method of Whipp produced an O2 deficit estimate that was lower than that derived from the method of Hill or Medbo (bias ± 95% limits of agreement: ?29.6 ± 36.6 and ?26.1 ± 32.8 ml · kg?1, respectively; P < 0.001). The O2 deficit did not differ between the methods of Hill and Medbo (bias ± 95% limits of agreement: 3.5 ± 41.6 ml · kg?1; n.s.). However, poor correlations (0.21 < r < 0.33; n.s.) together with wide limits of agreement between O2 deficit estimates (70 – 80% of the mean response) clearly question using these methods interchangeably. 相似文献
6.
Abstract This study documents the effect of players' dismissals on team performance in professional soccer. Our aim was to determine whether the punishment meted out for unacceptable player behaviour results in reduced team performance. The official web site of the German Soccer Association was used for coding data from games played in the first Bundesliga between the 1963 – 64 and 2003 – 04 (n = 41) seasons. A sample of 743 games where at least one red card was issued was used to test hypotheses derived from crisis theory (Bar-Eli & Tenenbaum, 1989a). Players' dismissals weaken a sanctioned team in terms of the goals and final score following the punishment. The chances of a sanctioned team scoring or winning were substantially reduced following the sanction. Most cards were issued in the later stages of matches. The statistics pertaining to outcome results as a function of game standing, game location, and time phases – all strongly support the view that teams can be considered conceptually similar to individuals regarding the link between stress and performance. To further develop the concept of team and individual psychological performance crisis in competition, it is recommended that reversal theory (Apter, 1982) and self-monitoring and distraction theories (Baumeister, 1984) be included in the design of future investigations pertaining to choking under pressure. 相似文献
7.
Dionne Matthew 《Journal of sports sciences》2013,31(8):813-821
Abstract The aim of this study was to examine the physiological demands and movement patterns of female basketball players after changes in the rules of the game. Nine varsity players were studied during nine official games. Each game was videotaped to identify the frequencies of the main movements performed, heart rate was recorded continuously, and blood samples were collected to determine blood lactate concentration when the competition rules allowed. The main results showed that the players performed on average 652 ± 128 movements per game, which corresponded to a change in activity every 2.82 s. Mean heart rate was 165 ± 9 beats · min?1 (89.1% of maximum heart rate) for total time and 170 ± 8 beats · min?1 (92.5% of maximum) for live time. Mean blood lactate concentration was 5.2 ± 2.7 mmol · l?1 (55.9% of maximum blood lactate concentration). In addition, heart rates were significantly higher in the first half than the second half of games. These results indicate: (1) a greater physiological load compared with previous studies on female players tested before the rules modification (Beam & Merrill, 1994; McArdle et al., 1971) and (2) lower movement frequencies compared with male players competing under modern rules (Ben Abdelkrim et al., 2007). These observations must be taken into account by coaches and conditioning specialists working with female players. 相似文献
8.
Abstract We analyse the evolution of the slope (critical speed) and the y-intercept (anaerobic distance capacity) of the linear distance–time relationship over a century of Olympic running performances. The distance–time relationship of each Olympic Games (1920–2004) was plotted using the performances in the 800-, 1500- and 5000-m track events. Values for critical speed and anaerobic distance capacity were determined by linear modelling. Mean performances for the 800, 1500 and 5000 m were 104.9 ± 1.5 s (1.4%), 217.2 ± 2.8 s (1.3%) and 808.9 ± 18.4 s (2.3%), respectively. Critical speed improved during the first three-quarters of the twentieth century to reach a plateau in 1984. This is in accordance with the literature (Peronnet & Thibault, 1989) and suggests that “human aerobic endurance” has improved within the century (+13.4%) and tends to stabilize. Anaerobic distance capacity was highly variable over the century (coefficient of variation = 9.4%) and did not show a linear improvement over the years as has previously been suggested (Peronnet & Thibault, 1989). This could be due to an artefact in the application of the two-parameter model to only three Olympic performances. A limitation to the use of this linear mathematical model to fit physiological data may have been demonstrated. 相似文献
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T. T. Toering M. T. Elferink-Gemser G. Jordet C. Visscher 《Journal of sports sciences》2013,31(14):1509-1517
Abstract In learning and development, self-regulation can be described as the extent to which individuals are metacognitively, motivationally, and behaviourally proactive participants in their learning process (Zimmerman, 1989, 2006). We examined the relationship between self-regulation and performance level in elite (n = 159) and non-elite (n = 285) youth soccer players aged 11–17 years (mean 14.5 years, s = 1.4). The players completed a questionnaire that assessed planning, self-monitoring, evaluation, reflection, effort, and self-efficacy. A logistic regression analysis was performed (controlling for age) to determine which self-regulatory aspects were associated with players' performance level (elite vs. non-elite). High scores on reflection and effort were associated with a higher level of performance. Findings suggest that elite players may be more aware of their strong and weak points as well as better able to translate this awareness into action. In addition, elite players appear to be more willing to invest effort into practice and competition. It is suggested that these better developed self-regulatory skills may translate into a more effective learning environment and ultimately result in an increased capacity for performance in elite players relative to their non-elite peers. 相似文献
10.
Süleyman M. Yildiz 《Journal of sports sciences》2013,31(14):1493-1502
Abstract Numerous variables influence burnout, one of which is leader–member exchange. The present study was conducted to determine whether leader–member exchange quality affects burnout in professional footballers. The study used the Leader-Member Exchange-7 scale developed by Scandura and Graen (1984) to measure leader (coach)–member (player) exchange and Pines's (2005) abbreviated version of the burnout scale developed by Pines and Aronson (1988) to measure burnout. The data were obtained from the professional players (N = 107) of six football clubs in the Turkish Secondary Football League in western Turkey. The results demonstrated that quality of leader–member exchange significantly and inversely influenced burnout of professional footballers. The study also evaluated quality of leader–member exchange in terms of three strengths of relationship (low, fair, and high) between the coach and players. Contrary to expectations, the results revealed significant differences in burnout when comparing low versus fair quality and low versus high quality, while no significant difference in burnout was observed between fair and high quality. 相似文献
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Abstract The aims of this study were twofold: (a) to determine if dispositional achievement goal orientation profiles that are reported in the literature would be observed in a sample of youth athletes, and (b) to examine potential achievement goal orientation profile differences on perceptions of the motivational climate, perceptions of peer relationships, and motivation-related responses. Male soccer players (n = 223) aged 9–12 years (mean = 10.9, s = 0.6) completed a multi-section questionnaire containing assessments of dispositional goal (task, ego) orientations, the perceived task- and ego-involving features of the motivational climate, perceived peer acceptance and friendship quality (positive friendship quality, conflict), perceived ability, soccer enjoyment, and satisfaction with one's performance and the team. Four profiles were observed that closely matched those observed by Hodge and Petlichkoff (2000), though in the present study a lower proportion of participants exhibited achievement goal profiles consisting of relatively high ego orientation. Achievement goal profile differences were found for all variables except positive friendship quality, with a general trend for those reporting relatively lower task goal orientation to exhibit less adaptive responses. Overall, the findings support achievement goal frameworks (e.g. Nicholls, 1989) and suggest that further examination of dispositional achievement goals may afford a deeper understanding of social relationships and motivational processes in youth sport. 相似文献
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Ian C. Kenny Eric S. Wallace Steve R. Otto 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):322-332
The aim of this study was to determine how shaft length affects golf driving performance. A range of drivers with lengths between 1.168 m and 1.270 m, representing lengths close to the 1.219 m limit imposed by R&;A Rules Limited (2008), were assembled and evaluated. Clubhead and ball launch conditions and drive distance and accuracy were determined for seven category 1 golfers (handicaps 0.21 ± 2.41) who performed shots on a purpose-built practice hole. As shaft length increased from 1.168 m to 1.270 m, initial ball velocity increased (+1.8 m/s, P < 0.01). Ball carry (+4.3 m, P = 0.152) also increased, although not significantly so. Furthermore, as shaft length increased, for all club comparisons there was no decrease in accuracy. Ball launch conditions of spin components and launch angle remained unaffected by shaft length. Launch angle increased (0.8°, F = 1.074, P = 0.362) as driver shaft length increased. Our results show that clubhead and ball velocity together with ball carry tended to increase with no loss of accuracy. 相似文献
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Krista Munroe-Chandler Craig Hall Graham Fishburne 《Journal of sports sciences》2013,31(14):1539-1546
Abstract Confidence has been one of the most consistent factors in distinguishing the successful from the unsuccessful athletes (Gould, Weiss, & Weinberg, 1981) and Bandura (1997) proposed that imagery is one way to enhance confidence. Therefore, the purpose of the present study was to examine the relationship between imagery use and confidence in soccer (football) players. The participants included 122 male and female soccer athletes ages 11–14 years participating in both house/recreation (n = 72) and travel/competitive (n = 50) levels. Athletes completed three questionnaires; one measuring the frequency of imagery use, one assessing generalised self-confidence, and one assessing self-efficacy in soccer. A series of regression analyses found that Motivational General-Mastery (MG-M) imagery was a signifant predictor of self-confidence and self-efficacy in both recreational and competitive youth soccer players. More specifically, MG-M imagery accounted for between 40 and 57% of the variance for both self-confidence and self-efficacy with two other functions (MG-A and MS) contributing marginally in the self-confidence regression for recreational athletes. These findings suggest that if a youth athlete, regardless of competitive level, wants to increase his/her self-confidence or self-efficacy through the use of imagery, the MG-M function should be emphasised. 相似文献
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Abstract Swain (1997) employed the mathematical model of Di Prampero et al. (1979) to predict that, for cycling time-trials, the optimal pacing strategy is to vary power in parallel with the changes experienced in gradient and wind speed. We used a more up-to-date mathematical model with validated coefficients (Martin et al., 1998) to quantify the time savings that would result from such optimization of pacing strategy. A hypothetical cyclist (mass = 70 kg) and bicycle (mass = 10 kg) were studied under varying hypothetical wind velocities (?10 to 10 m · s?1), gradients (?10 to 10%), and pacing strategies. Mean rider power outputs of 164, 289, and 394 W were chosen to mirror baseline performances studied previously. The three race scenarios were: (i) a 10-km time-trial with alternating 1-km sections of 10% and ?10% gradient; (ii) a 40-km time-trial with alternating 5-km sections of 4.4 and ?4.4 m · s?1 wind (Swain, 1997); and (iii) the 40-km time-trial delimited by Jeukendrup and Martin (2001). Varying a mean power of 289 W by ± 10% during Swain's (1997) hilly and windy courses resulted in time savings of 126 and 51 s, respectively. Time savings for most race scenarios were greater than those suggested by Swain (1997). For a mean power of 289 W over the “standard” 40-km time-trial, a time saving of 26 s was observed with a power variability of 10%. The largest time savings were found for the hypothetical riders with the lowest mean power output who could vary power to the greatest extent. Our findings confirm that time savings are possible in cycling time-trials if the rider varies power in parallel with hill gradient and wind direction. With a more recent mathematical model, we found slightly greater time savings than those reported by Swain (1997). These time savings compared favourably with the predicted benefits of interventions such as altitude training or ingestion of carbohydrate-electrolyte drinks. Nevertheless, the extent to which such power output variations can be tolerated by a cyclist during a time-trial is still unclear. 相似文献
15.
Adam R. Nicholls Remco Polman Andrew R. Levy Jamie Taylor Stephen Cobley 《Journal of sports sciences》2013,31(13):1521-1530
Abstract The aim of this study was to examine stressors, coping, and coping effectiveness as a function of gender, type of sport, and skill. The sample consisted of 749 undergraduate athletes (455 males, 294 females) aged 18 – 38 years (mean = 19.8 years). Skill was classified as international/national, county, university, and club standard. Participants completed a stressor and coping concept map (Novak & Gowin, 1984). The results revealed gender, type of sport, and skill differences in relation to stressor frequencies, coping strategy deployment, and coping effectiveness. In contrast to previous research, females used a variety of problem-focused (e.g. planning, communication, technique-orientated coping) strategies more frequently than males. Team sport athletes reported a variety of sport-specific stressors relating to the demands of playing in a team environment. The group of national/international athletes reported using more planning, blocking, and visualization, and also reported that their coping was more effective than that of less-skilled athletes. 相似文献
16.
Shinichi Demura Shunsuke Yamaji Takayuki Murooka Masuo Nakai 《Journal of sports sciences》2013,31(8):881-889
Abstract We previously proposed two predictive equations of visceral fat area applicable in a field setting (Demura & Sato, 2007a, 2007b). One uses the fat mass of the trunk measured by bioelectrical impedance as the main predictor (equation 1) and the other uses internal fat mass estimated from several anthropometric variables (equation 2). In this study, we examined the inter- and intra-individual accuracy of estimated values using these equations after 8 weeks of exercise training. Participants were 42 Japanese adults aged 42.7 ± 10.3 years (22 males, 20 females). Visceral fat area, body composition, and blood biochemistry were measured at baseline and after 8 weeks. There were no significant differences in reference visceral fat area measured by computed tomography and visceral fat area predicted by the equations either at baseline or after 8 weeks, and the values were highly consistent (equation 1: baseline R 2 = 0.829, after R 2 = 0.860; equation 2: baseline R 2 = 0.832; after R 2 = 0.850). No significant relationship was observed between the reference and change in visceral fat area for equation 1 (males: r = 0.272, P > 0.05; females: r = 0.428, P > 0.05), but there was a significant relationship for females with equation 2 (males: r = 0.279, P > 0.05; females: r = 0.474, P <0.05). Our findings indicate that these equations have high inter-individual consistency but low intra-individual consistency with the reference and are of limited use for the longitudinal evaluation of visceral fat area. 相似文献
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Abstract Coping strategies are important for performance in sport and individual differences may contribute to the coping strategies adopted by athletes. In this study, we explored the main and interactive effects of the big five personality dimensions on sport-related coping and compared personality profiles of discrete groups of athletes. Altogether, 253 athletes (mean age 21.1 years, s = 3.7) completed the NEO-FFI (Costa & McCrae, 1992), and the Coping Function Questionnaire for Sport (Kowalski & Crocker, 2001). Results showed that extraverted athletes, who were also emotionally stable and open to new experiences (a three-way interaction effect), reported a greater use of problem-focused coping strategies. Conscientious athletes (main effect), and athletes displaying high levels of extraversion, openness, and agreeableness (a three-way interaction effect), reported a greater use of emotion-focused coping strategies, and athletes with low levels of openness, or high levels of neuroticism (main effects), reported a greater use of avoidance coping strategies. Different personality characteristics were observed between higher-level and lower-level athletes, between men and women athletes, and between individual and team sport athletes. These findings suggest that the five-factor model of personality can help distinguish various levels of athletic involvement and can help identify the coping strategies athletes are likely to adopt during participation. 相似文献
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Gökçe Erturan İlker Yunus Arslan Gıyasettin Demirhan 《Measurement in physical education and exercise science》2013,17(4):301-313
The Trichotomous Achievement Goal Scale was developed by Agbuga and Xiang (2008) by including selected items from the scales of Duda and Nicholls (1992), Elliot (1999), and Elliot and Church (1997) and adapting them into Turkish. The scale consists of 18 items, and students rated each item on a 7-point Likert scale. To ascertain the validity and reliability of the Trichotomous Achievement Goal Scale, it was administered to 845 female and 861 male Turkish high school students attending three public schools in the 2008–2009 spring semester. Exploratory and confirmatory factor analyses were conducted, and Cronbach's alpha and Fornell and Larcker's (1981) criteria were tested on the items that measured the students' achievements, screening for the three distinct types of achievement goals proposed by the trichotomous framework. Based on the results of the study, the 16-item Trichotomous Achievement Goal Scale can be claimed as a valid a reliable scale. 相似文献
19.
Abstract Oudejans, Bakker, and Beek (2007) recognize several relevant aspects of offside judgements in association football in the paper by Helsen, Gilis, and Weston (2006). We agree that the existing knowledge base on offside assessment needs to be expanded for two reasons. First, from a theoretical point of view it is important to examine how assistant referees can learn to deal with the limitations of the human visual information processing system. Second, from a practical point of view it is relevant to understand better refereeing performances and to identify potential explanations for incorrect offside decisions that could impact on the final outcome of the game. Oudejans et al. (2007) believe we both misinterpreted the optical error hypothesis and that our data set was unsuited to test it. Below, we react to these comments. 相似文献
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《International review of sport and exercise psychology》2013,6(1):45-57
The area of competitive anxiety continues to be extensively researched with considerable attention focused on the notion of ‘direction’. The purpose of this review is to demonstrate how the study of direction has advanced our understanding of the competitive anxiety response through providing an overview of the existing research, and emphasizing why sport psychologists investigated the underlying mechanisms of performers’ facilitative interpretations of anxiety symptoms. Finally, we discuss how direction has been integrated into Lazarus (1990, 1991a); Lazarus & Folkman, 1984) transactional perspective of stress, and how this may be used to inform future research into the broader area of competition stress. 相似文献