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161.
A growing body of literature is devoted to testing the reality of the “long-tail” phenomenon. This literature is mostly, if not exclusively, focused on the impact of Internet on the distribution of sales by product. However, the long tail also raises the issue of a possible change in the usual market structure of cultural industries: an oligopoly with a competitive fringe. To our knowledge, no paper addresses the following question: If the long-tail effect does exist, is it of more benefit to small or dominant publishers? The aim of this paper was to address this issue in the context of the French publishing industry. Our main findings are as follows: (1) the market concentration of the French book industry is lower online than offline and (2) the difference in concentration between the two channels of distribution tended to widen over the period 2004–2010. Strategies adopted by leading publishers on the Web do not allow them to maintain the market share obtained with bricks-and-mortar retailers. Furthermore, we show that the market share lost by dominant firms is captured by small publishers online and by medium-sized publishers in conventional stores.  相似文献   
162.
The prevalence of ischaemia-related symptoms is remarkably high among elite indoor volleyball players. Since the exposure to sport-specific demands may be higher in beach volleyball compared to indoor volleyball, the aim of this study was to assess the prevalence of ischaemia-related symptoms and associated risk factors among world-class beach volleyball players. Therefore, a questionnaire survey was performed among beach volleyball players active during the 2013 Grand Slam Beach Volleyball in the Netherlands. In total, 60 of the 128 beach volleyball players (47%) participated: 26 males and 34 females from 17 countries. The self-reported prevalence of cold or blue or pale digits in the dominant hand during or immediately after practice or competition was 38% (n = 23). Two risk factors were independently associated with symptoms of blue or pale digits: more than 14 years playing volleyball (odds ratio (OR) 4.42, 90% confidence interval (90% CI) 1.30–15.07) and sex (female) (OR 4.62, 90% CI 1.15–18.57). In conclusion, the prevalence of symptoms associated with digital ischaemia is high among international world-class beach volleyball players. Female sex and the length of the volleyball career were independently associated with an increased risk of ischaemia-related symptoms. The high prevalence of these seemingly innocuous symptoms and possible associated risk factors warrant regular monitoring since early detection can potentially prevent thromboembolic complications and irreversible tissue damage.  相似文献   
163.
Research examining our ability to avoid obstacles in our path has stressed the importance of visual input. The aim of this study was to determine if athletes playing varsity-level field sports, who rely on visual input to guide motor behaviour, are more able to guide their foot over obstacles compared to recreational individuals. While wearing kinematic markers, eight varsity athletes and eight age-matched controls (aged 18–25) walked along a walkway and stepped over stationary obstacles (180° motion arc). Visual input was manipulated using PLATO visual goggles three or two steps pre-obstacle crossing and compared to trials where vision was given throughout. A main effect between groups for peak trail toe elevation was shown with greater values generated by the controls for all crossing conditions during full vision trials only. This may be interpreted as athletes not perceiving this obstacle as an increased threat to their postural stability. Collectively, findings suggest the athletic group is able to transfer their abilities to non-specific conditions during full vision trials; however, varsity-level athletes were equally reliant on visual cues for these visually guided stepping tasks as their performance was similar to the controls when vision is removed.  相似文献   
164.
ABSTRACT

The objective of this study was to create a valid, self-reported, game-specific soccer competence scale. A structural model of perceived competence, performance measures and motivation was tested as the basis for the scale. A total of 1321 soccer players (261 females, 1060 males) ranging from 12 to 15 years (13.4 ± 1.0 years) participated in the study. They completed the Perceived Game-Specific Soccer Competence Scale (PGSSCS), self-assessments of tactical skills and motivation, as well as technical and speed and agility tests. Results of factor analyses, tests of internal consistency and correlations between PGSSCS subscales, performance measures and motivation supported the reliability and validity of the PGSSCS. The scale can be considered a suitable instrument to assess perceived game-specific competence among young soccer players.  相似文献   
165.
Given that physical activity (PA) tends to decrease with age during adolescence, addressing factors that affect change is important. This study examined the similarity and interdependence of PA as influenced by psychosocial factors among adolescent best friend dyads. A total of 660 adolescents, representing 330 best friend dyads, completed questionnaires with regard to PA, sitting time, perceived exercise benefits and barriers, physical self-perception and social support for PA. Dyads were also identified as reciprocal and non-reciprocal best friends; reciprocal means that both considered each other best friends and non-reciprocal were those in which only one considered the other a best friend. Data were analysed using a hierarchical linear model framework. Results indicated significant similarities between reciprocal best friend dyads for PA and sitting time, and for sitting time in non-reciprocal best friends (P values <.01). Psychosocial variables were associated with PA in reciprocal best friend dyads and with sitting time in reciprocal and non-reciprocal best friend dyads. Best friend gender, regular sports practice of the person, perceived exercise barriers of the best friend and best friend social support were the best predictors for PA.  相似文献   
166.
ABSTRACT

The objective of this 1-year, longitudinal study was to examine the development of perceived competence, tactical skills, motivation, technical skills, and speed and agility characteristics of young Finnish soccer players. We also examined associations between latent growth models of perceived competence and other recorded variables. Participants were 288 competitive male soccer players ranging from 12 to 14 years (12.7 ± 0.6) from 16 soccer clubs. Players completed the self-assessments of perceived competence, tactical skills, and motivation, and participated in technical, and speed and agility tests. Results of this study showed that players’ levels of perceived competence, tactical skills, motivation, technical skills, and speed and agility characteristics remained relatively high and stable across the period of 1 year. Positive relationships were found between these levels and changes in perceived competence and motivation, and levels of perceived competence and speed and agility characteristics. Together these results illustrate the multi-dimensional nature of talent development processes in soccer. Moreover, it seems crucial in coaching to support the development of perceived competence and motivation in young soccer players and that it might be even more important in later maturing players.  相似文献   
167.
In sports, fast and accurate execution of movements is required. It has been shown that implicitly learned movements might be less vulnerable than explicitly learned movements to stressful and fast changing circumstances that exist at the elite sports level. The present study provides insight in explicit and implicit motor learning in youth soccer players with different expertise levels. Twenty-seven youth elite soccer players and 25 non-elite soccer players (aged 10–12) performed a serial reaction time task (SRTT). In the SRTT, one of the sequences must be learned explicitly, the other was implicitly learned. No main effect of group was found for implicit and explicit learning on mean reaction time (MRT) and accuracy. However, for MRT, an interaction was found between learning condition, learning phase and group. Analyses showed no group effects for the explicit learning condition, but youth elite soccer players showed better learning in the implicit learning condition. In particular, during implicit motor learning youth elite soccer showed faster MRTs in the early learning phase and earlier reached asymptote performance in terms of MRT. Present findings may be important for sports because children with superior implicit learning abilities in early learning phases may be able to learn more (durable) motor skills in a shorter time period as compared to other children.  相似文献   
168.
The aim of this study was to investigate how the type of contact influences physiological, perceptual and locomotive load during a simulated rugby league match. Eleven male university rugby league players performed two trials of the rugby league movement simulation protocol for interchange forwards with a traditional soft tackle bag and a weighted tackle sled to replicate contact demands. The interchange forward-specific simulation was chosen given the contact frequency is higher for this group of players compared to whole match players. Locomotive rate, sprint speed, tackle intensity, heart rate (HR) and rating of perceived exertion were analysed during the first and second bouts that replicated two ~23 min on-field passages. Countermovement jump (CMJ) was measured before and immediately after each trial. More time was spent in heart rate zone between 91 and 100% HRpeak during the first (effect size ± 90% confidence interval: 0.44 ± 0.49) and second bouts (0.44 ± 0.43), and larger (0.6 ± 0.69) decrements in CMJ performance were observed during the sled trial (5.9, = 4.9%) compared to the bag trial (2.6, = 5.4%). Changing the type of contact during the match simulation subtly altered both the internal and external loads on participants. Using a standard tackle bag results in faster sprint speed to contact, but lower overall high-intensity running. Conversely, a heavier tackle object increases the internal load and results in greater lower limb neuromuscular fatigue as reflected by the decrease in CMJ performance.  相似文献   
169.
While the career experiences and trajectories of various sports workers have received increased scholarly attention, those of professional coaches have, in comparison, received scant consideration. This paper focuses on the career experiences of Maeve (a pseudonym), a high performance coach, and the critical incidents related to the creation, development, and, ultimately, questioning of her professional identity. Data were collected through a series of narrative-biographical interviews and were subject to a process of iterative data analysis. The results indicated that her significant investment into her coaching self, combined with the vagaries and uncertain nature of work in high performance coaching, led her to experience a biographical disruption that interrupted the narrative coherence of her coaching life. The findings add further credence to recent critiques of only understanding and representing coaching careers in a linear and chronically staged fashion.  相似文献   
170.
Limited recommendations of wheelchair configurations for court sports have been identified in the published literature. To accommodate the wide range of impairments in wheelchair rugby, players are given a point score that reflects their impairment. Players have regularly been grouped as high-, mid-, or low-point players in research, with high-point players having greater levels of muscle function compared with other classifications. This research documented the wheelchair configurations of elite Australian wheelchair rugby players across classification groups. Significant differences (p < 0.05) were found for increased seat height and decreased seat depth for high-point players compared with low- and mid-point groups, respectively. Low-point players displayed reduced wheelchair mass compared with high- and mid-point players, as well as increased frame length. Camber angles showed no significant differences across the classification groups. The incorporation of anthropometric measures, such as the elbow angle at the top dead center, was also investigated. While elbow angle showed no significant differences, seat height-to-total arm length ratio was higher for high-point players. Participants also completed surveys detailing their perception of the effect of altering wheelchair configurations. It is suggested that wheelchair configurations should consider an individual’s anthropometrics, impairment, training history, and court role to promote optimal performance, with predictive modeling having the potential to reduce the associated time and cost.  相似文献   
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