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41.
Relationship between world-ranking and Olympic performance of swimmers   总被引:1,自引:0,他引:1  
Coaches believe world-ranking lists are a reliable tool for predicting international swimming performance. To examine the relationship between world-ranking and Olympic performance, we modelled world-ranking time and best time from the 2000 Olympic Games for 407 top-50 world-ranked swimmers. Analysis of log-transformed times yielded within-athlete and between-athlete coefficients of variation (CV) and percent changes in performance from world-rankings to Olympics. Variations and performance progressions were compared across sex, stroke, distance, nation and medal status. The within-athlete coefficient of variation of performance for all swimmers was 0.8% (95% confidence limits: 0.7 to 0.9%). Females were slightly less consistent, although not substantially different to males (ratio of female/male within-athlete CV: 1.1; 95% confidence limits: 1.0 to 1.2) and had a wider range of talent (ratio of female/male between-athlete CV: 1.2; 95% confidence limits: 1.1 to 1.4). Swimmers from Australia (AUS) were more consistent than those from the United States (USA) and other nations (OTHER) (ratio of within-athlete CV, USA/AUS: 1.5; 95% confidence limits: 1.0 to 2.2; OTHER/ AUS: 1.6; 95% confidence limits: 1.2 to 2.1). Most Olympic medallists (87%) had a top-10 world-ranking. Overall performance time at the Olympics was slower than world-ranking time by 0.3% (95% confidence limits: 0.2 to 0.4%), medallists improved by 0.6% (95% confidence limits: 0.4 to 0.9%) and non-medallists swam 0.6% slower (95% confidence limits: 0.5 to 0.7%). We conclude that a top-10 ranked swimmer who can improve performance time by 0.6%, equivalent to 0.13 s in the men's 50-m freestyle, will substantially increase their chance of an Olympic medal (the difference between first and fourth place).  相似文献   
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Abstract

In this study, we wished to investigate the factors that determine the direction of the spin axis of a pitched baseball. Nineteen male baseball pitchers were recruited to pitch fastballs. The pitching motion was recorded with a three-dimensional motion analysis system (1000 Hz), and the orientations of the hand segment in a global coordinate system were calculated using Euler rotation angles. Reflective markers were attached to the ball, and the direction of the spin axis was calculated on the basis of their positional changes. The spin axis directions were significantly correlated with the orientations of the hand just before ball release. The ball is released from the fingertip and rotates on a plane that is formed by the palm and fingers; the spin axis of the ball is parallel to this plane. The lift force of the pitched baseball is largest when the angular and translational velocity vectors are mutually perpendicular. Furthermore, to increase the lift forces for the fastballs, the palm must face home plate.  相似文献   
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Abstract

The purpose of this study was to compare moment-to-moment appraisals and coping strategies of 4 non-elite and 2 elite male trap shooters during competitions and in particular during periods of competition perceived as critical to performance. Appraisals and coping patterns of trap shooters were captured via verbal reports of thinking provided between sets of shots during major competitions. Verbal reports were coded according to an appraisal and coping typology. Coded data as well as shooting performance data were subjected to a sequential analysis of probabilities of pairs of events. Fewer reports of negative appraisals (NEGAs) and more frequent reports of problem-focused coping (PFC) were observed among both elite athletes compared to non-elite athletes. After making a NEGA, non-elite shooters often progressed to the next target without attempting to cope, whereas elite shooters used both PFC and emotion-focused coping (EFC) before proceeding to the next target. After missing a target, the non-elite athletes used more EFC than expected. These results indicate that elite athletes are more likely to cope with NEGAs than non-elite athletes using a wider variety of coping strategies. Athletes might benefit from increased awareness of the potentially detrimental impact of NEGAs on performance and by integrating coping strategies within preparatory routines.  相似文献   
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Abstract

The purpose of this study was to observe the effects of a progressive aerobic training program on hemoglobin concentration (Hb), hematocrit (Hct), red blood cell (RBC) count, mean RBC size (MCV), and mean corpuscular hemoglobin (MCH) of college women (N = 19). Training consisted of jogging (3 × week) one mile per session (Week 1) with a progressive increase in duration to five miles per session (Week 9). Training intensity elicited heart rates between 165–185 beats per minute. Blood samples were taken before training and after approximately two, five, seven, and nine weeks. Maximal oxygen uptake (ml/kg · min?1) increased significantly during training from 41.2 ± 0.7 ( ± SE) to 44.7 ± 0.7. Initial values of Hb, Hct, RBC count, MCV, and MCH were 14.7 ± 0.13 g/dl, 40.4 ± 0.46%, 4.5 ± 0.5 × 106/mm3, 89.0 ± 1.1/μ3, and 32.4 ± 0.4 μμg respectively. Orthogonal polynominal regression indicated significant decreasing quadratic trends for Hb, Hct, and RBC count, a significant cubic trend for MCV, and no change in MCH during training. Despite the initial trends, values that changed did return to near pretraining levels by the end of the nine-week program. Values for all blood parameters remained within normal ranges throughout the study. These data suggest that although aerobic training of increasing intensity in young women may be accompanied initially by decreases in Hb, Hct, and RBC count and an increase in MCV, these changes are only transitory. If such changes result from RBC destruction rather than hemodilution, the return to hematopoietic balance could impose a draw on body iron stores.  相似文献   
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