Influence of a stressing constraint on stiffness and damping functions of a ski simulator's platform motion     

Deschamps T  Nourrit D  Caillou N  Delignières D 《Journal of sports sciences》2004,22(9):867-874

The aim of this study was to assess the effect of stress on a previously acquired motor coordination. Following a longitudinal learning experiment, four participants performed oscillations on a ski simulator, either in normal or stressful conditions. The results showed that the amplitude of the oscillations decreased under stress, but no significant effect was seen regarding coordination, suggesting the strong resistance to stress of overlearned behaviour. Nevertheless, for one participant, a transient regression towards a former stage of learning was observed. This result was consistent with the regression hypothesis formulated by Fuchs (1962).  相似文献   

Effects of modified-implement training on fast bowling in cricket     

Petersen CJ  Wilson BD  Hopkins WG 《Journal of sports sciences》2004,22(11-12):1035-1039

The effects of training with overweight and underweight cricket balls on fast-bowling speed and accuracy were investigated in senior club cricket bowlers randomly assigned to either a traditional (n = 9) or modified-implement training (n = 7) group. Both groups performed bowling training three times a week for 10 weeks. The traditional training group bowled only regulation cricket balls (156 g), whereas the modified-implement training group bowled a combination of overweight (161-181 g), underweight (151-131 g) and regulation cricket balls. A radar gun measured the speed of 18 consecutive deliveries for each bowler before, during and after the training period. Video recordings of the deliveries were also analysed to determine bowling accuracy in terms of first-bounce distance from the stumps. Bowling speed, which was initially 108 +/- 5 km h(-1) (mean +/- standard deviation), increased in the modified-implement training group by 4.0 km x h(-1) and in the traditional training group by 1.3 km x h(-1) (difference, 2.7 km x h(-1); 90% confidence limits, 1.2 to 4.2 km x h(-1)). For a minimum worthwhile change of 5 km x h(-1), the chances that the true effect on bowling speed was practically beneficial/trivial/harmful were 1.0/99/< 0.1%. For bowling accuracy, the chances were 1/48/51%. This modified-implement training programme is not a useful training strategy for club cricketers.  相似文献   

String vibration dampers do not reduce racket frame vibration transfer to the forearm     

Li FX  Fewtrell D  Jenkins M 《Journal of sports sciences》2004,22(11-12):1041-1052

In this study, we examined the effect of string vibration damping devices on reducing racket frame vibration transfer to the forearm. Twenty participants volunteered to hold a tennis racket stationary in a forehand and backhand stroking position while tennis balls were fired at 20 m x s(-1) towards two impact locations, the node of vibration and the dead spot. A three-way analysis of variance with repeated measures on damping condition, impact location and stroke condition was performed on the data. The resonant frequency of the hand-held racket was found to be approximately 120 Hz. No significant differences in amplitude of vibration at the resonant frequency were found for the wrist or the elbow when damped and non-damped impacts were compared. Impacts at the dead spot produced greater amplitudes of vibration (P < 0.01) but no interaction between impact location and string dampers was evident. The string dampers had no effect on the grip force used or the muscle electrical activity in the forearm after impact. In conclusion, we found that string dampers do not reduce the amount of racket frame vibration received at the forearm. We suggest that string dampers remain a popular accessory among tennis players because of their acoustic effects and psychological support rather than any mechanical advantage.  相似文献   

Relationship between world-ranking and Olympic performance of swimmers   总被引：1，自引：0，他引：1  

Trewin CB  Hopkins WG  Pyne DB 《Journal of sports sciences》2004,22(4):339-345

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   

Protein and amino acid requirements of athletes     

Millward DJ 《Journal of sports sciences》2004,22(1):143-144

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Physiological and metabolic responses of wheelchair athletes in different racing classes to prolonged exercise     

Campbell IG  Williams C  Lakomy HK 《Journal of sports sciences》2004,22(5):449-456

The aims of this study were to examine and compare selected physiological and metabolic responses of wheelchair athletes in two paraplegic racing classes [T3: n = 8 (lesion levels T1-T7; paraplegics); T4: n = 9 (lesion levels below T7; paraplegics)] to prolonged exercise. In addition, we describe the responses of three tetraplegic athletes [T2: n = 3 (lesion levels C6/C7: tetraplegics)]. Twenty athletes completed 90 min of exercise at 75% VO2peak on a motorized treadmill adapted for wheelchairs. The mean (+/- s) heart rates of the T3 and T4 racing classes were 165 +/- 2 and 172 +/- 6 beats.min-1, respectively. For the T4 racing class, heart rate gradually increased during the test (P < 0.05), whereas for the T3 racing class, heart rate reached a plateau after an initial increase. The mean heart rate of the tetraplegics was 114 +/- 3 beats.min-1. The T3 and T4 classes exhibited similar respiratory exchange ratios, plasma lactate and glucose concentrations throughout the test. For both the T3 and T4 racing class, free fatty acid, glycerol, ammonia, urea and potassium concentrations had increased from resting values by the end of the test (P < 0.05). In conclusion, the results of this study suggest that endurance-trained wheelchair athletes are able to maintain velocities equivalent to the same relative exercise intensity (75% VO2peak) for prolonged periods irrespective of lesion level.  相似文献   

Temporal aspects of the VO2 response at the power output associated with VO2peak in well trained cyclists--implications for interval training prescription     

Laursen PB  Shing CM  Jenkins DG 《Research quarterly for exercise and sport》2004,75(4):423-428

The power output achieved at peak oxygen consumption (VO2peak) and the time this power can be maintained (i.e., Tmax) have been used in prescribing high-intensity interval training. In this context, the present study examined temporal aspects of the VO2 response to exercise at the cycling power that output well trained cyclists achieve their VO2peak (i.e., Pmax). Following a progressive exercise test to determine VO2peak, 43 well trained male cyclists (M age = 25 years, SD = 6; M mass = 75 kg, SD = 7; M VO2peak = 64.8 ml x kg(-1) x min(-1), SD = 5.2) performed two Tmax tests 1 week apart. Values expressed for each participant are means and standard deviations of these two tests. Participants achieved a mean VO2peak during the Tmax test after 176 s (SD = 40; M = 74% of Tmax, SD = 12) and maintained it for 66 s (SD = 39; M = 26% of Tmax, SD = 12). Additionally, they obtained mean 95% of VO2peak after 147 s (SD = 31; M = 62% of Tmax, SD = 8) and maintained it for 95 s (SD = 38; M = 38% of Tmax, SD = 8). These results suggest that 60-70% of Tmax is an appropriate exercise duration for a population of well trained cyclists to attain VO2peak during exercise at Pmax. However, due to intraparticipant variability in the temporal aspects of the VO2 response to exercise at Pmax, future research is needed to examine whether individual high-intensity interval training programs for well trained endurance athletes might best be prescribed according to an athlete's individual VO2 response to exercise at Pmax.  相似文献   

Getting on the fast track, or how to get an MLIS through distance education, with a specialization in medical librarianship     

Detlefsen EG 《Medical reference services quarterly》2004,23(4):87-94

The article describes an innovation in MLIS education for medical librarianship, with an introduction to the FastTrack, the distance education program at the University of Pittsburgh's library and information science school, together with an overview of a model program linking the biomedical library at Vanderbilt University with the School of Information Sciences in Pittsburgh. Admissions requirements and specific curriculum for the distance education master's degree are detailed in an FAQ format.  相似文献   

How much effort is needed to keep up with the literature relevant for primary care?     

Brian S Alper  Jason A Hand  Susan G Elliott  Scott Kinkade  Michael J Hauan  Daniel K Onion  Bernard M Sklar 《Journal of the Medical Library Association》2004,92(4):429-437

OBJECTIVES: Medicine must keep current with the research literature, and keeping current requires continuously updating the clinical knowledge base (i.e., references that provide answers to clinical questions). The authors estimated the volume of medical literature potentially relevant to primary care published in a month and the time required for physicians trained in medical epidemiology to evaluate it for updating a clinical knowledge base. METHODS: We included journals listed in five primary care journal review services (ACP Journal Club, DynaMed, Evidence-Based Practice, Journal Watch, and QuickScan Reviews). Finding little overlap, we added the 2001 "Brandon/Hill Selected List of Print Books and Journals for the Small Medical Library." We counted articles (including letters, editorials, and other commentaries) published in March 2002, using bibliographic software where possible and hand counting when necessary. For journals not published in March 2002, we reviewed the nearest issue. Five primary care physicians independently evaluated fifty randomly selected articles and timed the process. RESULTS: The combined list contained 341 currently active journals with 8,265 articles. Adjusting for publication frequency, we estimate 7,287 articles are published monthly in this set of journals. Physicians trained in epidemiology would take an estimated 627.5 hours per month to evaluate these articles. CONCLUSIONS: To provide practicing clinicians with the best current evidence, more comprehensive and systematic literature surveillance efforts are needed.  相似文献   

Grey literature in the life of GESAMP,an international marine scientific advisory body     

Bertrum?H.?MacDonaldEmail author  Ruth?E.?Cordes  Peter?G.?Wells 《Publishing Research Quarterly》2004,20(1):25-41

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