Considering cluster analysis in sport medicine and injury prevention research.

OBJECTIVE: In the field of sport medicine and injury prevention in sport, prospective study designs implementing cluster randomization or grouping of subjects by cluster (ie, team, clinic, school, community) are becoming increasingly common. However, there are very few published studies in the field that adequately account for clustering effects in the design and analysis, leading to potentially spurious conclusions. This paper will review the implications of using a cluster RCT or other intervention or observational design grouping individuals by cluster and to highlight the practical implications of appropriate analysis considering the effects of clustering. DATA SOURCES/SYNTHESIS: Previously published papers have provided a foundation of expertise to discuss the often neglected impact of ignoring the effects of cluster in the design and analysis of cluster RCT and other study designs that group individuals by cluster in sport medicine. RESULTS: The loss of statistical efficiency inherent when a study design implements randomization or grouping by cluster is reviewed. Specifically, the effect of cluster design on sample size considerations and analysis are discussed in the context of data from a recently published cluster RCT examining the effectiveness of a balance training prevention strategy in youth basketball. CONCLUSIONS: Researchers in sport medicine are encouraged and challenged to consider appropriate research design and analytical techniques more consistently when study subjects function in the context of a cluster in order to avoid spurious results and misleading conclusions.     

The menstrual cycle and sport performance

The female sex steroid hormones estrogen and progesterone have potential effects on exercise capacity and performance through numerous mechanisms, such as substrate metabolism, cardiorespiratory function, thermoregulation, psychologic factors, and injuries. Consequently, hormone level changes may theoretically lead to either improved or decreased performance at various times throughout the menstrual cycle. Numerous methodological issues and a paucity of studies have precluded evidence-based conclusions in almost every area of research in this field. In addition, there appears to be a great degree of inter- and intraindividual variability in these hormonal responses. Using oral contraceptives may be advantageous for female athletes who are negatively affected by their menstrual cycle, as they may provide a stable yet controllable hormonal milieu for training and competition.     

The application of mental fatigue research to elite team sport performance: New perspectives

ObjectivesMental fatigue resulting from prolonged periods of demanding cognitive activity, has been found to impair endurance exercise performance and performance in some sport-specific tasks. The application of such research to the elite sporting environment however is limited.Design & MethodsThis article reviews the literature relevant to mental fatigue and team sporting performance with aim to provide perspectives on the transferability and significance of currently available evidence to the applied elite sporting context.ResultsInconsistent findings in the limited available literature can be attributed to large variations in the participants involved, the nature of the cognitively demanding tasks used to induce mental fatigue and the tests used to assess performance outcomes. Few studies have used trained athletes in combination with performance tests that accurately represent the physiological and technical demands experienced by athletes in competition. While there is growing interest in the acute influence of mental fatigue on exercise performance, a potential cumulative effect of mental fatigue on performance over, for example, a competitive season is an area yet to be investigated.ConclusionsIf it is accepted that mental fatigue impairs the performance of some athletes, then improving the ecological validity of research in the area of mental fatigue and sport will significantly advance our understanding of how to better monitor and manage mental fatigue. At the elite level of competition, where outcomes are determined by very small margins of difference, reducing the impact of mental fatigue on performance has potential to be significant.     

Physiological and anthropometric determinants of sport climbing performance

OBJECTIVE: To identify the physiological and anthropometric determinants of sport climbing performance. METHODS: Forty four climbers (24 men, 20 women) of various skill levels (self reported rating 5.6-5.13c on the Yosemite decimal scale) and years of experience (0.10-44 years) served as subjects. They climbed two routes on separate days to assess climbing performance. The routes (11 and 30 m in distance) were set on two artificial climbing walls and were designed to become progressively more difficult from start to finish. Performance was scored according to the system used in sport climbing competitions where each successive handhold increases by one in point value. Results from each route were combined for a total climbing performance score. Measured variables for each subject included anthropometric (height, weight, leg length, arm span, % body fat), demographic (self reported climbing rating, years of climbing experience, weekly hours of training), and physiological (knee and shoulder extension, knee flexion, grip, and finger pincer strength, bent arm hang, grip endurance, hip and shoulder flexibility, and upper and lower body anaerobic power). These variables were combined into components using a principal components analysis procedure. These components were then used in a simultaneous multiple regression procedure to determine which components best explain the variance in sport rock climbing performance. RESULTS: The principal components analysis procedure extracted three components. These were labelled training, anthropometric, and flexibility on the basis of the measured variables that were the most influential in forming each component. The results of the multiple regression procedure indicated that the training component uniquely explained 58.9% of the total variance in climbing performance. The anthropometric and flexibility components explained 0.3% and 1.8% of the total variance in climbing performance respectively. CONCLUSIONS: The variance in climbing performance can be explained by a component consisting of trainable variables. More importantly, the findings do not support the belief that a climber must necessarily possess specific anthropometric characteristics to excel in sport rock climbing.     

Dynamic performance assessment of selected sport shoes on impact forces

Few investigators have evaluated the performance characteristics of non-running sport shoes. The purpose of this study was to assess the dynamic performance characteristics of four different shoe models during landings. Five male subjects performed 25 voluntary hanging drop landings (60 cm) onto a force platform (1000 Hz) for each of four shoe conditions (C1 and C2 = basketball shoe, C3 = running shoe, C4 = volleyball shoe). Ground reaction force data were evaluated for maximum forefoot (F1) and rearfoot (F2) impact forces as well as the respective times of occurrence of these events (T1, T2). Results of the group data analysis indicated a preferential performance rank order of C1, C3, C4, C2 although significant interaction effects were observed, indicating a need for single-subject analyses. Three techniques were incorporated to assess individual subject condition differences, all of which elicited unique rank orders for the shoes although each identified C1 as the "best" shoe condition. The results of the study support the necessity for within-subject analyses conducted with an adequate number of trials when attempting to detect subtle performance differences that may exist between various sport shoes. Whether the observed statistically significant differences are biomechanically meaningful remains an important unanswered question.     

The role of genetic research in sport

Aims

This study describes the history of the application of genetics in sport and present achievements in this field.

News

It reviews the main directions in genetics with regard to sport: population genetics, popular in the second half of the 20th century, based on studies of the phenotypic characteristics without genotype pattern recognition; the beginnings of research on genotype characteristics with genotype pattern recognition; and recent achievements in molecular biology after the completion of ‘The Human Genome Project’ in 2003. The first section of the paper presents the significance, role and the most important achievements of early genetic researches based on the comparison of twins and parents with children. Thus developed heritability indices for individual traits are still a very precious source of information for people responsible for planning training. The next part of the paper presents a gradual development of molecular research in sport. The analysis concerned the first of a few dozen currently examined genetic markers (ACE, ACTN3, MSTN) and genetic conditions of individual functional traits of the human body, with the emphasis on the potential application of this knowledge. We also present the increasing ethical concerns with regard to the use of molecular techniques in sport and related threats, such as the use of the genetic doping in sport. The last part of the paper attempts to determine the role and range of genetics in sport in the future, for example in traumatology, rehabilitation, and sport medicine.     

Treatment of acute combined knee instabilities and subsequent sport performance

Severe knee ligament injuries have ruined many sport careers, but this may be prevented by appropriate treatment. A short review of the treatment of combined knee instabilities is presented and illustrated by four clinical cases involving skiing racers on the Norwegian alpine and free-style World Cup teams. All of them went back to racing after surgical treatment. One improved, one regained and one partially regained their preinjury World Cup standings. The fourth racer suffered from arthrofibrosis postoperatively. The was unable to carry through a full racing season after rehabilitation due to a new injury. The mean World Cup rankings of the racers was 24 before compared with 14.6 after the injury. In conclusion, it is possible to continue ski racing at the top level even after severe knee injuries.