Neuromuscular, metabolic and hormonal profiles of young tennis players and untrained boys

This study compared the neuromuscular, metabolic and hormonal profiles of trained prepubescent tennis players and an untrained group. The boys in the experimental group (n = 9; mean age +/- S.D. = 11.4 +/- 0.5 years) had participated in tennis training for 2.3 +/- 1.0 years and the boys in the control group (n = 9; mean age +/- S.D. = 10.9 +/- 0.4 years) were normal active volunteers. The tennis players were found to be physically more active than the controls when the comparison was made for either 1 year (4.9 +/- 1.8 vs 2.6 +/- 2.5 times per week; P less than 0.05) or for 1 week (3.4 +/- 1.2 vs 0.4 +/- 0.5 times; P less than 0.001) preceding the tests. Choice reaction time was significantly (P less than 0.01) shorter in the experimental group (258 +/- 16 ms) than in the control group (344 +/- 81 ms). Dropping height in the best drop jump was significantly (P less than 0.05) higher in the tennis players (0.46 +/- 0.19 m) than in the control boys (0.27 +/- 0.10 m). The tennis players had significantly lower oxygen consumption at the 'anaerobic threshold' than the controls (P less than 0.05). There were no significant differences between the groups in serum hormone levels. The small differences that existed may have been caused by active participation in sport by the tennis players.     

Establishing reliability of biomechanical data using univariate and multivariate approaches

The purpose of this study was to use generalizability theory with both univariate and multivariate approaches to examine reliability of total body center of mass (CM) values calculated from cinematographical data. Twenty-eight college-aged male volunteers were filmed by a LOCAM camera at 100 fps while performing the basic locomotion skill of walking. Film analysis was conducted on each subject using six frames of film depicting a one-stride walking cycle consisting of right heel strike, right foot flat, left toe-off, left heel strike, left foot flat, and right toe-off. Nineteen segmental endpoints and a reference point were digitized by three experienced plotters. The digitizing sequence was replicated three times by each plotter. A FORTRAN program calculated nine CM values (three plotters by three repetitions) for each subject filmed in each of the six positions of the stride. The x- and y-coordinates of the CM values were the dependent variables analyzed by fully crossed 3-way univariate and multivariate ANOVAs (subjects by plotters by repetitions). All measurement facets were considered to be random. Results indicate that there was very little repetition error but considerable interplotter error for most frames. Phi-coefficients for x- and y-coordinates, separately, fluctuated across frames. The univariate values for the x-coordinates were similar but slightly less than the multivariate values. The Phi-coefficients for Y, however, were considerably lower than the multivariate values. The multivariate Phi-coefficients for generalizing over three plotters and three repetitions ranged from .82 to .90.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stress and cognitive functioning in sport

This paper considers the relationship between stress and cognitive functioning and discusses some of the concepts and methods that may be adopted to examine the relationship between stress and sports performance. It considers only that literature that may be relevant to, or furthers, the understanding of sports performance under competitive stress. One of the most popular approaches has been to explain the relationship in terms of the unidimensional inverted-U hypothesis. The validity of this approach to explaining sports performances in specific situations is discussed and it is generally concluded that the inverted-U hypothesis is too vague and simplistic. The discussion considers multidimensional approaches and discusses the suitability and implications of some more recent and more complex models of stress and performance which are now available in the psychological literature. It is concluded that the relationship between stress and sports performance is an extremely complex one and involves the interaction between the nature of the stressor, the cognitive demands of the task being performed and the psychological characteristics of the individuals performing it.