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.     

Cardiovascular and ventilatory responses during formalized T'ai Chi Chuan exercise

T'ai Chi Chuan (TCC) is a widely practiced Chinese martial art said to physically develop balance and coordination as well as enhance emotional and mental health. TCC consists of a series of postures combined into a sequential movement providing a smooth, continuous, low-intensity activity. The purpose of this study was to examine the ventilatory and cardiovascular responses to the Long Form of Yang's style TCC. In addition, the subjects' TCC responses were compared to their ventilatory and cardiovascular responses during cycle ergometry at an oxygen consumption (VO2) equivalent to the mean TCC VO2. Six experienced (M = 8.3 yrs) male TCC practitioners served as subjects with data collected during the Cloud H and movement of the TCC exercise. Significantly (p less than .05) lower responses for ventilatory frequency (Vf) (11.3 and 15.7 breaths.min-1), ventilatory equivalent (VE/VO2) (23.47 and 27.41), and the ratio of dead space ventilation to tidal volume (VD/VT) (20 and 27%) were found in TCC in comparison to cycle ergometry. The percentage of minute ventilation used for alveolar ventilation was significantly higher during TCC (p less than .03) than cycle ergometry, with mean values of 81.1% and 73.1%, respectively. Cardiac output, stroke volume, and heart rate were not significantly different between TCC exercise and cycle ergometry at the same oxygen consumption. We concluded that, during TCC, expert practitioners show significantly different ventilatory responses leading to more efficient use of the ventilatory volume than would be expected from comparable levels of exertion on a cycle ergometer.