It has been suggested that the psychological stress associated with competitive sports events may help to explain the increased susceptibility to respiratory infections due to reductions in secretory immunity. In the current study, we investigated the influence of competitive exercise and psychological stress on secretory immunoglobulin A (s-IgA). Salivary s-IgA and heart rate were measured in 62 healthy young recreationally active men at rest and, in a between-subjects design, following one of four 8-min tasks: mental arithmetic, cycling at workloads of 60 to 180 W (mean = 146 W), mental arithmetic while cycling, or competitive cycling. Mental arithmetic was associated with significant increases in s-IgA concentration (mean = 49 microg.min(-1)) and s-IgA secretion rate (mean = 25 microg.ml(-1)) compared with rest, while mental arithmetic combined with exercise was associated with a significant increase in s-IgA concentration only (mean = 124 microg.min(-1)). In contrast, competitive exercise and exercise alone did not influence s-IgA concentration or secretion rate. Heart rate increased modestly to mental arithmetic (mean = 7 beats.min(-1)) and substantially, and similarly, to the three exercise tasks (mean = 56(62 beats.min(-1)). The hypothesis that the psychological stress of competitive exercise contributes to increased susceptibility to infection via reductions in s-IgA requires further investigation. 相似文献
A four-test short form of the WISC-R was developed on the basis of both rational and statistical criteria, using data from the representative standardization sample. The short-form comprised Arithmetic and Vocabulary from the Verbal Scale along with Picture Arrangement and Block Design from the Performance Scale. Various psychometric properties of the abbreviated battery were defined, and indicators of the short form's accuracy in predicting Full-Scale IQ (the standard error of estimate, effectiveness in classifying a child's intelligence level) were provided. A major topic of discussion was the use and abuse of short forms. 相似文献
Developmental trajectories of personal and collective self-concept were examined among American Indian adolescents. Personal self-concept (self-esteem) and collective self-concept (American Indian identity, Euro-American identity, community-mindedness) were assessed 6 times over 3 years in 4 cohorts of adolescents from 3 American Indian cultural groups (N=1,252). An accelerated longitudinal design was used to estimate developmental trajectories from 14 to 19 years; parallel-process and covariate models were used to examine variation in trajectories. Both personal and collective self-concepts were generally positive and showed small gains; they were moderately related to one another and differentially related to cultural group, gender, and perceived social support. The findings highlight the complexity of self-concept for American Indian youth and the significance of both personal and collective identity. 相似文献
We have previously reported in this journal that spatial ability influences academic performance in engineering. We have also reported that spatial ability is trainable, and can be increased through instruction focused on using perception and mental imagery in three-dimensional representation. In this article, we present the results of a longitudinal evaluative study of student difficulties with engineering graphics at our university, involving research over a 24-year period. Prior to our intervention, the first-year engineering graphics course at our university had a failure rate of 36% for all engineering students, and failure rates of 80% for African students studying at our university. In terms of outcomes, our study indicates that changed teaching practices have been associated with increased pass rates, which currently average 88% for all students. There is clear evidence that African students no longer experience major difficulties in passing the course. This can be attributed both to changes in teaching methodology, as well as broader contextual changes occurring in South Africa over the period reviewed.
Despite evidence of increased pass rates, our data suggest that there is a continuing relationship between three-dimensional spatial perception and academic performance in engineering graphics, as well as with aggregated first-year engineering marks. For this reason, many students still require academic support. There is also evidence that female students experience difficulties with engineering graphics due to lack of previous technical experience, and use a variety of strategies to overcome their study problems. The most effective appear to be use of peers and friends, and in particular students who had previously taken the course, as mediators of the course content and materials. Those female students who have not taken technical drawing at school level, and female students who do not network with other engineering students, are those at greatest disadvantage. 相似文献