Effects of cigarette smoking on cardiac autonomic function during dynamic exercise     

Mendonca GV  Pereira FD  Fernhall B 《Journal of sports sciences》2011,29(9):879-886

The purpose of this study was to investigate the acute effect of cigarette smoking on cardiac autonomic function in young adult smokers during dynamic exercise. Fourteen healthy young smokers (21.4 ± 3.4 years) performed peak and submaximal exercise protocols under control and smoking conditions. Resting and submaximal beat-to-beat R-R series were recorded and spectrally decomposed using the fast Fourier transformation. Smoking resulted in a significant decrease in work time, VO(2peak) and peak O(2) pulse (P < 0.05). Heart rate increased at rest and during submaximal exercise after smoking (P < 0.05). The raw high frequency and low frequency power were significantly reduced by smoking, both at rest and during exercise (P < 0.05). The low to high frequency ratio was higher after smoking (P < 0.05). The normalised low frequency power was also significantly increased by smoking, but only at rest (P < 0.05). These data demonstrate that the tachycardic effect elicited by smoking is accompanied by acute changes in heart rate spectral components both at rest and during exercise. Therefore, the cardiac autonomic control is altered by smoking not only at rest, but also during exercise, resulting in reduced vagal modulation and increased sympathetic dominance.  相似文献   

Validity and reliability of a new field test (Carminatti's test) for soccer players compared with laboratory-based measures     

Da Silva JF  Guglielmo LG  Carminatti LJ  De Oliveira FR  Dittrich N  Paton CD 《Journal of sports sciences》2011,29(15):1621-1628

The aim of this study was to assess the validity (Study 1) and reliability (Study 2) of a novel intermittent running test (Carminatti's test) for physiological assessment of soccer players. In Study 1, 28 players performed Carminatti's test, a repeated sprint ability test, and an intermittent treadmill test. In Study 2, 24 players performed Carminatti's test twice within 72 h to determine test-retest reliability. Carminatti's test required the participants to complete repeated bouts of 5 × 12 s shuttle running at progressively faster speeds until volitional exhaustion. The 12 s bouts were separated by 6 s recovery periods, making each stage 90 s in duration. The initial running distance was set at 15 m and was increased by 1 m at each stage (90 s). The repeated sprint ability test required the participants to perform 7 × 34.2 m maximal effort sprints separated by 25 s recovery. During the intermittent treadmill test, the initial velocity of 9.0 km · h(-1) was increased by 1.2 km · h(-1) every 3 min until volitional exhaustion. No significant difference (P > 0.05) was observed between Carminatti's test peak running velocity and speed at VO(2max) (v-VO(2max)). Peak running velocity in Carminatti's test was strongly correlated with v-VO(2max) (r = 0.74, P < 0.01), and highly associated with velocity at the onset of blood lactate accumulation (r = 0.63, P < 0.01). Mean sprint time was strongly associated with peak running velocity in Carminatti's test (r = -0.71, P < 0.01). The intraclass correlation was 0.94 with a coefficient of variation of 1.4%. In conclusion, Carminatti's test appears to be avalid and reliable measure of physical fitness and of the ability to perform intermittent high-intensity exercise in soccer players.  相似文献   

Multi-Agent Architecture for Intelligent Tutoring Systems     

Ana Lilia Laureano–Cruces  Fernando De Arriaga–Gómez 《Interactive Learning Environments》2013,21(3):225-250

This paper shows a multi-agent architecture based on reactive agents for an intelligent tutoring system (ITS). The global system behavior is modeled taking into account the mental models and the cognitive task analysis. We present the basic characteristics of the reactive system in terms of reactive robotics, where they started. Next we introduce some definitions and schemes in order to characterize the multi-agent architecture. Finally, we present an ITS example called Makatsiná Makatsiná means tutor in TOTONACA, a Mexican pre-Spanish language. which teaches the skills necessary to solve a truss analysis problem by the joint method. This domain is an integration skill.  相似文献   

Measuring Inequality of Opportunity in Education by Combining Information on Coverage and Achievement in PISA     

Luis Fernando Gamboa  Fábio D. Waltenberg 《Educational Assessment》2013,18(4):320-337

Measuring the distance between countries and the goal of equality of opportunity in education has been the focus of recent contributions in the economic literature, which have concentrated either on intergroup gaps in access to a given level of studies or on intergroup gaps in educational achievement. We argue that both aspects are important and interrelated and, as a consequence, should be measured simultaneously and combined in a composite index of equality of opportunity in education. Employing recent PISA data for a selected set of countries, rank reversals are observed with respect to orderings based upon a single dimension. The index can be generalized to include further dimensions, such as average scores or dissimilarity in access.  相似文献   

Construction and validation of a psychometric scale to assess extension agents’ beliefs about extension and innovation     

Fernando Landini  Maite Beramendi 《The Journal of Agricultural Education and Extension》2013,19(5):381-399

ABSTRACT