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1.
We analyse the evolution of the slope (critical speed) and the y-intercept (anaerobic distance capacity) of the linear distance-time relationship over a century of Olympic running performances. The distance-time relationship of each Olympic Games (1920-2004) was plotted using the performances in the 800-, 1500- and 5000-m track events. Values for critical speed and anaerobic distance capacity were determined by linear modelling. Mean performances for the 800, 1500 and 5000 m were 104.9 +/- 1.5 s (1.4%), 217.2 +/- 2.8 s (1.3%) and 808.9 +/- 18.4 s (2.3%), respectively. Critical speed improved during the first three-quarters of the twentieth century to reach a plateau in 1984. This is in accordance with the literature (Peronnet & Thibault, 1989) and suggests that "human aerobic endurance" has improved within the century (+13.4%) and tends to stabilize. Anaerobic distance capacity was highly variable over the century (coefficient of variation = 9.4%) and did not show a linear improvement over the years as has previously been suggested (Peronnet & Thibault, 1989). This could be due to an artefact in the application of the two-parameter model to only three Olympic performances. A limitation to the use of this linear mathematical model to fit physiological data may have been demonstrated. 相似文献
2.
This study explores working students' college experiences using the grounded theory approach. Focus groups were conducted to allow working students to elaborate on their college experiences, clarifying issues not easily addressed through surveys. Two theoretical propositions are offered to describe how working students are constantly searching for meaningful work as well as meaning in their work. It is important for institutions to consider work as an educationally purposeful activity outside classroom and to create job opportunities that benefit students academically, socially and financially. 相似文献
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CONSTANTINE A. Papandreou DIONISIS X. Adamopoulos 《Education and Information Technologies》1997,2(3):207-218
This paper examines the influence of multimedia communication services in education and training. After a brief introduction in multimedia communication systems and an analysis of the learning process, a framework for the application of distributed, broadband multimedia communication services in education and training is proposed. Its main elements, which are a set of requirements, a generic layered model and a list of important related matters, are then discussed in considerable detail. Finally, the application of the proposed framework in the field of telecommunications training is suggested 相似文献
5.
Socioeconomic status (SES) and bilingualism have been shown to influence executive functioning during early childhood. Less is known, however, about how the two factors interact within an individual. By analyzing a nationally representative sample of approximately 18,200 children who were tracked from ages 5 to 7 across four waves, both higher SES and bilingualism were found to account for greater performance on the inhibition and shifting aspects of executive functions (EF) and self-regulatory behaviors in classroom. However, only SES reliably predicted verbal working memory. Furthermore, bilingualism moderated the effects of SES by ameliorating the detrimental consequences of low-SES on EF and self-regulatory behaviors. These findings underscore bilingualism's power to enrich executive functioning and self-regulatory behaviors, especially among underprivileged children. 相似文献
6.
Afforestation in China provides carbon sequestration and prevents soil erosion, but its remote impacts on climate in other regions via the coupling of forest energy fluxes with atmospheric circulation are largely unknown. Here, we prescribe inventory-based forest cover change and satellite-observed leaf area index from 1982 to 2011 in a coupled land-atmosphere model to simulate their biophysical climate effects. Both local and global surface air temperatures show a seasonal contrast in response to past vegetation cover expansion over China: a phenomenon we primarily attribute to a variation of seasonality of vegetation greening. A large cooling in spring results in concurrent decreases in geopotential height over China and zonal wind over Mongolia, causing a dipole structure in the upper troposphere over the Arctic. This accounts for ∼58% of simulated spring warming over the Russian Arctic and ∼61% of simulated spring cooling over the Canadian Artic. Our results imply that spring vegetation dynamics in China may affect climate in northern high latitudes. 相似文献
7.
Justin X. Nicoll Andrew J. Galpin Donald B. Thomason Christopher A. Moore 《European Journal of Sport Science》2017,17(9):1194-1202
Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels. 相似文献
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In this study, we examined the effect of string vibration damping devices on reducing racket frame vibration transfer to the forearm. Twenty participants volunteered to hold a tennis racket stationary in a forehand and backhand stroking position while tennis balls were fired at 20 m x s(-1) towards two impact locations, the node of vibration and the dead spot. A three-way analysis of variance with repeated measures on damping condition, impact location and stroke condition was performed on the data. The resonant frequency of the hand-held racket was found to be approximately 120 Hz. No significant differences in amplitude of vibration at the resonant frequency were found for the wrist or the elbow when damped and non-damped impacts were compared. Impacts at the dead spot produced greater amplitudes of vibration (P < 0.01) but no interaction between impact location and string dampers was evident. The string dampers had no effect on the grip force used or the muscle electrical activity in the forearm after impact. In conclusion, we found that string dampers do not reduce the amount of racket frame vibration received at the forearm. We suggest that string dampers remain a popular accessory among tennis players because of their acoustic effects and psychological support rather than any mechanical advantage. 相似文献
10.
对我国学生体质状况的灰色关联聚类分析 总被引:1,自引:0,他引:1
以灰色系统理论中的关联分析方法为基础,建立了基于关联度的聚类分析方法,对1995年全国汉族7~22岁男性学生的体质进行了聚类评价。结果表明:我国大学阶段各年龄组学生群体体质处于最优这一层次;高中阶段各年龄组学生群体体质处于最差层次;初中阶段各年龄组学生群体体质处于中等层次;小学阶段的各年龄组学生群体体质分属于优、中、劣之间。同时显示出,基于灰色关联度聚类的方法计算简捷,结果直观清晰,从而为群体体质的综合评价提供了一种新的量化方法。 相似文献