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Changes in muscle activity with increasing running speed 总被引：3，自引：2，他引：1
Electromyographic (EMG) activity of the leg muscles and the ground reaction forces were recorded in 17 elite male middle-distance runners, who performed isometric maximal voluntary contractions (MVC) as well as running at different speeds. Electromyograms were recorded from the gluteus maximus, vastus lateralis, biceps femoris, gastrocnemius and tibialis anterior. The results indicated that the averaged EMG (aEMG) activities of all the muscles studied increased (P < 0.05) with increasing running speed, especially in the pre-contact and braking phases. At higher speeds, the aEMG activities of the gastrocnemius, vastus lateralis, biceps femoris and gluteus maximus exceeded 100% MVC in these same phases. These results suggest that maximal voluntary contractions cannot be used as an indicator of the full activation potential of human skeletal muscle. Furthermore, the present results suggest that increased pre-contact EMG potentiates the functional role of stretch reflexes, which subsequently increases tendomuscular stiffness and enhances force production in the braking and/or propulsive phases in running. Furthermore, a more powerful force production in the optimal direction for increasing running speed effectively requires increased EMG activity of the two-joint muscles (biceps femoris, rectus femoris and gastrocnemius) during the entire running cycle. 相似文献
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Teemu?P??kk?nen Jaana?Kek?l?inenEmail author Heikki?Keskustalo Leif?Azzopardi David?Maxwell Kalervo?J?rvelin 《Information Retrieval》2017,20(4):338-362
A searcher’s interaction with a retrieval system consists of actions such as query formulation, search result list interaction and document interaction. The simulation of searcher interaction has recently gained momentum in the analysis and evaluation of interactive information retrieval (IIR). However, a key issue that has not yet been adequately addressed is the validity of such IIR simulations and whether they reliably predict the performance obtained by a searcher across the session. The aim of this paper is to determine the validity of the common interaction model (CIM) typically used for simulating multi-query sessions. We focus on search result interactions, i.e., inspecting snippets, examining documents and deciding when to stop examining the results of a single query, or when to stop the whole session. To this end, we run a series of simulations grounded by real world behavioral data to show how accurate and responsive the model is to various experimental conditions under which the data were produced. We then validate on a second real world data set derived under similar experimental conditions. We seek to predict cumulated gain across the session. We find that the interaction model with a query-level stopping strategy based on consecutive non-relevant snippets leads to the highest prediction accuracy, and lowest deviation from ground truth, around 9 to 15% depending on the experimental conditions. To our knowledge, the present study is the first validation effort of the CIM that shows that the model’s acceptance and use is justified within IIR evaluations. We also identify and discuss ways to further improve the CIM and its behavioral parameters for more accurate simulations. 相似文献
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Ronimus Miia Eklund Kenneth Pesu Laura Lyytinen Heikki 《Educational technology research and development : ETR & D》2019,67(3):639-663
Educational technology research and development - This study investigates the effectiveness of a digital game—GraphoLearn (GL)—in supporting second-grade students who have persistent... 相似文献
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Leinonen Seija Müller Kurt Leppänen Paavo H.T. Aro Mikko Ahonen Timo Lyytinen Heikki 《Reading and writing》2001,14(3-4):265-296
Subgroups of Finnish dyslexic adults (N = 84)displaying, relative to each other, a distinctivecombination of accuracy and speed of oral text readingwere compared in phonological and orthographicprocessing, verbal short-term memory and readinghabits. Inaccurate phonological decoding appeared todetermine the number of errors made in text reading,while inability to utilize effectively rapid lexicalaccess of words manifested as slow text reading speed.Phonological and orthographic word recognitionprocesses were less tightly integrated among dyslexicthan normal readers. Our results indicate thatadvanced orthographic processing skills might help anumber of the dyslexic readers to compensate for theirserious phonological deficits. The subgroups alsodiffered from each other in reading habits. Arelatively fast reading speed, even with numerouserrors, appears to be more rewarding in everydayreading than a slower but more accurate readingstyle. 相似文献
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The purpose of this study was to construct and study the impact of a research‐based sequence for teaching the concept of modelling to seventh‐grade science students. We identified students' notions of models and the aspects of school science to be addressed regarding the model concept, which were then taken into account when we planned the learning sequence. The idea of modelling in science was taught while the students were learning about the change of states of matter in seventh‐grade physics. A pre‐interview revealed that the students' notions of models were very limited, while a post‐interview showed that this improved in the course of the series of lessons. There was also a statistically significant difference in the students' understanding of modelling between our target group and a control group consisting of ninth‐grade students who had received only the normal teaching. However, a delayed post‐questionnaire completed a few months after the teaching sequence showed that the stability of learning results were dependent on whether models and modelling were used in the normal teaching conducted after the teaching sequence. Implications for teaching, teacher education and research are also addressed in this paper. 相似文献
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In this article, we examine content supply as a public service strategy in Finland, one of the forerunner countries of digital terrestrial television in Europe. Regarding digitalization, European broadcasters face several options from full service to a specialized mission. The case at hand is the first full digital year of 2002 in Finland. The focus is on one of the traditional principles of public service broadcasting, the diversity of programming, as it is realized in the new, digital, multichannel environment. We examine content diversity by comparing channel profiles as well by analyzing indexes of the horizontal and vertical breadth and dissimilarity of programming. In a market of two public service and two commercial analogue generalist TV channels, the five new thematic digital channels have radically altered the amount of system-wide supply, but the diversity of programming has not suffered. This is due to the specializing strategy of the public service broadcaster. Its approach to focus on factual programming is clear in its digital output but can be detected in moderation also in its analogue supply. However, with the expected increase on commercial digital supply also in terrestrial networks, there is the possibility of the generalist public service broadcaster to turn into a fragmented one. 相似文献
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Jarkko Mylläri Heikki Kynäslahti Olli Vesterinen Sanna Vahtivuori-Hänninen Lasse Lipponen Seppo Tella 《Scandinavian Journal of Educational Research》2013,57(5):537-550
This article discusses students' pedagogical thinking in situations where the use of information and communication technologies (ICTs) has a (well-defined) pedagogical role and rationale. By analysing students' pedagogical thinking in this setting, it is also possible to better understand their motivations and self-regulation. Pedagogical thinking as viewed from the student's angle is a new area of educational research. Our research method is a combination of the Stimulated Recall interview and the semi-structured theme interview. In addition, some background data were gathered by questionnaire to discern students' different uses of ICTs and their contexts. The findings suggest how the educational use of ICTs is considered to be meaningful and motivating by both genders and among all the interviewed age groups, in spite of the fact that an acute and vocal critique seems to develop among older students. The differences reside in students' reasoning regarding decision making in task operations between genders, which was one of the background variables—girls actively include identity and opinion, while boys emphasize the quality of performance as motives for decisions. 相似文献
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Sini Huemer Mikko Aro Karin Landerl Heikki Lyytinen 《Scientific Studies of Reading》2013,17(4):317-340
The study evaluated the effect of repeated reading on reading speed among 36 Finnish-speaking poor readers in Grades 4 to 6. A switching replications design was applied: Group A (n = 20) received training first, and during this period Group B (n = 16) acted as a control group. After a midpoint test, the design was switched. The training material consisted of syllables, which were practiced during 10 training sessions for a total of 50 times. The reading speed of the trained syllables increased more during training than during the control period. During training, the reading speed of pseudowords containing the trained syllables improved significantly. This improvement was found both in a computer task and in a list-reading task, which had a lower congruency with the training method than the computer task. Finally, training did not induce changes in a control (text reading) task that assessed general reading speed. 相似文献