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Karsten Koehler Hans Braun Markus De Marées Gerhard Fusch Christoph Fusch Joachim Mester 《Journal of sports sciences》2013,31(13):1435-1449
Abstract The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal · day?1). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g · kg?1 · day?1). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal · day?1) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal · min?1; cycling: r = 0.95, SEE = 1.4 kcal · min?1). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes. 相似文献
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Researchers have argued that Twitter has potential to support high-quality professional development (PD) that can respond to teachers’ questions and concerns just in time and “on the spot.” Yet, very little attention has been paid to instances where Twitter has made just-in-time learning possible. In this paper, we examine one instance of timely professional development on Twitter, in which 3,598 users used an educational hashtag—#educattentats—to create a temporary affinity space supporting French teachers preparing to discuss recent terrorist attacks with their students. We describe this just-in-time PD by focusing on participants and modes of participation, the spread of the hashtag in its first hours and the growth and eventual decline of the hashtag over the course of 28 days. The results of this study suggest that #educattentats served effectively as just-in-time professional development for teachers. Implications for research and practice are discussed. 相似文献
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Tianyi Zhang Matthew J. Koehler Alexandru Spatariu 《The American journal of distance education》2013,27(4):194-211
Abstract This study was conducted to develop an inventory that measures students' motivation to engage in critical reasoning in online discussions. Inventory items were developed based on theoretical frameworks and then tested on 168 participants. Using exploratory factor analysis, test–retest reliability, and internal consistency, twenty-two items were selected for the Motivation for Critical Reasoning in Online Discussions Inventory. Six motivational constructs were supported: Interest and Enjoyment, Normative Goals, Outcome Goals, Implicit Theories, Self-Efficacy Perception, and Finishing Requirements. The inventory can be used by other researchers or online instructors to collect students' motivational data to investigate strategies to promote student motivation in online discussions. 相似文献
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Karsten Koehler Neele R. Hoerner Jenna C. Gibbs Christoph Zinner Hans Braun Mary Jane De Souza 《Journal of sports sciences》2016,34(20):1921-1929
Low energy availability, defined as low caloric intake relative to exercise energy expenditure, has been linked to endocrine alterations frequently observed in chronically energy-deficient exercising women. Our goal was to determine the endocrine effects of low energy availability in exercising men. Six exercising men (VO2peak: 49.3 ± 2.4 ml · kg?1 · min?1) underwent two conditions of low energy availability (15 kcal · kg?1 fat-free mass [FFM] · day?1) and two energy-balanced conditions (40 kcal · kg?1 FFM · day?1) in randomised order. During one low energy availability and one balanced condition, participants exercised to expend 15 kcal · kg?1 FFM · day?1; no exercise was conducted during the other two conditions. Metabolic hormones were assessed before and after each 4-day period. Following both low energy availability conditions, leptin (?53% to ?56%) and insulin (?34% to ?38%) were reduced (P < 0.05). Reductions in leptin and insulin were independent of whether low energy availability was attained with or without exercise (P > 0.80). Low energy availability did not significantly impact ghrelin, triiodothyronine, testosterone and IGF-1 (all P > 0.05). The observed reductions in leptin and insulin were in the same magnitude as changes previously reported in sedentary women. Further research is needed to understand why other metabolic hormones are more robust against low energy availability in exercising men than those in sedentary and exercising women. 相似文献
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“Science Talks” in Kindergarten Classrooms: Improving Classroom Practice Through Collaborative Action Research 总被引：1，自引：0，他引：1
Meilan Zhang Susan Passalacqua Mary Lundeberg Matthew J. Koehler Jan Eberhardt Joyce Parker Mark Urban-Lurain Tianyi Zhang Sunhee Paik 《Journal of Science Teacher Education》2010,21(2):161-179
In this study we described an action research project enacted by a veteran Kindergarten teacher (Sarah) in the context of
a professional development program. Over the course of a year, Sarah collaborated with other teachers in a small group to
investigate how to use “Science Talks” to promote student learning in Kindergarten classrooms. A Problem-Based Learning approach
was adopted to guide the collaborative action research. Based on a rich set of data sources, we concluded that Sarah’s action
research improved student learning and led to her own professional growth. We also identified important conditions in support
of action research. 相似文献
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Pamara F. Chang Yoon Hyung Choi Natalya N. Bazarova Corinna E. Löckenhoff 《广播与电子媒介杂志》2015,59(2):221-239
This article extends socioemotional selectivity theory to online social networking by examining age differences in the size and composition of Facebook networks across a wide age range of Facebook users (18 to 93 years old) in a nationally representative sample. Findings suggest increasing selectivity of Facebook social partners with age. Compared to younger adults, friend networks of older adults are smaller but contain a greater proportion of individuals who are considered to be actual friends. Moreover, a higher proportion of actual to total Facebook friends is associated with lower levels of social isolation and loneliness across the life span. 相似文献
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Peggy A. Ertmer Adrie A. Koehler 《Educational technology research and development : ETR & D》2014,62(5):617-636
Case studies hold great potential for engaging students in disciplinary content. However, little is known about the extent to which students actually cover the problem space afforded by a particular case study. In this research, we compared the problem space afforded by an instructional design case study with the actual content covered by 16 graduate students participating in an online case discussion. In addition, we examined prompts used by two instructors to both widen and deepen that coverage. Results showed that 86 % of the afforded problem space was covered during the week-long discussion, although problem-space components were not covered equally. To keep students focused on relevant case details, the instructors used a variety of prompts, accounting for 15 % of the total postings. Implications for research and practice are discussed including ways to use case mapping as both a teaching and analysis tool. 相似文献