Differences in activation patterns between eccentric and concentric quadriceps contractions.     

Malachy P McHugh  Timothy F Tyler  Scott C Greenberg  Gilbert W Gleim 《Journal of sports sciences》2002,20(2):83-91

Previous studies analysing electromyograms (EMGs) from indwelling electrodes have indicated that fast-twitch motor units are selectively recruited for low-intensity eccentric contractions. The aim of this study was to compare the frequency content of surface EMGs from quadriceps muscles during eccentric and concentric contractions at various contraction intensities. Electromyograms were recorded from the rectus femoris, vastus lateralis and vastus medialis muscles of 10 men during isokinetic (1.05 rad x s(-1)) eccentric and concentric knee extension contractions at 25%, 50%, 75% and 100% of maximal voluntary contraction (MVC) for each contraction mode. Additionally, isometric contractions (70 degrees) were performed at each intensity. The mean frequency and root mean square (RMS) of the surface EMG were computed. Mean frequency was higher for eccentric than concentric contractions at 25% (P < 0.01), 50% (P < 0.01) and 75% (P < 0.05) but not at 100% MVC. It increased with increasing contraction intensity for isometric (P < 0.001) and concentric (P < 0.01) contractions but not for eccentric contractions (P = 0.27). The EMG amplitude (RMS) increased with increasing contraction intensity similarly in each contraction mode (P < 0.0001). Higher mean frequencies for eccentric than concentric contractions at submaximal contraction intensities is consistent with more fast-twitch motor units being active during eccentric contractions.  相似文献   

Motion analysis of match-play in elite U12 to U16 age-group soccer players     

Harley JA  Barnes CA  Portas M  Lovell R  Barrett S  Paul D  Weston M 《Journal of sports sciences》2010,28(13):1391-1397

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Shiloh in Fiction     

Timothy Morris 《Journal of American culture (Malden, Mass. : 2003)》2008,31(3):283-292

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Rethinking fat as a fuel for endurance exercise     

Jeff S. Volek  Timothy Noakes  Stephen D. Phinney 《European Journal of Sport Science》2015,15(1):13-20

Abstract

A key element contributing to deteriorating exercise capacity during physically demanding sport appears to be reduced carbohydrate availability coupled with an inability to effectively utilize alternative lipid fuel sources. Paradoxically, cognitive and physical decline associated with glycogen depletion occurs in the presence of an over-abundance of fuel stored as body fat that the athlete is apparently unable to access effectively. Current fuelling tactics that emphasize high-carbohydrate intakes before and during exercise inhibit fat utilization. The most efficient approach to accelerate the body’s ability to oxidize fat is to lower dietary carbohydrate intake to a level that results in nutritional ketosis (i.e., circulating ketone levels >0.5 mmol/L) while increasing fat intake for a period of several weeks. The coordinated set of metabolic adaptations that ensures proper interorgan fuel supply in the face of low-carbohydrate availability is referred to as keto-adaptation. Beyond simply providing a stable source of fuel for the brain, the major circulating ketone body, beta-hydroxybutyrate, has recently been shown to act as a signalling molecule capable of altering gene expression, eliciting complementary effects of keto-adaptation that could extend human physical and mental performance beyond current expectation. In this paper, we review these new findings and propose that the shift to fatty acids and ketones as primary fuels when dietary carbohydrate is restricted could be of benefit for some athletes.  相似文献   

The Undergraduate Research Student Self-Assessment (URSSA): Validation for Use in Program Evaluation     

Timothy J. Weston  Sandra L. Laursen 《CBE life sciences education》2015,14(3)

This article examines the validity of the Undergraduate Research Student Self-Assessment (URSSA), a survey used to evaluate undergraduate research (UR) programs. The underlying structure of the survey was assessed with confirmatory factor analysis; also examined were correlations between different average scores, score reliability, and matches between numerical and textual item responses. The study found that four components of the survey represent separate but related constructs for cognitive skills and affective learning gains derived from the UR experience. Average scores from item blocks formed reliable but moderate to highly correlated composite measures. Additionally, some questions about student learning gains (meant to assess individual learning) correlated to ratings of satisfaction with external aspects of the research experience. The pattern of correlation among individual items suggests that items asking students to rate external aspects of their environment were more like satisfaction ratings than items that directly ask about student skills attainment. Finally, survey items asking about student aspirations to attend graduate school in science reflected inflated estimates of the proportions of students who had actually decided on graduate education after their UR experiences. Recommendations for revisions to the survey include clarified item wording and increasing discrimination between item blocks through reorganization.Undergraduate research (UR) experiences have long been an important component of science education at universities and colleges but have received greater attention in recent years, as they have been identified as important ways to strengthen preparation for advanced study and work in the science fields, especially among students from underrepresented minority groups (Tsui, 2007 ; Kuh, 2008 ). UR internships provide students with the opportunity to conduct authentic research in laboratories with scientist mentors, as students help design projects, gather and analyze data, and write up and present findings (Laursen et al., 2010 ). The promised benefits of UR experiences include both increased skills and greater familiarity with how science is practiced (Russell et al., 2007 ). While students learn the basics of scientific methods and laboratory skills, they are also exposed to the culture and norms of science (Carlone and Johnson, 2007 ; Hunter et al., 2007 ; Lopatto, 2010 ). Students learn about the day-to-day world of practicing science and are introduced to how scientists design studies, collect and analyze data, and communicate their research. After participating in UR, students may make more informed decisions about their future, and some may be more likely to decide to pursue graduate education in science, technology, engineering, and mathematics (STEM) disciplines (Bauer and Bennett, 2003 ; Russell et al., 2007 ; Eagan et al. 2013 ).While UR experiences potentially have many benefits for undergraduate students, assessing these benefits is challenging (Laursen, 2015 ). Large-scale research-based evaluation of the effects of UR is limited by a range of methodological problems (Eagan et al., 2013 ). True experimental studies are almost impossible to implement, since random assignment of students into UR programs is both logistically and ethically impractical, while many simple comparisons between UR and non-UR groups of students suffer from noncomparable groups and limited generalizability (Maton and Hrabowski, 2004 ). Survey studies often rely on poorly developed measures and use nonrepresentative samples, and large-scale survey research usually requires complex statistical models to control for student self-selection into UR programs (Eagan et al., 2013 ). For smaller-scale program evaluation, evaluators also encounter a number of measurement problems. Because of the wide range of disciplines, research topics, and methods, common standardized tests assessing laboratory skills and understandings across these disciplines are difficult to find. While faculty at individual sites may directly assess products, presentations, and behavior using authentic assessments such as portfolios, rubrics, and performance assessments, these assessments can be time-consuming and not easily comparable with similar efforts at other laboratories (Stokking et al., 2004 ; Kuh et al., 2014 ). Additionally, the affective outcomes of UR are not readily tapped by direct academic assessment, as many of the benefits found for students in UR, such as motivation, enculturation, and self-efficacy, are not measured by tests or other assessments (Carlone and Johnson, 2007 ). Other instruments for assessing UR outcomes, such as Lopatto’s SURE (Lopatto, 2010 ), focus on these affective outcomes rather than direct assessments of skills and cognitive gains.The size of most UR programs also makes assessment difficult. Research Experiences for Undergraduates (REUs), one mechanism by which UR programs may be organized within an institution, are funded by the National Science Foundation (NSF), but unlike many other educational programs at NSF (e.g., TUES) that require fully funded evaluations with multiple sources of evidence (Frechtling, 2010 ), REUs are generally so small that they cannot typically support this type of evaluation unless multiple programs pool their resources to provide adequate assessment. Informal UR experiences, offered to students by individual faculty within their own laboratories, are often more common but are typically not coordinated across departments or institutions or accountable to a central office or agency for assessment. Partly toward this end, the Undergraduate Research Student Self-Assessment (URSSA) was developed as a common assessment instrument that can be compared across multiple UR sites within or across institutions. It is meant to be used as one source of assessment information about UR sites and their students.The current research examines the validity of the URSSA in the context of its use as a self-report survey for UR programs and laboratories. Because the survey has been taken by more than 3400 students, we can test some aspects of how the survey is structured and how it functions. Assessing the validity of the URSSA for its intended use is a process of testing hypotheses about how well the survey represents its intended content. This ongoing process (Messick, 1993 ; Kane, 2001 ) involves gathering evidence from a range of sources to learn whether validity claims are supported by evidence and whether the survey results can be used confidently in specific contexts. For the URSSA, our method of inquiry focuses on how the survey is used to assess consortia of REU sites. In this context, survey results are used for quality assurance and comparisons of average ratings over years and as general indicators of program success in encouraging students to pursue graduate science education and scientific careers. Our research questions focus on the meaning and reliability of “core indicators” used to track self-reported learning gains in four areas and the ability of numerical items to capture student aspirations for future plans to attend graduate school in the sciences.  相似文献   

Breaking the Cycle: Future Faculty Begin Teaching with Learner-Centered Strategies after Professional Development     

Diane Ebert-May  Terry L. Derting  Timothy P. Henkel  Jessica Middlemis Maher  Jennifer L. Momsen  Bryan Arnold  Heather A. Passmore 《CBE life sciences education》2015,14(2)

The availability of reliable evidence for teaching practices after professional development is limited across science, technology, engineering, and mathematics disciplines, making the identification of professional development “best practices” and effective models for change difficult. We aimed to determine the extent to which postdoctoral fellows (i.e., future biology faculty) believed in and implemented evidence-based pedagogies after completion of a 2-yr professional development program, Faculty Institutes for Reforming Science Teaching (FIRST IV). Postdocs (PDs) attended a 2-yr training program during which they completed self-report assessments of their beliefs about teaching and gains in pedagogical knowledge and experience, and they provided copies of class assessments and video recordings of their teaching. The PDs reported greater use of learner-centered compared with teacher-centered strategies. These data were consistent with the results of expert reviews of teaching videos. The majority of PDs (86%) received video ratings that documented active engagement of students and implementation of learner-centered classrooms. Despite practice of higher-level cognition in class sessions, the items used by the PDs on their assessments of learning focused on lower-level cognitive skills. We attributed the high success of the FIRST IV program to our focus on inexperienced teachers, an iterative process of teaching practice and reflection, and development of and teaching a full course.  相似文献   

How Custom Agents Really Detect Lies     

Timothy R. Levine  Yasuhiro Daiku 《Communication Research Reports》2019,36(1):84-92

Research has found discrepancies among folk beliefs about lie detection, deception cue utility, and retrospective accounts of detected lies. Elite customs agents (N = 37) were surveyed regarding their overall beliefs about how to detect lies (general strategy), their opinions about best practices (best strategy), and about a successfully detected lie (actual strategy). Responses were coded in three nonexclusive broad categories: (a) behavioral cues, (b) communication content and evidence, and (c) interactive-questioning approaches. Behavioral cues, especially nonverbal cues, were listed most frequently as general beliefs. Opinions about the best approach were evenly split across the three categories. Communication content and evidence was the most frequently reported actual detection method and was mentioned in 97% of the responses. The results are discussed in relation to Truth-Default Theory and their implications for lie detection practice.  相似文献   

The power and politics of international comparisons     

Angeline M. Barrett  Michael Crossley 《Compare》2015,45(3):467-470

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INTERNAL FACTOR STRUCTURE AND CONVERGENT VALIDITY EVIDENCE: THE SELF‐REPORT VERSION OF SELF‐REGULATION STRATEGY INVENTORY     

Timothy J. Cleary  Leah Dembitzer  Ryan J. Kettler 《Psychology in the schools》2015,52(9):829-844

Using a sample of 348 middle school students, we gathered evidence regarding the internal consistency of scores, as well as the internal factor structure and convergent validity evidence for inferences from a self‐report questionnaire called the Self‐Regulation Strategy Inventory–Self Report. Confirmatory factor analysis revealed that the fit indexes for a hierarchical model (composite, three factors) and a single‐level, three‐factor model were highly similar but mixed. Respecification of the hierarchical model based on conceptual overlap of items led to substantial improvement in the overall fit of the model, as indicated by the root mean square error of approximation, chi‐square/df, and the comparative fit index. Correlational analyses also provided strong convergent validity evidence, as the three subscales exhibited statistically significant relations with four motivation beliefs (i.e., self‐efficacy, perceived instrumentality, task interest, perceived responsibility) and two distinct markers of regulation‐related behaviors (i.e., teacher ratings, office discipline referrals).  相似文献   

A Critical Discourse Analysis of No Promo Homo Policies in US Schools     

Brian Barrett  Arron M. Bound 《Educational Studies A Journal of the American Educational Studies Association》2015,51(4):267-283

This article presents a critical discourse analysis of no promo homo policies and their effects in US schools. No promo homo—short for “no promotion of homosexuality” (Eskridge, 2000 Eskridge, W.N. (2000). No promo homo: The sedimentation of antigay discourse and the channeling effect of judicial review. New York Law Review, 75, 1327–1411.[Web of Science ®] , [Google Scholar], p. 1329)—polices have been adopted across nine states and several local school districts in the United States. They direct teachers and school officials to take a neutral position on the subject of sexual orientation and identity and often restrict or prohibit any school-based instruction, counseling, discussion, or activity that could be construed as being positive about or promoting homosexuality (Bonauto, n.d.; Cahill &; Cianciotto, 2004 Cahill, S., &; Cianciotto, J. (2004). US policy interventions that can make schools safer. Journal of Gay &; Lesbian Issues in Education, 2, 3–17.[Taylor &; Francis Online] , [Google Scholar]; Eskridge 2000 Eskridge, W.N. (2000). No promo homo: The sedimentation of antigay discourse and the channeling effect of judicial review. New York Law Review, 75, 1327–1411.[Web of Science ®] , [Google Scholar]). Our analysis suggests that, despite their claim to neutrality, no promo homo policies are actively harmful both to students who identify as lesbian, gay, bisexual, or transgender (LGBT) as well as to the broader school community. In an effort to ultimately promote healthier, more equitable school environments and experiences for all students, this article aims to raise awareness about the problematic effects of no promo homo policy language and the assumptions that often underlie it.  相似文献