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Matej Supej Niels J. Nedergaard Joakim Nord Hans-Christer Holmberg 《Journal of sports sciences》2019,37(6):647-655
Here, we explored the relationship between incline and start strategy during alpine skiing. Eight FIS skiers performed starts on a flat (3°) and steep (21°) incline employing five different strategies. Their times, trajectories and velocities were monitored with a GNSS system and video. A significant interaction was observed between slope incline and start strategy with respect to the skier’s exit velocity (p < 0.001, ?2p = 0.716), but not for the start section time (p = 0.732, ?2p = 0.037). On the almost flat incline, both section time (p = 0.022, ?2p = 0.438) and exit velocity (p < 0.001, ?2p = 0.786) were influenced significantly by start strategy, with four V2 skate-pushes being optimal. On the steep incline, neither section time nor exit velocity was affected significantly by start strategy, the fastest section time and exit velocity being attained with four and two V2 skate-pushes, respectively. In conclusion, these findings demonstrate that the start strategy exerts considerable impact on start performance on almost flat inclines, with strategies involving three or more V2 skate-pushes being optimal. In contrast, start performance on the steep incline was not influenced by strategy. 相似文献
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Mikael Swarén Mikael Therell Anders Eriksson Hans-Christer Holmberg 《Sports Engineering》2013,16(4):255-264
The aim of the study was to develop an objective classification method for cross-country ski poles. A test device was designed to expose different pole models to maximal loading and impact tests. A load cell measured the axial forces in the pole shafts, and a laser distance meter measured shaft deflection when a load was applied via the wrist strap. In the loading tests, each shaft reached a plateau where no more force could be transferred. This maximal force transfer (MFT) value was a characteristic measure for flexural rigidity and thereby also strength. The developed test method enables a loading that is more similar to real-life skiing than a standard three-point bending test. Results show that the introduction of shaft indices for buckling strength is beneficial for comparison purposes. The MFT is a relevant parameter used in the characterization of poles. 相似文献
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Stefan Josef Lindinger Caroline Göpfert Thomas Stöggl Erich Müller Hans-Christer Holmberg 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):318-333
Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9°; 11 km/h). Performance was correlated to cycle length (r = 0.77; P < 0.05), relative leg swing (r = 0.71), and gliding time (r = 0.74), hip flexion range of motion (ROM) during swing (r = 0.73) and knee extension ROM during gliding (r = 0.71). Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r = ? 0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training. 相似文献
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Abstract Accurate time measurement is essential to temporal analysis in sport. This study aimed to (a) develop a new method for time computation from surveyed trajectories using a high-end global navigation satellite system (GNSS), (b) validate its precision by comparing GNSS with photocells, and (c) examine whether gate-to-gate times can provide more detailed information about alpine skiing performance. The results demonstrated small mean time differences with no systematic bias, with a velocity dependent scatter of time differences, which diminished at higher velocities. Furthermore, the multiple gate-to-gate and lag times demonstrated that the GNSS enabled a more detailed analysis compared to photocells. The measurements using GNSS showed high validity and potential as a tool for more specific analysis of performance in skiing. 相似文献
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Jan‐Eric Gustafsson Lena M. Holmberg 《Scandinavian Journal of Educational Research》2013,57(3):191-210
In a study of Gustafsson, Wedman and Westerlund (in press), the vocabulary test (WORD) in the Swedish Scholastic Aptitude Test was found to load both on a general factor (G) and a factor reflecting verbal knowledge (Gc'). Word characteristics were gathered in order to investigate if they can account for the variation in items’ loadings on the G and Gc’ factors. The results indicate that items loading highly on the G‐factor tend to involve words which are of Latin origin, relatively frequent, morphologically varied and abstract. Items loading highly on the Gc'‐factor tend to involve words which are of Swedish origin, relatively frequent and particularly so in fiction, and concrete but not nouns. Knowledge about these relations may be used to construct vocabulary tests which to a smaller or larger extent reflect either G or Gc’. The results, although tentative, may also be useful to shed light on the nature of the dimensions of ability. 相似文献
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Carl Bryan Holmberg 《Communication quarterly》2013,61(2):84-90
Rhetorical critics usually understand political communication as messages in terms of speeches, campaign strategies, and voter behavior. By focusing upon messages, critics have failed to understand political communication as structurally formative of communication. A new methodology is proposed which conceives of rhetorical artifacts as enhancements of political communication. American congressional elections are presented as the artifact to be analyzed from the new perspective. Because the proposed methodology treats congressional elections as a structural genre, the contemporary, technological impact of electronic media can be criticized and compared to the artifact originally invented by the founders; the course they set has been strayed. Implications for political communication and its research conclude that we face what Habermas would call a “legitimation crisis.”; 相似文献
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Margarita Holmberg 《European Journal of Engineering Education》2017,42(4):413-428
The Laplace transform is an important tool in many branches of engineering, for example, electric and control engineering, but is also regarded as a difficult topic for students to master. We have interviewed 22 university teachers from five universities in three countries (Mexico, Spain and Sweden) about their views on relationships among mathematics, physics and technology/application aspects in the process of learning the Laplace transform in engineering education. Strikingly, the teachers held a spectrum of qualitatively differing views, ranging from seeing virtually no connection (e.g. some thought the Laplace transform has no relevance in engineering), through to regarding the aspects as intimately, almost inseparably linked. The lack of awareness of the widely differing views among teachers might lead to a lack of constructive alignment among different courses that is detrimental to the quality of engineering education. 相似文献
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James C. Holmberg Anne Louise Dailey 《Community College Journal of Research & Practice》2013,37(3-4):157-166
ABSTRACT Use of: curriculum definition, outside consultant review, extensive research tied to outcomes assessment, curriculum planning models, time commitment estimation, and human relations/group dynamics in revising a college's entire curriculum is reported. Although all of the above are important, consensus models to include delphi are the critical catalyst. 相似文献