Kinetic and kinematic analysis of stamping impacts during simulated rucking in rugby union     

Bodil Y Oudshoorn  Heather F Driscoll  Marcus Dunn  David James 《Journal of sports sciences》2018,36(8):914-919

Laceration injuries account for up to 23% of injuries in rugby union. They are frequently caused by studded footwear as a result of a player stamping onto another player during the ruck. Little is known about the kinetics and kinematics of rugby stamping impacts; current test methods assessing laceration injury risk of stud designs therefore lack informed test parameters. In this study, twelve participants stamped on an anthropomorphic test device in a one-on-one simulated ruck setting. Velocity and inclination angle of the foot prior to impact was determined from high-speed video footage. Total stamping force and individual stud force were measured using pressure sensors. Mean foot inbound velocity was 4.3 m ? s^?1 (range 2.1–6.3 m ? s^?1). Mean peak total force was 1246 N and mean peak stud force was 214 N. The total mean effective mass during stamping was 6.6 kg (range: 1.6–13.5 kg) and stud effective mass was 1.2 kg (range: 0.5–2.9 kg). These results provide representative test parameters for mechanical test devices designed to assess laceration injury risk of studded footwear for rugby union.  相似文献   

Threshold frequency of an electrically induced cramp increases following a repeated,localized fatiguing exercise     

Marcus B. Stone  Jeffrey E. Edwards  Kellie C. Huxel  Mitchell L. Cordova  Christopher D. Ingersoll  J. Patrick Babington 《Journal of sports sciences》2013,31(4):399-405

Abstract

Though clinical observations and laboratory data provide some support for the neuromuscular imbalance theory of the genesis of exercise-associated muscle cramps, no direct evidence has been published. The purpose of this study was to determine the effect of local muscle fatigue on the threshold frequency of an electrically induced muscle cramp. To determine baseline threshold frequency, a cramp was electrically induced in the flexor hallucis brevis of 16 apparently healthy participants (7 males, 9 females; age 25.1 ± 4.8 years). The testing order of control and fatigue conditions was counterbalanced. In the control condition, participants rested in a supine position for 30 min followed by another cramp induction to determine post-threshold frequency. In the fatigue condition, participants performed five bouts of great toe curls at 60% one-repetition maximum to failure with 1 min rest between bouts followed immediately by a post-threshold frequency measurement. Repeated-measures analysis of variance and simple main effects testing showed post-fatigue threshold frequency (32.9 ± 11.7 Hz) was greater (P < 0.001) than pre-fatigue threshold frequency (20.0 ± 7.7 Hz). An increase in threshold frequency seems to demonstrate a decrease in one's propensity to cramp following the fatigue exercise regimen used. These results contradict the proposed theory that suggests cramp propensity should increase following fatigue. However, differences in laboratory versus clinical fatiguing exercise and contributions from other sources, as well as the notion of a graded response to fatiguing exercise, on exercise-associated muscle cramp and electrically induced muscle cramp should be considered.  相似文献   

Effect of cluster set configurations on power clean technique     

Justin P. Hardee  Marcus M. Lawrence  Kevin A. Zwetsloot  N. Travis Triplett  Alan C. Utter 《Journal of sports sciences》2013,31(5):488-496

Abstract

The purpose of this investigation was to examine the effects of cluster set configurations on power clean technique. Ten male, recreational weightlifters performed three sets of six repetitions at 80% of one repetition max with 0 (P0), 20 (P20) or 40 seconds (P40) inter-repetition rest. During the first and second set of P0, the catch and first pull were in a more forward position during repetition 6 as compared to repetition 1, respectively. During the second set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the second pull and the loop. During the third set of P40, differences in horizontal displacement were found between repetitions 1 and 6 for the first pull, transition, and beginning of the second pull. No differences in horizontal displacement were found between repetitions 1 and 6 during P20. During each set of P0, vertical displacement decreased between repetitions 1 and 6 (1.02 ± 0.07 m vs. 0.94 ± 0.06 m; Mean ± s). Cluster set configurations led to the maintenance of vertical displacement throughout all sets. The results demonstrate cluster set configurations with greater than 20 seconds inter-repetition rest maintain weightlifting technique to a greater extent than a traditional set configuration.  相似文献   

Resource constraints as triggers of radical innovation: Longitudinal evidence from the manufacturing sector     

Marcus Matthias Keupp  Oliver Gassmann 《Research Policy》2013

Despite the significant role of radical innovation as a driver of firm growth and performance, the consequences of resource constraints for radical innovation outcomes remain unknown. Our paper addresses this gap. We combine arguments from entrepreneurship theory and the theory of recombinative innovation to construct an overarching theoretical framework that argues why resource constraints can promote, rather than impede, radical innovation. We then build hypotheses on two specific resource constraints, knowledge and financial, and test these by a lagged-variable random-effects Tobit model with longitudinal data from an exceptionally large and detailed innovation survey. Controlling for absorptive capacity, firm age, and firm growth, we find full support for the hypothesis that knowledge constraints spur radical innovation and partial support for the hypothesis that financial constraints spur radical innovation. We discuss the theoretical significance of these findings and point to managerial implications and paths for future research.  相似文献   

Conveying clinical reasoning based on visual observation via eye-movement modelling examples     

Halszka Jarodzka  Thomas Balslev  Kenneth Holmqvist  Marcus Nystr?m  Katharina Scheiter  Peter Gerjets  Berit Eika 《Instructional Science》2012,40(5):813-827

Complex perceptual tasks, like clinical reasoning based on visual observations of patients, require not only conceptual knowledge about diagnostic classes but also the skills to visually search for symptoms and interpret these observations. However, medical education so far has focused very little on how visual observation skills can be efficiently conveyed to novices. The current study applied a novel instructional method to teach these skills by showing the learners how an expert model visually searches and interprets symptoms (i.e., eye-movement modelling examples; EMMEs). Case videos of patients were verbally explained by a model (control condition) and presented to students. In the experimental conditions, the participants received a recording of the model’s eye movements superimposed on the case videos. The eye movements were displayed by either highlighting the features the model focused on with a circle (the circle condition) or by blurring the features the model did not focus on (the spotlight condition). Compared to the other two conditions, results show that a spotlight on the case videos better guides the students’ attention towards the relevant features. Moreover, when testing the students’ clinical reasoning skills with videos of new patient cases without any guidance, participants studying EMMEs with a spotlight showed improved their visual search and enhanced interpretation performance of the symptoms in contrast to participants in either the circle or the control condition. These findings show that a spotlight EMME can successfully convey clinical reasoning based on visual observations.  相似文献   

Measuring the effect of charter schools on public school student achievement in an urban environment: Evidence from New York City     

Marcus A. Winters 《Economics of Education Review》2012

This paper uses student level data from New York City to study the relationship between a public school losing enrollment to charter school competitors and the academic achievement of students who remain enrolled in it. Geographic measures most often used to study the effect of school choice policies on public school student achievement are not well suited for densely populated urban environments. I adopt a direct approach and measure charter school exposure as the percentage of a public school's students who exited for a charter school at the end of the previous year. Depending on model specification, I find evidence that students in schools losing more students to charter schools either are unaffected by the competitive pressures of the choice option or benefit mildly in both math and English.  相似文献   

The Watch-and-Wait Task: On the reliability and validity of a new method of assessing self-control in preschool children     

Anna Neubauer  Caterina Gawrilow  Marcus Hasselhorn 《Learning and individual differences》2012,22(6):770-777

A preschooler's ability to delay gratification in the waiting task is predictive of several developmental outcomes, despite this task's relatively low reliability level. Success in this task depends on the use of distraction strategies. The new Watch-and-Wait Task (WWT) has been developed to enhance reliability and to investigate whether the waiting situation is equally predictive if distraction from the reward is inhibited. To prevent distraction in the WWT, children were instructed to watch an hourglass run out during the waiting period. In a reliability analysis (n = 31) the WWT showed acceptable retest reliability. In a second study (n = 61), the time preschoolers spent waiting in the WWT was associated with later academic achievement and behavioral problems diagnosed at the end of grade 1, even after controlling for intelligence, gender and age. Overall, the WWT proved to be a reliable instrument predictive of children's behavioral and academic development.  相似文献   

Cognitive preconditions of early reading and spelling: a latent-variable approach with longitudinal data     

Anna-Lena Preßler  Tanja Könen  Marcus Hasselhorn  Kristin Krajewski 《Reading and writing》2014,27(2):383-406

The aim of the present study was to empirically disentangle the interdependencies of the impact of nonverbal intelligence, working memory capacities, and phonological processing skills on early reading decoding and spelling within a latent variable approach. In a sample of 127 children, these cognitive preconditions were assessed before the onset of formal education, whereas reading as well as spelling achievement was measured at the end of grade 1. The findings indicate that working memory does contribute to the prediction of early reading and spelling, and that this contribution outperforms that of general intelligence and phonological recoding from long-term memory during the early steps of reading and spelling acquisition. Moreover, the results show that phonological awareness mediates the effects of working memory capacities on early literacy outcomes. The role of working memory and phonological awareness as key cognitive preconditions of early reading and spelling are discussed.  相似文献   

Real options theory,flexibility and the media industry     

Marcus Dimpfel  Frank Habann  René Algesheimer 《媒体管理杂志》2013,15(4):261-272

Abstract

This conceptual paper is based on two propositions: 1.) An efficient flexibility management is a critical success factor for media companies. 2.) The concept of real options theory (ROT) aims at improving a company's flexibility management. As a consequence, it is analysed how ROT can contribute to the flexibility management in media companies. In this context, two research issues are investigated. First, it is shown that real options as substantiations of flexibility are of great importance for media companies: In doing so, it is outlined that options which focus on a company's fixed costs management and options which aim at improving a company's sales situation are of high relevance for all segments in the media industry. Contrarily, options which focus on a company's variable costs are only relevant for media companies engaged in the print segment. Second, it is illustrated how ROT can contribute to the reactive and proactive management of flexibility in media companies.  相似文献   

Shaping the Agenda of Local Daily Newspapers: A Methodology Merging the Agenda Setting and Community Structure Perspectives     

Maxwell McCombs  Marcus Funk 《Mass Communication and Society》2013,16(6):905-919

Community structure research investigates the influence of the local community and specific demographic groups in the community on the degree of emphasis that particular public issues receive in a local newspaper. In contrast to this internal source of influence, intermedia agenda setting emphasizes the external influence of other news media and the national journalistic culture on the news decisions of local daily newspapers. To invoke a cliché, the agenda-setting and community structure perspectives are opposite sides of the same coin and should be considered in tandem. The research design and procedure for statistical analysis presented here, which involves the simultaneous investigation of the influence resulting from community structure and intermedia agenda setting, is a path for new research that can present a detailed explication of the balance between local and national influence on the issue agenda of local daily newspapers.  相似文献