Vitamin D in relation to bone health and muscle function in young female soccer players     

André Brännström  Ji-Guo Yu  Per Jonsson  Torbjörn Åkerfeldt  Mats Stridsberg 《European Journal of Sport Science》2017,17(2):249-256

The present work investigated serum vitamin D (25(OH)D) status in relation to bone and muscle qualities and functions in 19 female soccer players (13–16 years) resident at northern latitude with very low sun exposure (～32–36?h/month) during winter season (late January to early March). Serum 25(OH)D, parathyroid hormone and bone turnover markers osteocalcin (OC) and beta carboxy-terminal collagen cross-links (β-Ctx), as well as body composition and muscle performance were examined. Hormones were tested using routine laboratory methods. Fat mass, lean mass, and bone mineral density in whole body, as well as femur and lumbar spine were evaluated with dual-energy X-ray absorptiometry. Muscle performance was assessed through isokinetic knee extension and flexion, countermovement jump, and sprint running. 25(OH)D was low (50.5?±?12.8?nmol?l^?1), whereas the values of bone turnover markers were markedly high (OC: 59.4?±?18.6?µg?l^?1; β-Ctx: 1075?±?408?ng?l^?1). All bone and muscle measurements were normal or above normal. 25(OH)D was not significantly correlated with most of the parameters of bone and muscle quality or function, except the knee extension time to peak torque (r ?=??0.50, p?=?.03). In conclusion, the level of vitamin D is markedly low in adolescent female soccer players during the winter in Sweden. However, vitamin D levels did not significantly correlate with measures of bone and muscle except a moderate correlation in time to peak torque in the knee extensors. The practical implication of low vitamin D levels in young growing female athletes remains unclear.  相似文献   

Homotolerance and heteronormativity in Norwegian classrooms   总被引：1，自引：0，他引：1  

Åse R⊘thing 《Gender and education》2008,20(3):253-266

This article is based on classroom observations and discusses sexual education that addresses homosexuality. Tolerance of queer lifestyles as well as support for judicial equality between heterosexual and homosexual couples is generally perceived as being high in the Norwegian political context. Norwegian sexual politics is, however, based on a binary understanding of sexuality, linked to stable and authentic sexual identities, and this perspective is highly influential in Norwegian education on sexuality. Homotolerance appears to be the most prominent ambition when teachers deal with homosexuality in their teaching. Informed by queer theory, I intend to investigate how teaching that sets out to create homotolerance reproduces heteronormativity. I will argue that even though education on homosexuality may create increased homotolerance, the very same education does also marginalise and stigmatise homosexuality as well as reproduce binary and heteronormative concepts of sexuality.  相似文献   

Exploring the minority–majority gap in sport participation: different patterns for boys and girls?     

Åse Strandbu  Anders Bakken  Mira Aaboen Sletten 《Sport in Society》2019,22(4):606-624

Abstract

This paper examines the participation of minority and majority youth in organized sport based on the Young in Oslo 2015 survey (response rate: 72%, N = 9.774). Four possible explanations of the minority–majority gap are introduced: (i) culture, (ii) religion, (iii) discrimination/racism and (iv) class and socio-economic resources. Class and religion are further examined in the paper. Initially, among the boys, there are no differences between the minority and majority groups. When taking socio-economic resources into account, the minority boys have a slightly higher participation rate than the majority boys. Among the girls, the likelihood of participating in sport clubs is considerably lower for those with a minority background than for those with a majority background. The analyses show that socio-economic resources have an effect on both girls and boys and that religious denomination also explains, to some extent, the minority–majority gap that exists among girls.  相似文献   

Reliability and validity of a new double poling ergometer for cross-country skiers   总被引：1，自引：0，他引：1  

Holmberg HC  Nilsson J 《Journal of sports sciences》2008,26(2):171-179

Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50-70% higher than that at the flywheel. There was a high test-retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W x kg(-1)) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.  相似文献   

Exploring the Development of Pre-Service Science Elementary Teachers’ Pedagogical Content Knowledge   总被引：1，自引：0，他引：1  

Pernilla Nilsson  John Loughran 《Journal of Science Teacher Education》2012,23(7):699-721

This paper explores how a group of pre-service elementary science student teachers came to understand the development of their Pedagogical Content Knowledge (PCK) over the course of a semester??s study in a science methods course. At the start of the semester, PCK was introduced to them as an academic construct and as a conceptual tool that they could use to plan for, and assess, the development of their professional knowledge and practice as beginning science teachers. All participants were provided with a tool known as a CoRe (Content Representation) and the manner in which they worked with the CoRe was such that it supported them in planning for and assessing their own learning about teaching elementary science through a focus on the development of their PCK. Through analysis of data derived from the application of a CoRe based methodology (modified and adapted for this study) to the teaching of the science topic of Air, participants?? reasons for, confidence in, and perceived meaningfulness of their learning about science teaching could be examined. In so doing, the nature of participants?? PCK development over time was made explicit. The results illustrate real possibilities for ways of enhancing student teachers?? ongoing professional learning in teacher preparation and offer a window into how the nature of PCK in pre-service education might be better understood and developed.  相似文献   

Skiing     

Johnny Nilsson  Vidar Jakobsen  Per Tveit  Olav Eikrehagen 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):227-236

The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross‐country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: ‘short’, self‐selected (normal) and ‘long’. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self‐selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s^‐1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (F_z), anterior‐posterior (F_y) and medio‐lateral (F_x) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3‐D by an opto‐electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior‐posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior‐posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior‐posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior‐posterior force impulse and velocity.  相似文献   

A new device for measuring ski running surface force and pressure profiles     

Johnny Nilsson  Lars Karlöf  Vidar Jakobsen 《Sports Engineering》2013,16(1):55-59

The pressure/force acting between the running surface of a ski and the snow may indirectly change glide friction. Thus, measuring the pressure/force distribution may be important for a deeper understanding of glide in skiing. The present aim was to construct a device that allowed the pressure/force underneath the ski running surface (SRS) to be recorded. Pressure sensors were attached on top of a platform. Sheets of different materials were used to improve the interaction between the SRS and the sensors. Possible functions of the device are demonstrated in three applications that emphasized comparison of force distribution underneath skis selected for similarity, force distribution under both skis and a single ski as well as backward weight distribution. The results show that the device with the pressure sensors mapped pressure/force distribution underneath the skis in the applications presented, and the system can thus be a useful tool for further optimizing e.g., ski designs.  相似文献   

When Teaching Makes a Difference: Developing science teachers’ pedagogical content knowledge through learning study     

Pernilla Nilsson 《International Journal of Science Education》2013,35(11):1794-1814

It is a common view that developing teachers’ competence to restructure or reframe their knowledge and beliefs is inevitably a complex challenge. This paper reports on a research project with the aim to develop science teachers’ pedagogical content knowledge (PCK) through their participation in a learning study. A learning study is a collegial process in which teachers work together with a researcher to explore their own teaching activities in order to identify what is critical for their students’ learning. During one semester, three secondary science teachers worked in a learning study together with a researcher in a cyclical process in order to create prerequisites and further identify conditions for students’ learning. During the learning study, data were collected from video-recorded lessons and stimulated recall sessions in which the teachers and the researcher reflected on the lessons to analyze their development of PCK, their students’ learning and the impact of that knowledge on their own teaching. The results provide an insight into how the teachers developed their self-understanding in which they questioned their own epistemological beliefs, aims and objectives of teaching and taken-for-granted assumptions about science teaching and learning. As such, the study provides an understanding of teacher professional learning through a careful investigation of how teachers’ PCK is enhanced through their participation in the learning study, and further, how students’ learning might be developed as a consequence.  相似文献   

Making PCK Explicit—Capturing Science Teachers’ Pedagogical Content Knowledge (PCK) in the Science Classroom     

Pernilla Nilsson  Anna Vikström 《International Journal of Science Education》2013,35(17):2836-2857

One way for teachers to develop their professional knowledge, which also focuses on specific science content and the ways students learn, is through being involved in researching their own practice. The aim of this study was to examine how science teachers changed (or not) their professional knowledge of teaching after inquiring into their own teaching in learning studies. The data used in this article consisted of interviews and video-recorded lessons from the six teachers before the project (PCK pre-test) and after the project (PCK post-test), allowing an analysis of if and if then how the teachers changed their teaching practice. Hence, this study responds to the urgent call to focus direct attention on the practice of science teaching. When looking at the individual teachers, it was possible to discern similarities in the ways they have changed their teaching in lesson 2 compared to lesson 1, changes that can be described as: changes in how the object of learning was defined and focused, changes in how the examples that were presented to the students were chosen and changes in how the lessons were structured which in turn influenced the meaning of the concepts that were dealt with. As such, issues for enhancing teachers’ professional learning were unpacked in ways that began to demonstrate, and offer insights into, the extent of their PCK development over time.  相似文献   

Internet Based Activities (IBAs): Seniors' Experiences of the Conditions Required for the Performance of and the Influence of these Conditions on their Own Participation in Society     

Ellinor Larsson  Maria Larsson-Lund  Ingeborg Nilsson 《Educational gerontology》2013,39(3):155-167

The digital gap is a threat to the participation of senior citizens in society, as a large proportion of seniors are not involved in Internet based activities (IBAs). To be able to overcome this disadvantage for seniors, there is a need to both learn more about the conditions that make seniors start performing IBAs and to be able to provide them with the most beneficial professional interventions. The aim of this study was to explore and describe seniors' experiences with IBAs. Qualitative interviews were conducted with 10 seniors (aged: 66–82 years) with a variety of experiences with IBAs, and the interviews were analyzed with the constant comparative method. The results reveal three categories that describe the experiences of the established performers, the new performers of IBAs in the process of starting out, and the nonperformers. The variations in performance were influenced by the meaning that the performance of IBAs had for the seniors. In addition, the seniors were affected by several other conditions—such as the support available in their environment, including access to knowledge—as this could encourage them to develop their performance. Basic aspects, such as having access to a computer and to the Internet had been arranged for the performers of IBAs. The different ways of performing IBAs, revealed in the three categories, influenced how the seniors viewed their opportunities to participate in society. The conclusion highlights the finding that professionals should consider a multitude of conditions when introducing seniors to the performance of meaningful IBAs.  相似文献